calman user guide v2

CalMAN v2.0 Display Analysis Tool

User Manual and Calibration Guide

© 2005, Bill Blackwell, All Rights Reserved of 39

CalMAN™ v2.0

Display Analysis Tool User Manual and Calibration Guide

CalMAN v2.0 Spyder Manual Display Analysis Tool



Table of Contents Table of Contents 2

Acknowledgments 3

Foreword 4

License Agreement 5

System Requirements 8

The CalMAN™ Toolkit 8

Support 8

Introduction 9

How we see: Divorcing Biology from Physics 9

Measuring Color: the ABCs of XYZ 10

CIE Luv: Perceptual Uniformity 11

Delta E – Twice as Nice 11

Debunking Color Saturation 12

Gamma and Grayscale Tracking: Why we are here 12

Display Gamma: Love the One you’re with 13

Calculating Gamma 13

IRE vs. Percent Stimulus: Stopping the Insanity! 14

References: Where to go to get More Information 14

The Spyder Manual Calibration Tool (CalMAN™) 15

The CalMAN™ Interface 17

Display Information 17

Measurement Data 19

Charts 22

Other Calculations 23

Printing the Results 23

The Basics of Calibrating a Display 24

Beyond Good and Evil: What to do with Brightness and Contrast 24

Clip Happens: Finding the Limiting Color 25

Run Forest, Run: Iterating Through Measurements 28

Run 2, or How to Screw Up Your Display in One Easy Step 29

Seven the Long Way: A Happy Intermediate Point 30

Wrapping-up 34

APPENDIX 1: Measurement Technique 35

Reading off of the Screen for Front Projectors 37

Room Impacts 37

APPENDIX 2: Accessing xyY Data 38




Acknowledgments I would like to thank my wife Robin for her patience and perseverance as I get deeper and deeper

into the home theater hobby. I would like to thank Derek Smith whose brilliant software

engineering has made this version of CalMAN™ possible. Finally, much of the work in

CalMAN™ is based on the published works of giants in the field of colorimetry and video like

Charles Poynton, Bruce Lindbloom and Guy Kuo.




Foreword Most home theater displays, be they direct-view (CRT, LCD or Plasma), rear-projection (CRT,

LCD or DLP) or front projection (CRT, LCD, DLP or LCOS), are set from the factory to

compete well on a busy, and brightly lit, sales floor. As a result, what looks good at the local

Mega Mart probably looks quite a bit different at home, and most assuredly looks different from

what the program’s director, editor and production engineers saw in the studio. This disparity has

led many home theater enthusiasts to want to have their displays calibrated to the same standards

the studios use.

In the past, this has usually meant hiring a technician, certified by the Imaging Sciences

Foundation (ISF). The technician would bring many expensive pieces of equipment to take

measurements and then would make adjustments to the display’s controls, frequently using a

service menu that is unavailable to ordinary end-consumers.

While this process generally produced good results, it was also unappealing to many for a variety

of reasons:

• Cost of the service

• Availability of a technician,

• Desire to do it oneself, or even

• Too high of a churn rate in displays!

The net impact of these things is that there is a latent demand for a high-quality tool that is

affordable to the general home theater enthusiast. However, until recently, the only tools

available to the home theater enthusiast were either targeted at professionals, and were priced

accordingly, or required manually transcribing data from one application window to another.

Enter CalMAN™.

CalMAN™ version 2.0 is the first fully-automated home theater calibration tool designed

specifically with the home theater enthusiast in mind. It has been built from the ground-up with

features to make a professional-quality calibration doable with a hobbyist’s budget and

knowledge. While CalMAN™ users will gain an appreciation of critical home theater concepts

like gamma, color balance and delta E, the tool does not presuppose the user has this knowledge

before beginning the calibration process. That is where this manual comes into play. It is the

starting point to getting the most out of your home theater investment possible.

Welcome aboard!

Bill




License Agreement Please read this license document (the "license") carefully before using the licensed software. By

using the licensed software you accept the limitations and conditions of this license. If you do not

accept these license terms, promptly erase or otherwise destroy the unused software and all

other materials provided with it.

1.0. This license agreement is for the software product commonly known as CalMAN™, a

display calibration software product used in conjunction with a spreadsheet program like

Microsoft’s Excel. Permission is granted to use this software to perform image calibration to

displays that belong to a single user for non-commercial purposes only. Use of this software for a

commercial purpose or for displays not owned by the licensee is strictly prohibited. Various

commercial use licenses are available from the licensor for such purposes.

1.1. Ownership. You acknowledge that Bill Blackwell and his licensors own all rights in the

Licensed Software and Documentation. Other products required to be used in conjunction with

the CalMAN™ Software (such as Microsoft Excel) are the property of their respective owners

and may be protected by other licensing agreements, and by applicable copyright or other law.

1.2. Source Code. As delivered, the software contains all of the necessary calculations and

computations necessary to properly calibrate a display. You agree not to duplicate, replicate or

otherwise transfer the source code of the tool to another product, whether commercial or not.

Distribution of the software or its underlying code or methods to third parties is distinctly

prohibited. The licensee is also prohibited from dissassembling, decompiling or reverse

engineering, in any way the functionality contained within the software.

1.3. Transference. The user agrees not to transfer the software in any form or fashion that

conveys partial or full access to the underlying functionality of the software. Should the user do

this, by willful act or accident, then the user’s license rights are terminated. The licensee is

allowed to sell the rights to his or her license to a third party, provided all tied hardware (see 1.5,

below) is included as part of the sale. Some licensees are prohibited from transferring ownership

in any way by prior arrangement or licensure agreement.

1.4. Printing. The licensee is authorized to create and store “printouts”, either on paper or in

a read-only, secure, typeset-oriented electronic form, such as Adobe’s portable document file

(pdf) form. The licensee is prohibited from republishing all or any portion of the software which

might provide a third party access to any of the software's functions or utilities in any electronic

format not otherwise expressly granted, as above. Where any such authorized printout is made,

all copyright notices of the author must be maintained intact and in their original form.

1.5. Hardware Tie-In. The software is licensed to the licensee based upon his or her

ownership of specific color calibration meters, and the software licensed is irrevocably tied to

those meters based upon their serial numbers. Use of the software while not in ownership of

ALL HARDWARE TIED TO A LICENSE is a violation of this agreement.

2.0. Termination. This License is effective until terminated. You may terminate this license

at any time by destroying the Licensed Software and Documentation, and all copies thereof,

including partial copies. This License will also terminate automatically without notice from Bill

Blackwell or his designees if you fail to comply with any provision of this License. Upon




termination, all rights granted under this License shall terminate, and all complete and partial

copies of the Licensed Software and Documentation must be destroyed.

3.0. No Warranty. THE LICENSED SOFTWARE AND DOCUMENTATION ARE

PROVIDED ON AN "AS IS" BASIS. NEITHER BILL BLACKWELL NOR DEREK SMITH

WARRANT THAT THE FUNCTIONS CONTAINED IN THE LICENSED SOFTWARE

WILL MEET YOUR REQUIREMENTS, OR THAT THE OPERATION OF THE LICENSED

SOFTWARE WILL BE UNINTERRUPTED, ERROR FREE, OR VIRUS-FREE, OR THAT

DEFECTS IN THE LICENSED SOFTWARE WILL BE CORRECTED. THE LICENSOR

EXPRESSLY DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING,

BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY,

FITNESS FOR A PARTICULAR PURPOSE, AND NON-INFRINGEMENT. SHOULD THE

LICENSED SOFTWARE OR DOCUMENTATION PROVE DEFECTIVE, YOU ASSUME

THE ENTIRE COST OF ALL NECESSARY SERVICING, REPAIR OR REMEDIATION

MEASURES. THIS DISCLAIMER OF WARRANTY CONSTITUTES AN ESSENTIAL

PART OF THIS LICENSE. NO USE OF THE LICENSED SOFTWARE IS AUTHORIZED

HEREUNDER EXCEPT UNDER THIS DISCLAIMER.

4.0. Limitation of Liability. UNDER NO CIRCUMSTANCES AND UNDER NO LEGAL

THEORY, WHETHER CONTRACT, TORT, OR OTHERWISE, SHALL BILL BLACKWELL

OR DEREK SMITH BE LIABLE FOR INDIRECT, CONSEQUENTIAL, INCIDENTAL,

SPECIAL OR EXEMPLARY DAMAGES SUCH AS, BUT NOT LIMITED TO, LOSS OF

REVENUE OR ANTICIPATED PROFITS, BUSINESS INTERRUPTION, LOSS OF

BUSINESS INFORMATION, OR OTHER ECONOMIC LOSS ARISING OUT OF OR IN

CONNECTION WITH THIS AGREEMENT, EVEN IF EITHER PARTY HAS BEEN

ADVISED OF THE POSSIBILITY OF SUCH DAMAGES AND REGARDLESS OF

WHETHER ANY REMEDY SET FORTH IN THIS AGREEMENT FAILS OF ITS

ESSENTIAL PURPOSE.

5.0. Governing Law. This License shall be interpreted, construed, and enforced in

accordance with the laws of the State of Texas.

5.1. Severability. In the event that one clause, section or portion of this EULA is deemed

unenforceable, void or negated by a court of law, that shall have no bearing on the validity,

enforceability or duration of the remaining clauses.

6.0. No Other Agreement. This License constitutes the entire agreement between the parties

relating to the Licensed Software and Documentation and supersedes any proposal or prior

agreement, oral or written, and any other communication relating to the subject matter of this

License. If any provision of this License is held to be unenforceable in any respect, such

provision shall be reformed only to the extent necessary to make it enforceable.

7.0. Acknowledgment. You acknowledge that you have read this License, understand it, and

agree to be bound by its terms and conditions. If you do not agree to the terms of this agreement,




then your license right is terminated, and you must destroy the licensed software and

documentation.

CalMAN™ is Copyright © 2005 - 2006 by Bill Blackwell. Some portions of CalMAN™ are

Copyright © 2006 by Derek Smith, and are used under license by Bill Blackwell. All rights

reserved.




System Requirements To use the CalMAN™ tool, you will need to meet the following hardware and software

requirements:

• A desktop or laptop PC (Macintosh compatibility cannot be guaranteed).

• A copy of Microsoft Excel® 2000 or later (1997 should work, but is not supported;

unreleased versions of Microsoft Excel® are also not supported).

• A supported color measuring instrument (please see our website for a complete list of

currently supported meters)

• For front projectors, a tripod is highly recommended.

In addition to the software requirements, you should expect to spend several hours the first time

you use the tool in order to get familiar with taking measurements and analyzing the results. The

average user will take 3 – 4 sessions to calibrate the first display. Subsequent displays should be

much faster.

Windows® and Excel® are trademarks owned by Microsoft Corporation.

The CalMAN™ Toolkit The CalMAN™ package consists of three major pieces:

� The CalMAN™ Analysis Tool – a spreadsheet-based tool to analyze data provided by a

colorimeter

� The CalMAN™ Calibration Guide – this manual

� CalMAN™ Test Patterns – test patterns suitable for use in calibrating a non phosphor-

based display or television

The CalMAN™ system was originally designed for use with the Colorvision SpyderTV® or

Spyder2PRO® (version 2.0 or higher) packages, but has been expanded to include support for

several other meters. We thank Colorvision and GretagMacbeth for their support in helping us

develop the CalMAN™ tool.

Support The CalMAN™ tool is intended for those literate in the use of spreadsheet models and in the use

of their particular home theater display. You are encouraged to send bug reports or notifications

of other errors to [email protected]. CalMAN™ users are encouraged to participate in the forums

at www.calman.tv/forums/ to learn more about calibration and to share tips and tricks with other

CalMAN™ users. Per the license agreement, the provision of the CalMAN™ forums is neither a

guarantee of support nor an expression of any kind of warranty or post-sale service.




Introduction Congratulations and thank you for purchasing the CalMAN™ display analysis and calibration

tool. The purpose of this tool is to help you to calibrate your display to more accurately represent

colors the way that content authors intended them to be represented. CalMAN™ is very flexible

and provides most of the functionality of much more expensive packages at a fraction of the

price. In fact, CalMAN™ includes many cutting-edge features unavailable anywhere else!

Do not worry if terms like “colorimeter” are unfamiliar to you. This guide is intended for the

interested and diligent hobbyist to get up and running as quickly as possible so that he or she can

get back to watching movies, sports, television shows or whatever interests you. However,

understanding how to improve color does require that you gain some background on what,

exactly, color is. To that end, first-time users will want to gain a basic understanding of

colorimetry (the science of measuring color) before proceeding to use the tool.

How we see: Divorcing Biology from Physics

Many people will remember the colors of the physical spectrum from a high school (secondary

school) or university physics class. In such classes, students are taught the mnemonic

“ROYGBIV” for red, orange, yellow, green, blue, indigo and violet. As a result of this training,

people learn that different colors occupy different ranges within the “visible spectrum”, and that

each color is distinct. While this model works great for astronomers studying absorption spectra

for stars, studying human stars through a telescope is generally a fast ticket to a restraining order.

Instead, biology has a different idea of how to handle the visible spectrum, and it is quite a bit

different than what the physicists use.

In the human eye, there are sensors called “rods” and “cones” that are what actually respond to

light with neural impulses. Rods and cones can be subdivided into four different functions. Three

different types of cones are responsible for what we see as red, green and blue. The fourth type

of sensor in the eye; rods, provide humans with their night vision.

Where the biology really leaves the physics behind is in how these sensors respond to the visible

spectrum. Instead of being a broad-based sensor like one might expect from the ROYGBIV

model, the sensors in our eyes essentially respond to a range of wavelengths much like a

bandpass filter would. That is, there is a peak where the individual sensor is most sensitive, and

then sensitivity falls off rapidly for longer and shorter wavelengths. As a result, what we see as

one “color” is actually an amalgamation of wavelengths:

• The color green peaks at around 550 nm, and dominates how humans sense illumination.

• The color blue peaks at around 440 nm. Interestingly, we are least sensitive to blue

intensity, but are more sensitive to color deviations in blue than in either green or red.

• The color red is actually bi-modal (two “humps” in its sensitivity distribution) with the

main peak at around 600 nm, and a smaller peak at around 440 nm.




Collectively, red, green and blue are considered the primary colors in an emissive color model1.

We can then derive secondary colors as combinations of the three primaries:

• Cyan is a combination of blue and green.

• Magenta is a combination of red and blue.

• Yellow is a combination of red and green.

What we perceive as white light is actually all of these primaries combined in a defined

proportion of red, green and blue. Our concept of white is actually relative – the human eye

adapts to its environments and perceives as white the maximum intensity to which it is currently

sensitized. This is why white can be redefined by various standards-setting bodies based upon

their needs. The implication of this is that what we perceive as black is actually the result of no

light being produced, and the color gray actually contains the same mix of red, green and blue –

just at a lower intensity level than the current reference white!

For most displays, the colors of the primaries are relatively fixed by the manufacturer (e.g.,

phosphor colors for CRTs, dichroic filter colors for digital displays). There can be some latitude

here by making adjustments to a display’s primary color matrix, but this is a super advanced

adjustment. On the other hand, the secondary colors can be adjusted by changing the mix of the

constituent primary colors…but more on that later.

Measuring Color: the ABCs of XYZ

Because everybody is slightly different, and each of us probably sees colors in slightly different

ways, the CIE (Commission Internationale de l’Eclairage, the international body responsible for

the measurement of color) established a theoretical model called the standard observer in order

to provide analytical consistency to how colors are measured. As a result, they also established

three baseline measures of color that align with the three color sensors in the human eye: X, Y,

and Z (the capitals matter, by the way):

• X corresponds with the intensity of light perceived (spectral power distribution or SPD)

by the red cones,

• Y corresponds with the intensity of light (SPD) perceived by the green cones, and

• Z corresponds to the intensity of light (SPD) perceived by the blue cones.

The X, Y and Z values are typically presented in either a range (loosely) of 0.0 to 100 (Y is

maximized at 100), or they are scaled down (“normalized”) to 0.0 to 1.0 (again, loosely).

CalMAN™ uses the latter convention. There is a linkage between XYZ and traditional RGB that

is dependent upon the individual color space being used for RGB presentation. In other words,

think of XYZ as the “raw” data, and “RGB” as the finished product (technically, RGB is linear,

and XYZ is not).

While red, green and blue must be added in proportion to create our sensation of the amount of

light present, only Y impacts our sensation of light in XYZ nomenclature.

1 see Poynton’s Color FAQ for more information on emissive vs. absorptive color systems




While XYZ are the basic color measurements, the CIE also developed a Cartesian system for

presenting color information independently of its intensity (the CIE Chromaticity Diagram).

There is a defined algorithm for converting XYZ data into xy coordinates. However, you need to

have the Y data as well to have a complete specification of color.

CalMAN™ works with the software that comes bundled with your meter and uses whatever

format your meter’s software is capable of providing. CalMAN™ then transforms that data into

the XYZ format for further use, completely transparent to you!

The most commonly used version of this two dimensional coordinate system is the one

developed in 1931, and this is the one CalMAN™ uses. On the Chromaticity Diagram, the

primary colors and the white point are presented as points with x and y values (the lower case

matters, and it is definitely confusing while you are first learning this subject!). For North

American and European displays, the standard white point is known as D65, which corresponds

to a coordinate location of xy(0.313, 0.329). However, the coordinates of the primary values vary

from one specification to another. CalMAN™ users will be interested in two of the following

three color standards for use in home theater and video applications:

• ITU-R Recommendation BT.709 (“Rec. 709”) – the standard for both North American

and European high definition television,

• ITU-R Recommendation BT.601 (“Rec. 601”) and SMPTE-C – the standard for NTSC

480i/60Hz standard definition television (SMPTE-C has supplanted Rec. 601), and

• PAL/SECAM – the standard defined by the European Broadcasting Union (EBU) for

576i/50Hz standard definition television.

CIE Luv: Perceptual Uniformity

One major criticism of the 1931 CIE Chromaticity diagram is that the distance between points on

the plane can be more or less noticeable to the average viewer. For this reason, the CIE updated

the 1931 specification with two new, perceptually uniform coordinate systems. These systems,

CIE Luv and CIE Lab, are much more useful in talking about changes in measurements of color.

A full description of these systems is beyond this manual. However, what is important is that

these systems form the basis of measuring color error.

Delta E – Twice as Nice

Color error is measured using two different measures, ∆E* (pronounced “delta E”, and written as

DE or dE) and ∆C* (pronounced “delta C”, and written as DC or dC). While Delta E* and Delta

C* can be based off of either the CIE Luv or CIE Lab coordinate systems (CalMAN™ uses CIE

Luv), their meanings are constant. They measure the error away from a reference for a particular

color. For Delta E*, this includes the grayscale error (Delta L*) as well as the error in hue (Delta

C*). Because of the way that the references are crafted, Delta C* still contains a fair bit of

influence from grayscale issues. As a result, CalMAN™ adheres to using the more common

Delta E* measurement2.

2 CalMAN™ offers user a unique feature that allows Delta E* to be presented in either its “raw” format, or in a gamma-corrected

format, developed specifically for CalMAN™.




Unfortunately, the original specification for Delta E* was not as perceptually uniform as its

authors had intended (see www.brucelindbloom.com for an illustration of this). As a result, Delta

E* was updated in 1994 to a new computation method. While much improved, the textile

industry (CMC) was dissatisfied with the result and crafted its own version.

Since this last version is not widely used in the home theater industry, CalMAN™ computes

both the 1976 and 1994 version of Delta E*. You should have as a goal to get your display’s

Delta E* under both measures (a dE of 4 is considered the limit of perceptibility for moving

video under most circumstances, but this does not always hold true).

Debunking Color Saturation

One concept that people frequently use to describe colors is how saturated they are. In this,

people typically mean how rich and vibrant the colors are. Few people use this term correctly,

since it generally requires measurement to determine fine gradations of saturation.

Saturation is a term to describe how “pure” a color is. In other words, how free is the display of

one primary from the effects of other primaries.

The major factors that influence a display’s ability to present a saturated image are the accuracy

of its primaries and its instantaneous contrast (the ANSI contrast ratio is one method of

measuring instantaneous contrast). From your perspective, the amount and nature of ambient

light in the display’s environment will most likely dictate how much instantaneous contrast a

display is capable of producing (think light reflecting from white walls). This environmental

factor makes comparing color saturation across environments somewhat difficult, especially

when people are comparing moving images and not test patterns.

Despite this environmental influence, there is a way to use the CIE Chromaticity diagram to

“eyeball” whether your display’s primaries are undersaturated, saturated or oversaturated

versus the standard. If the display’s primary color is inside the triangle, then that primary is

undersaturated. If the display’s primary is right on the defined point, then it is saturated. If it is

outside the triangle, then it is oversaturated/

One final note on saturation: there are two color coordinate systems (HSL and HSV) that use

saturation as a coordinate. An interested reader should consult some of the references at the end

of this section for links to learning about these coordinate systems.

Gamma and Grayscale Tracking: Why we are here

The final piece to the puzzle is gamma (γ). As has already been discussed, the eye sees grayscale

by the variations in light striking the retina versus a reference white. However, the eye’s

response to light is non-linear. In fact, the eye’s response to light is logarithmic, much like the

ear’s response to sound pressure.




As a result of this logarithmic sensitivity, the eye must receive increasing amounts of light to

perceive a given increment of increase in light. The curves that represent this function are named

after the exponent, gamma, and are called gamma or degamma curves, depending upon the

context in which it is used. From your perspective, this difference is largely irrelevant.

A display’s gamma function controls how much light it emits to a given amount of stimulus. In

times past, this was largely controlled by the phosphors in the CRTs. Interestingly enough, these

phosphors had a natural gamma of 2.5, which closely approximates the eye’s own response

function. However, with the advent of digital video and digital displays, this 2.5 gamma can no

longer be taken for granted. In fact, the ITU and EBU standards have harmonized on a gamma of

2.2 (with a linear tail) for all major video standards (HD, NTSC, PAL and SECAM). There is

additional correction applied at the camera to maintain an overall system gamma of 2.5, but this

is beyond the scope of this document.

Display Gamma: Love the One You’re With

Given the importance of grayscale tracking to overall image fidelity, it is unfortunate that so

many manufacturers engineer their gamma curves away from standards in order to compete

better on showroom floors. The most frequent abuse is to “crush whites”, or overdrive the top-

end so that the projector cannot put out enough additional white to show differences in shades of

white. Another common issue is to “crush blacks”, or to flatten out the bottom end so that details

are lost in dark scenes that should otherwise be visible (“shadow details”). Both crushed whites

and crushed blacks are highly undesirable in a display, but there are many displays on the market

that do this, and do it in a fashion that might not be apparent until after the return period for the

display is over.

Users whose displays have multiple gamma options will need to assess each one to find the best

match to the established standards.

The easiest way to find out which gamma option to use is to find a reputable review for the

display and look at the published grayscale tracking curves. Does the display have any odd

inflection points at the top or bottom end? Is the gamma coefficient too high (>2.6 for North

American uses, in the author’s opinion)? Is it too low (<2.0)? Is the curve smooth? If there are

any oddities, then as the song says, “If you can’t be with the gamma you love, love the gamma

you’re with.” Or at least something like that!

Calculating Gamma

Because gamma is an exponent, it can be easily solved for using logarithms on a point basis (thus,

the “point gamma” calculation in CalMAN™). However, to come up with a gamma that best

describes the entire gamma curve of a display opens up multiple avenues. CalMAN™ thus uses

two different measures of gamma; the average point gamma and a quasi-regression gamma using

a custom optimization routine. These two numbers will rarely ever be exactly the same, but for

optimal results, they should largely agree (i.e., be relatively close to each other). A wide disparity

in these numbers indicates a problem in either the display itself or the calibration.




IRE vs. Percent Stimulus: Stopping the Insanity!

One final note to close out the introduction to color science that closely relates to gamma and

grayscale tracking; home theater enthusiasts will frequently use the concept of IRE and Percent

Stimulus interchangeably. This is mostly harmless for Japanese and European displays, or

displays connected to PCs. However, strictly speaking, IRE is a measure of voltage (1 IRE =

1/140th of a volt). Where IRE becomes truly abused is when people refer to the amount of light

generated by a display as IRE. Light should be referred to in a standard unit (typically Lux or

Foot-Lamberts), and never in IRE.

NTSC-based displays (both high definition and standard definition) use a 7.5 IRE pedestal (or

“set-up”) for black. In other words, the display responds with its black level when it sees a signal

of 7.5 IRE (~54mV). Both Joe Kane Productions’ Digital Video Essentials and Ovation

Multimedia’s AVIA Guide to Home Theater properly account for the presence of set-up in their

North American (NTSC) editions. When calibrating a display, it is important to know whether

your display has, and test patterns assume, the presence of set-up. CalMAN™ allows users to

easily toggle whether set-up is present or not in the control area of each template. Non-North

American users will generally want to leave set-up off of their calibrations.

To avoid confusion, you should refer to IRE only when talking about analog signal levels or test

patterns authored to produce those signal levels.

References: Where to go to get More Information

As has been mentioned previously, this section is designed to give a CalMAN™ user enough

knowledge to understand what is being measured by the colorimeter. In some cases,

simplifications are used to get past truly overwhelming concepts. Interested readers should

consult the following sources for more information:

• Charles Poynton’s website, which includes the excellent Gamma FAQ, Color FAQ, and A

Guided Tour of Colorspace: www.poynton.com.

• Bruce Lindbloom maintains a site that has some excellent examples of the issues in Delta

E* and explanations of the calculations used in the CalMAN™ tool:

www.brucelindbloom.com.

• Finally, truly interested users should purchase Charles Poynton’s book: Digital Video and

HDTV Algorithms and Interfaces for a thorough explanation of these concepts.

Now, with the background out of the way, here comes CalMAN™!




The CalMAN™ Tool With the basics of color science out of the way, we can turn our attention to the actual use of the

tool to calibrate a display. The tool is designed for you to work from templates that correspond to

the three major display standards used in North America and Europe, or in countries that have

adopted the European or North American standards. The three standards are HDTV (Rec. 709),

North American SDTV (Rec. 601/SMPTE-C), and the PAL/SECAM standard (EBU SDTV). In

addition, a fourth (experimental) template is provided that will give black and white movies a

more sepia-toned look. The templates for use with each combination are summarized in Table 1.

Table 1 Calibration Templates

Display Standard Template

North American and European High Definition Television (ITU Recommendation BT-709)

HD

North American Standard Definition Television (ITU Recommendation BT-601/SMPTE-C)

SD

European Standard Definition Television (PAL/SECAM) PAL

Black and White Movies B&W

You should note that it is probably best to make a copy of the CalMAN™ spreadsheet file before

entering measurement data or making changes. While precautions have been made to prevent

accidents such as altering or deleting formulae or of putting out-of-range values in some fields,

these precautions cannot account for all possibilities that may arise during actual use. As with

any data management best practice, it is better to be safe than sorry!

Getting Started

When you first launch the CalMAN™ tool, you will only be able to see and interact with the

Preferences worksheet. This is to ensure that your meter is both properly licensed and operating

correctly. Once you have validated the meter the first time, you should save the workbook. You

will then be able to open and close the workbook approximately twenty times before having to

revalidate a licensed meter.

Figure 1. The Preferences worksheet controls the global application options.




When you first open the application, you will need to save your meter’s license information:

1. Select your meter from the Active Meter drop-down box. Also, be sure to indicate the port

on which it is connected in the Port field.

2. Enter the license key for the meter in the License Key field. This should have been provided

to you via e-mail shortly after your purchase.

3. Enter the path to your meter’s DLL file in the Path field. The drop-down box contains

several pre-populated options which might or might not be the appropriate choice for your

computer. If the supplied options do not match your system, then press the Find File button.

This will open a standard “open file” dialog box which will allow you to navigate to where

the DLL driver file is located. Once you have identified the appropriate file, click “Open” in

the dialog box to populate the path field and return to the application.

Figure 2. The Find File button provides you a dialog box for finding your meter's driver DLL file.

4. Once you have done all of this, press the Validate button to verify the license and load the

CalMAN hardware interface layer. Follow the instructions from any status messages.

Figure 3. A green check mark and various status messages will indicate successful validation.

5. Press the Save Config button to save your license and path information for that meter to the

application.




Once you have validated your meter, the templates that are the heart of the CalMAN™

application should appear. You are now ready to begin calibrating your display!

Setting Preferences

The CalMAN™ Interface

Each CalMAN™ template is divided into four areas:

• Control area,

• Measurement data and calculation area,

• Reference standard and calculation area, and

• Chart display area

Within each area, cells are color-coded depending upon what is expected of you:

• Yellow cells are where you should enter data specific to your displays,

• Light Turquoise cells are calculated fields which you should not alter,

• Tan cells are standards-based and should generally be changed only once if you are trying

to calibrate to a different specification than what is shipped with CalMAN™, and

• Rose cells are calculated cells which will be altered by macros. To enable the macros,

these cells are open for editing, but should generally not be altered by you directly.

Control Information

The Display Information area is where you enter information about the display being calibrated,

primarily for users calibrating front projectors. It also presents relevant output information about

display brightness, Gamma, and the digital code values to which the display is being calibrated.

Figure 4. The Control Information Area

Target On/Off Contrast Ratio – The on/off contrast ratio represents the brightest the display can

present a full white field and the darkest a display can present black without making adjustments

to any of the display’s controls. This is used to help determine the minimum screen size and

throw distance which can be used with a front projector. A good rule of thumb here is 2/3 of the

rated contrast ratio (CR) for the display, e.g., a 3,000:1 projector should target 2,000:1, since

very few displays achieve their rated CR specifications with accurate colors.




Target Illumination – This is the maximum expected brightness produced by the projector,

measured in lumens (which is closely related to the SI unit candela), after calibration. For digital

projectors, a good rule of thumb is half of the rated light output, e.g., an 800 lumen projector will

probably produce around 400 lumens after calibration. For CRT projectors, you should use ¼ of

the rated output since CRT projectors use a “point” specification, rather than the more rigorous

ANSI-based specification used by current projectors.

The estimated black level is the result of dividing the target illumination by the target contrast

ratio. For a meter to give an accurate reading at low light levels, this value must be greater than

the black level limit for meter. In some cases, this will result in the meter needing to be very

close to the projector (see cell B10 for the minimum distance using the existing throw ratio).

Note: to provide a rough conversion between lux (lumens per square meter) and foot-candles

(candelas per square foot), one can divide foot-candles by 11 (10.8) to give the lux equivalent.

Screen Information is where you can enter their screen data (only 16:9 and 4:3 screen ratios are

supported) to determine how bright their display’s screen is. This set of calculations only works

if you are measuring the projector at the screen. If not, then the luminance/illuminance

measurement provided by the projector will be too high versus what is displayed on-screen.

Reference Black and Reference White are the digital code values that represent black and white.

The standard for North American and European digital video is for reference black to be at

digital 16 (i.e., red, green and blue are all at bit value 16) and reference white to be at digital 235.

Note: To prevent confusion, peak black is at digital 1 (zero is illegal) and peak white is at digital

254 (255 is illegal). The difference between peak and reference black is known as toeroom, and

the difference between peak and reference white is known as headroom.

Set-up (or pedestal) is the voltage level, expressed in IRE at which the display is expected to

render black. This is specific to the North American (NTSC) television standard, but some DVD

players do not include it, or do not have it turned on by default. When set-up is not present, then

the Region 1 grayscale patterns for AVIA and DVE must be recalculated from their shipping

labels. Because of the presence of set-up, it is not appropriate to link IRE values directly to

percentage stimulation.

Target Gamma is the gamma to which you want to calibrate the display. For all current TV

standards, the gamma equations have finally been harmonized (from what the author has been

able to determine). The defined gamma is 1/0.45, or approximately 2.22. That being said, a

CRT’s “natural” gamma is around 2.5, and the original PAL standard used 2.8. For a modern

display, anything between 2.0 – 2.8 should be considered acceptable if it does not have any

irregularities in the curve. As was mentioned previously, many manufacturers “enhance” their

gamma curves with various goals in mind, so the author recommends “smoothness” of a gamma

curve over getting the coefficient itself to match exactly the formal display standards.




Note: To minimize the impact of gamma error on the calculation of color error (delta E), you

will want to set the value of this field to the value in the Actual Gamma field after completing a

measurement run and calculating the gamma.

On/Off Contrast Ratio is the displays on/off contrast ratio as measured.

Actual Gamma displays the result of a regression fit (actually a correlation maximization, but

that is a minor statistical difference) of the displays gamma curve versus an ideal curve. Since

the calculation requires the use of a custom optimization routine, it is not automatically updated

after a measurement run. As a result, you should update this field by pressing the Find Gamma button.

Average Point Gamma differs from the Actual Gamma in how it is calculated. Instead of using a

regression fit for the entire curve, this measure represents the average of the point gamma

calculations. For a well-calibrated display with a smooth gamma curve, this value should more or

less agree (around ±0.10) with the Actual Gamma value. The Standard Deviation and

Coefficient of Variation are statistical measures that indicate how “tight” the point gammas are.

If the Coefficient of Variation is more than about 25%, then that indicates a serious problem.

Ideally, this value would be less than or equal to 5%, but anything less than 10% should be

acceptable.

Display Information Area Macros

Create Worksheet – Creates a copy of the current template. This is the first button to press when beginning a measurement run.

Find Gamma – After completing a measurement run, press this button to update the Actual Gamma field.

Clear Data – After creating a new worksheet, press this button to clear the measurement data for new entries.

Measurement Data

The Measurement Data area is where the data from each measurement run will be entered, and

where the calculations for color error (delta E) are made. This section is further organized into

sub-areas based on the calculations being performed. The top area is used for grayscale tracking

and the bottom area is for measuring primary and secondary colors.




Figure 5. The Measurement Data area




Grayscale Tracking Measurement Data

The first major area contains the reference illumination target for calculating gamma. Here you

can see the conversion between percent stimulus, IRE, digital RGB and the resulting normalized

light output. As mentioned previously, one should note the differences between the digital RGB

values, which should be integers, versus the IRE and percent stimulus values. Where set-up is

present, there is not a clean mapping between IRE and either percent stimulus or RGB

equivalents!

In the remaining part of the grayscale area are six rows of interest:

x, y, and Y is where you should enter the xyY measurement data for each measurement point in

the grayscale. If you are using the included test patterns, then you should use the “digital”

templates. If you are using a third-party set of measurement patterns like AVIA Guide to Home

Theater, then you should use the analog set of templates.

Coordinated Color Temperature is where the color temperature is displayed. CalMAN™ uses a

method known as McCamy’s N to estimate CCT. Other methods can be used, but at the cost of a

significant amount of complexity in the calculation. You should strive to be within 100 – 200

degrees Kelvin of 6504K.

Note: The D65 white point does not actually appear on the 6504K line when CCT is calculated

using McCamy’s N.

∆∆∆∆E* (1976) and ∆E* (1994) are two different methods of calculating color error that are in common use. While both have been criticized for not being quite as perceptually uniform as was

intended, they do frequently return slightly different values for any given measurement point.

Both methods are presented so you can minimize whichever method gives the greatest error at

any given point. The expectation here is that the higher of these two will represent a “worst case”

for color error.

Note: another method of calculating ∆E* has been proposed by a textile manufacturing industry

trade group (CMC), and this is frequently referred to as ∆E*(CMC). Should a video-related

standards body adopt this method as the preferred method for calculating color error, it will be

included in a patch release.

Primary and Secondary Color Measurement Data

In addition to balancing grayscale, one must also balance the primaries against each other to

achieve proper color in the secondary and tertiary colors. CalMAN™ is designed to use full-field,

full intensity test patterns for each of the primaries and secondaries to determine how saturated

and “true” these colors are.




The Reference area contains the defined points in the CIE’s 1931 gamut for each of the primary

and secondary colors. The Y values are presented using normalized values (0.0 – 1.0, inclusive).

The Measured area is where you should enter the x, y and Y data returned for each of the

corresponding colors. Since a 100% white field is measured as part of the grayscale tracking

measurements, that value is carried over. Users who want just to measure primaries and

secondaries should enter the xyY data for white in the 100% stimulus column for grayscale

tracking.

If 100% primaries and secondaries are used, then the ∆E* (1976) value displayed will be correct. However, if 75% patterns are used, e.g., while using Digital Video Essentials, then the color

error calculation will be incorrect.

Note: Should standards-setting bodies update any of the primary or secondary definitions, e.g.,

for implementation of so-called “wide gamut” high definition television, then you can replace the

default values with updated values without any need to change the calculations or other behavior

in the tool.

Charts

Once a measurement run has been performed, CalMAN™ includes many useful charts that

provide a visual representation of the display’s performance. The actual use of the charts is the

subject of the section titled, The Basics of Calibrating a Display, but they are enumerated here to

establish what is included in CalMAN™.

• Gamma (grayscale tracking) – the grayscale curve is presented here, along with the

curves for the individual primary colors.

• Coordinated Color Temperature – the color temperature of the display across the

grayscale. The ideal for a display is 6504K in North American and European standards.

Japanese standards use 9300K.

• Color Balance – The average contribution of red, green and blue throughout the

grayscale. This is the first place to look to see which colors need to be increased and

which need to be decreased.

• RGB Level Tracking – A “histogram” of the color balance at each measurement point is

presented here. If a color is consistently low across the entire grayscale, then the

brightness for that primary may need to be increased. If there is a dip at the higher

stimulus values, then its contrast may need to be increased. If that primary is a limiting

color, then the other colors may need to be decreased to compensate.

• CIE Chromaticity – The CIE’s 1931 Cartesian representation of the color gamut. One

important note, a display’s secondaries should generally fall on the line between its

constituent primaries. If it does not, then this may indicate an error in the measurement

technique. Notable exceptions to this rule are InFocus home theater projectors, which

have special processing on the yellow secondary.

• Delta E – A bar chart showing both the 1976 and 1994 ∆E* values for color error for each measurement point. The goal of calibrating a display is to minimize this error.




Other Calculations

The CalMAN™ tool contains other areas of interest to advanced users, but which the novice user

may find excessively detailed.

• Primary Tracking decomposes the white light into the constituent red, green and blue

primaries.

• Gamma calculations for point gamma and regression gamma show numerically how

much deviation occurs with the display’s gamma.

• Grayscale Targets preset the calculations for grayscale targets in RGB, XYZ, CIELab

and CIELuv color coordinate systems.

• Conversion Matrix contains the coefficients used to decompose XYZ data into RGB. The

matrices used come from www.brucelindbloom.com.

Printing the Results

No matter which template you are using, they are all designed to print on four (4) sheets of 8.5”

x 11” paper (the North American “Letter” size). If you live where A4 is predominant, you will

need to make slight adjustments to the page set-up.




The Basics of Calibrating a Display Finally! What is hopefully the good stuff. Having waded through descriptions of color science

and the CalMAN™ tool’s functionality, we finally get to how to use it. One warning before we

get too far into this topic: there is a tremendous amount of variability between individual

displays. What will be covered here is not the end-all/be-all definitive word on calibrating

displays. Instead, it is meant to give you an understanding of how the CalMAN™ tool can be

used to identify problem areas in a display’s performance, and what steps you can take to

improve them. Good places to discuss display calibration are HT-oriented forums like AVS

Forum (www.avsforum.com).

While the overarching goal for calibrating a display is to eliminate, as much as possible, any

color error from the defined standards, it is hard to do this directly and explicitly. Instead, you

should keep the following points in mind:

• Primary colors should be balanced, regardless of color temperature.

• Gamma curves should be as smooth as possible, without any “lumps” or inflection points.

• Color temperature should be as close to D65 and 6504K as possible (within rounding)

• Contrast should be maximized to give as much dynamic range as possible to the image.

Note: The method used to calculate color temperature in CalMAN™ will equate the D65 white

point with 6504K only using the SDTV standards. The HDTV standard produces a slightly lower

(warmer) color temperature for D65. If you are within ±200K of 6504K, then you are doing

fairly well on the color temperature measure.

Beyond Good and Evil: What to do with Brightness and Contrast

Many home theater displays have a bewildering array of controls that allow you to do everything

from control the shape of the gamma curve to editing the color decoder to altering how the

analog to digital converters work. Other displays only give you access to basic controls like

brightness, contrast, and if they are really lucky, tint and hue. While the plethora of possible

controls is beyond the scope of this manual, you should have a thorough understanding two of

the most common: brightness and contrast.

Simply put, brightness controls the base amount of illumination the display emits when it is

supposed to be showing “black”. Contrast, on the other hand, controls how much brighter the

display is when it shows “white”. When calibrating a display, the idea is to minimize the

brightness, without “crushing blacks” (making dark details indistinguishable), and to maximize

contrast, without “crushing whites” (making bright, highlight details indistinguishable). See

Table 2.

Table 2 Brightness and Contrast

Control Synonyms Used to Calibrate:

Brightness Black Level, Offset, Bias, Cut Low level color balance

Contrast White level, Picture, Gain, Drive High level color balance, Gamma




The limiting factor on how low brightness can be set is the amount of ambient light (or light

floor) there is in the viewing environment. If it is set too low, then low light level details (shadow

details) will be lost. If it is set too high, then scenes that are supposed to appear black will,

instead, appear gray. Since the human eye views grayscale in relation to the surrounding light, in

so long as the display has sufficient dynamic range to give enough contrast between black and

white, color performance will not suffer too much if the viewing environment has some light.

The key is setting up the display for the desired viewing conditions, and then learning to tolerate

deviations during sub-optimal times. Of course, settings memories in the display help a lot here!

Brightness

Contrast

Total

Potential

Illumination

Light

Output

% Stimulus

Figure 6. Brightness and Contrast work together to control illumination.

For CRT-based displays, the display’s ability to increase contrast can be dramatically impacted

by the quality of the high voltage power supply (HVPS). If the power supply is weak, then as

contrast gets to the maximum, the set has trouble maintaining linearity in images. In other words,

straight lines bend. A Needle Pulse pattern is good for diagnosing this type of issue. Something

else for CRT owners to be aware of is blooming (the “dot” getting to be too large). Both AVIA

and DVE do an excellent job of helping diagnose these issues.

As a starting point for calibrating a display, you should either use the wizard included with the

SpyderTV package, or run through the brightness and contrast chapters of your favorite test disc

(like the ones included with CalMAN™).

Clip Happens: Finding the Limiting Color

Once the master brightness and contrast have been set, it is time to get into the brightness and

contrast settings for the individual primaries. This is where the Gamma and RGB Level

Tracking charts become invaluable.




Because green dominates the grayscale, if we just looked at the overall gamma plot, we might

miss issues with the blue and red primaries. However, CalMAN™ plots both the grayscale

gamma curve and the curves for the individual primaries. Thus, we can use the Gamma chart to

identify where inflection points may be occurring with the individual primaries. For lamp-based

displays (e.g., digital front and rear projectors) using high pressure bulbs, as opposed to Xenon

bulbs, the color that tends to clip first is red (see below).

Gamma

0.00

0.20

0.40

0.60

0.80

1.00

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

Percent Stimulation

Luminance

Target

Actual

Red

Green

Blue

Target Gamma = 2.22

Actual Gamma = 2.77

Figure 7. The inflection point in red indicates that this display is near the maximum amount of red it can produce.

In the above chart, the red primary has a clear inflection point in its gamma curve, indicating that

it cannot produce as much red light as is required for that amount of light. Whether this results

from a “feature” introduced by the manufacturer or that the lamp is running out of light is

unknown from this chart. Unfortunately, unless you know what gamma to use (like from other

users or a well-written product review), each gamma should be checked to see which one gives

the best (smoothest, most standards-compliant) curve.




In Greg Rogers’ review of the Optoma H79 in the magazine Widescreen Review, he indicated

that TV Gamma 1 provided the best curve. In checking my unit, I noticed that I was mistakenly

using Film Gamma 1. Thus, I needed to change to the recommended gamma curve and re-

measure.

Gamma

0.00

0.20

0.40

0.60

0.80

1.00

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

Percent Stimulation

Luminance

Target

Actual

Red

Green

Blue

Figure 8. Changing the gamma option to the recommended value eliminates the odd inflection point in the red primary. Red is still clearly clipping at 100% signal levels, though.

With the gamma curve now on the “right” option, I don’t have to worry about trying to correct

the inflection point in the middle of the grayscale. However, the projector still runs out of red

fairly dramatically at high stimulus values. To correct this, either a filter must be used to color

correct the display’s output, and/or I have to change both the brightness and contrast for each of

the primaries (brightness impacts the low-level mix the greatest, and contrast impacts the high

level color mix the greatest).

The odd hitch between 50% and 60% stimulus that was in the initial setting would probably

somewhat unsettling for you. You could clearly see it in both the Gamma curves and the RGB




Levels histogram. Notice that red is more than 20% too low at 60% stimulation. A strong red

filter might help here (e.g., CC20R), but the shape of the irregularity would be hard to eliminate

given most controls that are available to you. Of course, there may be other errors involved as

well (e.g., it may be a sensor error, it may be a measurement technique error, or it may be a

problem with the machine itself).

RGB Level Tracking

0%

20%

40%

60%

80%

100%

120%

140%

160%

0% 20% 40% 60% 80% 100%Percent Stimulation

Red Tracking

Green Tracking

Blue Tracking

RGB Level Tracking

0%

20%

40%

60%

80%

100%

120%

140%

160%

180%


Red Tracking

Green Tracking

Blue Tracking

Figure 9. Changing the gamma curve option eliminated the “hitch” in red (top is before, bottom is after).

Run Forest, Run: Iterating Through Measurements

Once you have determined the limiting color and found the right gamma curve, it is time to go

for trial-and-error on making the changes. Some lucky users will have access to the display’s

service menu that gives them control over a set of master adjustments for each primary that then

affects all of the inputs. If you have access to that menu and set of controls start there. Table 3

shows what I did for my H77.

Table 3 Dialing-in the grayscale requires balancing changes to both brightness (low end) and contrast (high end)

Grayscale Control Run 1 Run 2 Run 3 Run 4 Run 5 Run 6 Run 7

Master Contrast 15 15 15 15 15 15 15

� Red Contrast 146 146 160 130 137 137 135

� Green Contrast 133 133 133 120 115 117 114

� Blue Contrast 134 134 134 120 115 116 112

Master Brightness -3 -3 -3 -3 -3 -3 -3

� Red Brightness 119 119 113 109 114 112 111

� Green Brightness 113 113 113 113 109 110 109

� Blue Brightness 113 113 113 113 109 109 108

Note: The master brightness and contrast were never changed once set initially.




Run 2, or How to Screw Up Your Display in One Easy Step

A good rule for people new to their display’s service menu: if you do not understand a control,

do not touch it. Period. One example of this is playing with controls like the Color Wheel Index

(or CWI) or the DLP brightness and contrast controls. The latter controls impact the DLP itself

and how it responds to signals from the projector’s firmware. However, as Emeril Lagasse might

say, I wanted to “kick it up a notch” to see if this was a shortcut to making my red a little

brighter (for advanced users, I wanted to make the wheel timings a tad more aggressive). To that

end, I increased the red contrast by 10% (from 50 to 55) and decreased red brightness from 50 to

49). The results were very interesting:

CCT looks pretty good for such a quick change:

Coordinated Color Temperature

6504K

3,000

4,000

5,000

6,000

7,000

8,000

9,000

10,000


Color Temperature (K)

Figure 10. Coordinated Color Temperature (CCT) closely matched 6500K.

However, the RGB levels are all over the map: RGB Level Tracking

94%

95%

96%

97%

98%

99%

100%

101%

102%

103%

104%

105%


Red Tracking

Green Tracking

Blue Tracking

Figure 11. The RGB Levels chart indicates that a change in the DLP Brightness and Contrast impacted ALL colors, not just the red primary.




And there is very definitely a problem in grayscale land:

Gamma

0.00

0.20

0.40

0.60

0.80

1.00

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

Percent Stimulation

Luminance

Target

Actual

Red

Green

Blue

Figure 12. Note the impact on blue and green between 80% and 90%.

Fortunately, setting the values back to their original levels cured these problems. It looks like

there is not cheap-and-easy fix for what ails this projector. Also note that this pretty clearly

demonstrates that only looking at one chart as an indicator of performance can leave some pretty

significant errors undetected.

Seven the Long Way: A Happy Intermediate Point

After iterating through several measurement runs to get a feel for how the H77 responded to

measurement changes, I finally achieved what would be a good intermediate point for a

calibration. In other words, a stopping point where the colors are noticeably better, and I can go

to bed satisfied that I had made some real progress. Given the difficulty in calibrating the H77,

this represented about three hours worth of work!




Gamma continues to be smooth, with just a hint of run-out in red…

Gamma

0.00

0.20

0.40

0.60

0.80

1.00

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

Percent Stimulation

Luminance

Target

Actual

Red

Green

Blue

Target Gamma = 2.22

Actual Gamma = 2.92

Figure 13. The gamma value of 2.9 is noticeably different than the standard 2.2.

…but the RGB levels are within 10% from 40% upwards! RGB Level Tracking

0%

20%

40%

60%

80%

100%

120%

140%

160%

180%

200%


Red Tracking

Green Tracking

Blue Tracking

Figure 14. A good goal for RGB level tracking is to have all colors within 10% from 20% upwards. The red primary is still a little excessive at 20%, requiring a further decrease in red brightness.




Also, my yellow is no longer too green; it is instead finally mostly yellow.

CIE Chromaticity

Y

G

R

M

B

C W

0.000

0.100

0.200

0.300

0.400

0.500

0.600

0.700

0.800

0.000 0.100 0.200 0.300 0.400 0.500 0.600 0.700

x

y

Reference

Measured

Rec. 709 coordinates

Figure 15. Most primary and secondary colors are very close to the Rec 709 standard. Red is oversaturated by the manufacturer’s design.

Table 4 Correcting for gamma, only red and magenta show significant color error

Primaries & Secondaries

Rec. 709 coordinates ∆∆∆∆E*

White 4.11

Red 13.79

Green 5.55

Blue 3.82

Cyan (B+G) 1.64

Magenta (B+R) 13.41

Yellow (R+G) 3.33




Once gamma error is factored out, the overall dE numbers do not look too bad, either:

Delta E

0 5 10 15 20

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

DE* (1994)

DE* (1976)

Delta E

0 2 4 6 8 10

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

DE* (1994)

DE* (1976)

Figure 16. The chart on the left represents color error that includes gamma error, and the chart on the right exludes gamma error.

Note: To eliminate gamma error from the calculation of Delta E*, set the Target Gamma field

(L3) to be equal to the Actual Gamma field (L6).

So, where does this leave me? I have much better coloration than I did before, but at the cost of

about 500 points of contrast ratio (~2350:1 � ~1850:1). In order to get gamma under control, the

contrast ratio will have to come down further. Future changes that now can be made:

• Adjusting the red brightness down even more. A few more clicks downwards on red

brightness should have the balance correct at the low end correct.




• Increasing red contrast, but just a hair. This will really only work if lowering the red

brightness frees up headroom in red to allow the contrast increase to be meaningful.

Otherwise, I will have to be satisfied with the slight dip at 100%.

• Finally, gamma needs to be brought within tolerance. The easiest way to do this will be to

tweak the master contrast control down a tick or two at a time. However, it is not

guaranteed that this won’t affect each primary differently, thus throwing off the hard-

earned color balance at the top.

The net result: I expect that the final calibration will come in at around 1500:1, which is not bad

for a bulb with over 500 hours on it (bulbs decrease brightness with age, forcing many users to

increase brightness to compensate at the low end; loss of top-end also hurts the overall ratio).

However, it is far from the specified 3500:1 contrast ratio of the projector itself. You should note,

though, that on/off contrast is a ratio, and in my far-from-light-controlled living room, I have to

have the brightness set much higher than if someone were in a light controlled room (e.g., a

halving of the light output at the low end would double the calibrated contrast ratio). However, I

prefer not to crush my blacks, so an elevated black level is the price I pay for the Wife Approval

Factor (WAF).

Wrapping-up

For me and my H77, the master brightness and contrast controls are input signal dependent.

What this means is that my projector stores settings based upon the input chosen and the signal

fed to the projector. This is actually quite a handy feature, since it means that the projector can be

calibrated independently for almost all of my source equipment (e.g., DVD changer fed via

component, DVHS deck fed via component (HD), HTPC fed via DVI, and HD Tivo fed via

component. The problem is that calibrating this many inputs, well, requires calibrating that many

inputs! This means time!! The good news is that since I started by calibrating my master RGB

gains and biases in the service menu to the HD (Rec 709) standard, I just need to make minor

tweaks to get the calibration correct. A very good thing, indeed.

So, where are we? The net impact is that my projector’s color balance is much, much better. In

fact, in previous viewings, the Lord of the Rings had a very distinctly green cast to it since it used

many vibrant yellows and golds. Now, yellow and gold look like yellow and gold. There is still a

bit of an overemphasized green to the movie, but this was present in the theatrical release as well.

Basically, I like what I see a lot better and so does my wife. Hopefully, you will have similar

success. Best of luck!




APPENDIX 1: Measurement Technique For normal televisions (e.g., anything but front projectors!), measuring the display is a

straightforward activity. The sensor should be centered on the display, hanging “flat” as much as

possible. If you find that the suction cup does not hold the sensor, then consider moving the

counterweight so that the suction cup is holding less of the weight of the Spyder. Also,

moistening the suction cup helps, too!

Figure 17. For direct-view or rear projection sets, the sensor should be in contact with the screen.

For front projection arrangements, you will want a tripod. You will also want a tripod if you are

unable to make the suction cup stick to your screen. When using a tripod, you will want to get

the light grate to be perpendicular to the ground. A torpedo level helps with this, but remember

to take into account that there will be a little bit of “give” from the suction cup. Thus, leveling

the tripod’s “platform” will probably not be sufficient to level the sensor.

Position the tripod so that the sensor is as close to the center of the screen as is possible, on a line

from the lens center of the projector. Some newer digital projectors have high enough contrast

ratios that you may have to move the tripod/sensor closer to the projector than if it is even with




the screen. In that case, you need to know your throw ratio and distance to the tripod to make the

Foot-Lamberts calculation come out correctly.

Figure 18. Digital front projectors will generally be measured directly from the projector. CRT front projectors MUST be read off of the screen.

Figure 19. There will be a little "give" to the suction cup, so account for it when aiming the sensor.




Reading off of the Screen for Front Projectors

Screens that have much gain or coloration (i.e., most anything that is not matte white – the

Stewart StudioTek being theoretically the exception) will impart some coloration to the image.

As a result, front projector owners frequently want to calibrate their projector and screen

combination. This requires setting the Spyder to read reflected, rather than direct, light. To do

this, follow these steps:

1. Set-up the tripod next to the screen with the sensor positioned in the middle of the screen as above.

2. Set the Spyder so that it faces the screen and is angled at 45 degrees. 3. Lower the mast of the tripod until the sensor is low enough that it is aimed at the center

of the screen, with no shadows in the way.

When measuring off of the screen, you should be very patient with low light level measurements.

I have found that measuring 0% signal levels can take several minutes to return an acceptable

reading.

Room Impacts

Folks who have dedicated theaters know that any amount of ambient light can impact the image.

However, the effects of the room go far beyond this. Here are some typical room issues and how

they impact the image:

� Ambient light – raises the light floor and thus, reduces contrast if the display’s light floor

is not higher than the amount of ambient light.

� White walls/ceiling – the walls and ceiling of your home theater can reflect light back

onto the screen, even if there is no other source of illumination in the room. This reduces

the ANSI (instantaneous) contrast of your display, though it does not impact the on/off

contrast too much.

� Bias lighting – This actually helps the perceived contrast by putting a light source behind

the screen which constricts people’s irises. However, the elevated light floor can still rob

some of the on/off contrast.




APPENDIX 2: Accessing xyY Data If you own the SpyderTV, you will need to enable the support mode to access the xyY data

needed to make SpyderMAN work. To do this:

1. Right click on your desktop, and select New �� Shortcut from the context menu.

2. In the Create Shortcut dialog box, click Browse and navigate to where the SpyderTV

executable was installed on your computer. The default is C:\Program

Files\SpyderTV\SpyderTV.exe.

3. After the path to the executable, and outside the quotations, add the /support switch:




4. Click Next and enter a name for the shortcut (e.g., SpyderTV – Support), and then click

Finish to finish creating the shortcut.

5. Double-clicking on the new shortcut will open the SpyderTV with the support window enabled.

6. Change the default Reading Time from 4 seconds to 9 to get better low-light accuracy.

7. When you need to take a reading, just click Single Reading, wait a bit for the sensor to

take the measurement, and then copy the data into the appropriate cells in the tool.

For Spyder2PRO Studio owners, you can get the xyY data from the colorimeter window by

selecting the Tools �� Colorimeter menu option.

Figure 20. The Spyder2PRO Colorimeter tool provides extensive colorimetry data.

calman user guide v2

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