sp12 focus expose

8/2/2019 SP12 Focus Expose

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Focus


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Lenses

Modern Compound Lens is made up of different kinds of glass ground to

different thicknesses and curvatures.

Good quality lens - better ground glass

Basic Parts:

Focus Ring

Aperture Control Ring

Depth of filed Preview Scale

Distance marker


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As the focal length increases,so does the magnification ofthe scene but the angle of

view narrows


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David Leventhal, Modern Romance


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3 factors that

affect d.o.f.

Aperture

Focal Length

Distance tosubject


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Digital depth of fieldWhy does f/8 give me one depth of field in

my film camera and another when I use

my digital camera?Depth of Field

Depth of field (DOF) is a term which refers to the areas ofthe photograph both in front and behind the mainfocus point which remain "sharp" (in focus).

Depth of field is affected by the aperture, subject distance,

focal length, and film or sensor format.


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same aperture different image sensor size


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Same lens focal length different sensor/film size


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Two major differences between lenses:

Lens Speed - the widest aperture to which the lens diaphragm can be opened, i.e. 2.0

Faster lenses open up to a wider aperture and admit more light; they can be used in

dimmer light or at faster shutter speed.

Focal Length - The focal length of a lens is defined as the distance in mm from the

optical center of the lens to the focal point, which is located on the sensor or film if the

subject (at infinity) is "in focus".


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Normal lens


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Wide


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Telephoto lens


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Fisheye

Macro


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Lightsensi*vematerial=imagesensor

+ memorycard

Createsavirtualratherthanphysicaloriginal


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Imagesensors:

Recordandstoretheimagetobephotographed(withthehelpofthememory

card,ofcourse.)

AtoDconversion-AnalogtoDigitalconversion

Readtheluminanceorbrightnessofthescene

CCD-ChargeCoupledDevice

ThedatecapturedbyaCCDsensorisreadonerowata*me-conveyorbelt

style.

CMOS-complementarymetaloxidesemiconductor

ThepixelsonaCMOSsensorincludeaddi*onalcircuitryforeachpixelthat

convertsthevoltageintoactualdigitaldata.Thedatacanbetransmiedtothe

camerainparallel=fasterdatatransfer.


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LIGHT METER READING!!Built in Camera Meter: reflective -measures the amount of lightreflected from a subject!into the camera!!Its very important to find out howyour camera reads light with itsbuilt in light meter:!Meters read - luminence -!All meters try to read a scene andthen average a middle grey

(18%).!Use an 18% grey card to help youmeter.!!


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Built-in meters:!Averaging meter - reads most of the image area andcomputes an exposure that is the !averaging of all the tones in the scene.!!Center-weighted meter - favors the light level at the center ofthe image, !often the most important part of the meter.!!Averaging and center weighted - averages a scene butgives more emphasis to the !center area of the the viewfinder

!!Multi-segmented meter - divides the scene into areas thatare metered individually and !then evaluated against a series of set patterns stored in thecameras memory. Tries to compensate for brightness of thesky.!!(Spot meter - reads only a small part of an image and is

useful for exact measurements of !individual areas.)!


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MeteringModes:

Matrix:Averagesceneswhereyouwantallareasoftheimagetobeintotheexposure.

Center-weighted:Any*methecameramightbefooled:backlitscenes,mainsubjectoffcenter,darksubjectsagainstlightbackgrounds,lightsubjectsagainstdarkbackgrounds,orlightonlightordarkondark.

Spot:Portraits,backlitscenes,mainsubjectoffcenter

Inmanycamerasthemeterreadingisinfluencedbytheauto-focuszone

usedtofocustheimage.

Howdoyouexposesothatalloftheimagecanbeexposedwell?


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Strategies to either override or adjust your cameras meter

1. Meter a gray target and use the light meter reading to calculate the best

exposure

fill the viewfinder with a gray card or other 18% gray object

press the shutter button halfway down to activate the light meter andhold it at that position to lock the exposure settings

frame the scene the way you want it and press the shutter button the

rest of the way to take the shot

2. Exposure lock:

or AE lock

The AE lock is usually a button that allows you to lock the exposure

setting for as long as you hold it down.

*make sure your target point (18% gray) is both in the same light and the

same distance from the camera as your subject to be photographed.


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Evalua*ng exposure


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Evalua*ngexposure


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Itdependsonwhereyoumeter


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HISTOGRAMSHistogram shows the brightness values of all of the pixels in an image.The height of each bar represents the number of pixels of a given brightness in the

whole photo.

Dark pixels Shadows Black: 0Middle-value pixels Midtones Middle Gray: 128Light pixels Highlights White: 255


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underexposed wellexposed over-exposed


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Unicorn Peak, Thunderclouds


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Shutter speed


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Shutter speed controls time


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Shutter Speed!!Shutter works with the aperture to

determine the amount of light enteringthe camera!!

!!!B 2 1 2 4 8 15 30 60 125 250 500 1000!


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What can you do with a long shutter speed setting?


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Aperture


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Aperture!! !Aperture refers to the size of the lens opening!! !Works like our pupil: wide open lets in more light!! !Size of the aperture is called an f-stop; the term stop! !refers to a change in exposure and is the the ratio between the diameter of

the aperture in the lens and the focal length of the lens. !!On a 50mm lens, f/2 is saying that the diameter of the aperture is 25mm. !

The ratio is this 50/25 = 2.!!f1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22, 32!


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What is F Stop Anyway?


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WhatisF-Stop,Anyway?

F-stopisthefocallengthdividedbythediameterofthelens.

Forexample,a200mmf/4lenswillbe50mmwide.

200mm/50mm=f/4.

Thatiswhyf-stopistypicallywrienasF/4,meaning"focal-lengthover4"or"focal-lengthdividedbyfour".

Wheredothosenumberscomefrom?

Lensesaremarkedwithaseriesoff-stops,eachoneletsinhalfasmuchlightasthepreviousone.

Thelight-gatheringabilityofalensisdeterminedbyitsarea,andf-stopsaredeterminedbydiameter.

Areaisrelatedtodiametersquared.

Theprogressionoff-stops,1-1.4-2-2.8-4-5.6-8-11-16-22-32,arepowersofthesquarerootof

2.


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Depth of Field:The distance between the nearest and farthest points that appear

in acceptably sharp focus in a photograph.

Small Aperture

More depth of field


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Large Aperture

Less Depth of Field


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Shutter speed and aperture!!Aperture controls:!a) how much light coming into the camera through the lens!b) depth of field (the range of area that the image is reasonably in focus)!!!Shutter speed controls!a) How long the light is coming into the camera!b) If an object in front of the camera is frozen or blurred!!


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sp12 focus expose

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