Digital Camera

July 16, 2005

Agenda

Conventional cameras vs. digital cameras Understanding the basic

Image sensors Resolution Capturing color Pixels

What can you do after you take the pictures Selecting a digital camera What else do you want to buy?

Conventional Camera vs. Digital Camera Conventional film camera:

Basic elements an optical element (the lens) a chemical element (the film) a mechanical element (the camera body itself)

Process the film chemically Print it onto photographic paper

Digital Camera Basic elements

An optical element (the lens) A semiconductor device that records light electronically Removable storage device A mechanical element (the camera body itself)

A computer then breaks this electronic information down into digital data You can view the result immediately Print it onto photographic paper via printer Send and store the images digitally

Understand the Basic

Understand the basic Image sensors Resolution Capturing color Pixels

Understand the Basic

Image Sensors A collection of tiny light-sensitive diodes. Diodes convert photons (light) into electrons

(electrical charge). These diodes are called photosites. In a nutshell, each photosite is sensitive to light --

the brighter the light that hits a single photosite, the greater the electrical charge that will accumulate at that site.

A CMOS image sensor

A diode is the simplest possible semiconductor device. A diode allows current to flow in one direction but not the other.

Kodak’s CCD

Understand the Basic Image Sensors

Most common types of image sensors are Charge Coupled Device (CCD) Complementary Metal oxide Semiconductor (CMOS)

Convert light into electrons at the photosites. Think of it as having a 2-D array of thousands or millions of tiny solar cells, each of which transforms the light from one small portion of the image into electrons.

Both CCD and CMOS devices perform this task using a variety of technologies.

The next step is to read the value (accumulated charge) of each cell in the image.

In a CCD device, the charge is actually transported across the chip and read at one corner of the array. An analog-to-digital converter turns each pixel's value into a digital value.

In most CMOS devices, there are several transistors at each pixel that amplify and move the charge using more traditional wires. The CMOS approach is more flexible because each pixel can be read individually.

CCDs use a special manufacturing process to create the ability to transport charge across the chip without distortion. This process leads to very high-quality sensors in terms of fidelity and light sensitivity.

Understand the Basic Difference Between CCD and CMOS

CCD sensors creates high-quality, low-noise images. CMOS sensors, traditionally, are more susceptible to noise.

Because each pixel on a CMOS sensor has several transistors located next to it, the light sensitivity of a CMOS chip is lower. Many of the photons hitting the chip hit the transistors instead of the photodiode.

CMOS sensors traditionally consume little power. Implementing a sensor in CMOS yields a low-power sensor. CCDs, on the other hand, use a process that consumes lots of power. CCDs consume as much as 100 times more power than an equivalent CMOS sensor.

CMOS chips can be fabricated on just about any standard silicon production line, so they tend to be extremely inexpensive compared to CCD sensors.

CCD sensors have been mass produced for a longer period of time, so they are more mature. They tend to have higher quality pixels, and more of them.

Understand the Basic

Digitize Information The light is converted to electrical charge; but the electrical

charges that build up in the CCD are not digital signals that are ready to be used by your computer.

In order to digitize the information, the signal must be passed through an analog-to-digital converter (ADC).

Think of each photosite as a bucket or a well, and think of the photons of light as raindrops. As the raindrops fall into the bucket, water accumulates (in reality, electrical charge accumulates).

Some buckets have more water and some buckets have less water, representing brighter and darker sections of the image.

Sticking to the analogy, the ADC measures the depth of the water, which is considered analog information. Then it converts that information to binary form.

Understand the Basic

The Digitizing Process

135

9238 120

4871 216

8566

Raindrops = Photons of Light

FilterBucket= CCD

ADC – Analog-to-digital Converter to convert raindrop(light) amount to digital info

Understand the Basic

Resolution The amount of detail that the camera can capture

is called the resolution. It is measured in pixels. The more pixels your camera has, the more detail

it can capture. The more detail you have, the more you can blow

up a picture before it becomes "grainy" and starts to look out-of-focus.

Understand the Basic

Capturing Color Each photosite is colorblind. It only keeps track of the total intensity of the light

that strikes its surface. In order to get a full color image, most sensors use

filtering to look at the light in its three primary colors.

Once all three colors have been recorded, they can be added together to create the full spectrum of colors that you've grown accustomed to seeing on computer monitors and color printers.

Understand the BasicHow the three colors mix to form many colors?

Understand the Basic

Capturing Color There are several ways of recording the three colors in a

digital camera. The highest quality cameras use three separate sensors,

each with a different filter over it. Split Beam Spinning Disk Interpolation Bayer Filter Pattern Demosaicing Algorithms

Most consumer cameras on the market today use a single sensor with alternating rows of green/red and green/blue filters (Bayer Filter Pattern).

Understand the Basic Pixels and Resolution

256x256 pixels – 65K total pixels. Very cheap cameras. Picture quality is almost always unacceptable.

640x480 pixels – 307K total pixels. Low end on most "real"

cameras. Great for e-mail and/or post them on a Web site. 1216x912 pixels – 1.1M total pixels. Good resolution for

printing images. 1600x1200 pixels – 1.9M total pixels. “High resolution“ for

printing larger sizes, such as 8x10 inches. You can find cameras today with up to 10.2 million pixels.

Resolution: Printing Pictures

Kodak recommends the following as minimum resolutions for different print sizes:

Print Size Megapixels Image Resolution

Wallet 0.3 640x480 pixels

4x5 inches 0.4 768x512 pixels

5x7 inches 0.8 1152x768 pixels

8x10 inches 1.6 1536x1024 pixels

What Can You Do after You Take the Pictures?

Viewing the Pictures Image Storage Printing the Pictures Fun Projects

View the Pictures Digital cameras on the market today have an LCD

screen, which means that you can view your picture right away.

This is one of the great advantages of a digital camera: You get immediate feedback on what you capture.

Once the image leaves the CCD sensor (by way of the ADC and a microprocessor), it is ready to be viewed on the LCD.

Of course, that's not the end of the story. Viewing the image on your camera would lose its charm if that's all you could do.

You want to be able to load the picture into your computer or send it directly to a printer.

View the Pictures with Fun With the image-editing software that often comes

with your camera you can do lots of neat things: crop the picture to capture just the part you want add text to the picture make the picture brighter or darker change the contrast and sharpness apply filters to the picture to make it look blurry, painted,

embossed, etc. resize pictures rotate pictures cut stuff out of one picture and put it into another "stitch" together many pictures to create one large

panoramic/360-degree picture create a 3-D picture that you can rotate and zoom in on and

out of

Image Storage

Which one shall I buy?

Image Storage There are a number of storage systems currently used in digital cameras:

Built-in memory - Some extremely inexpensive cameras have built-in Flash memory.

SmartMedia cards - SmartMedia cards are small Flash memory modules. CompactFlash - CompactFlash cards are another form of Flash memory, similar to

but slightly larger than SmartMedia cards. Memory Stick - Memory Stick is a proprietary form of Flash memory used by Sony. Floppy disk - Some cameras store images directly onto floppy disks. Hard disk - Some higher-end cameras use small built-in hard disks, or PCMCIA

hard-disk cards, for image storage. Writeable CD and DVD - Some of the newest cameras are using writeable CD and

DVD drives to store images. In order to transfer the files from a Flash memory device to your computer

without using cables, you will need to have a drive or reader for your computer. These devices behave much like floppy drives and are inexpensive to buy.

Think of all these storage devices as reusable digital film. When you fill one up, either transfer the data or put another one into the camera.

The different types of Flash memory devices are not interchangeable. Each camera manufacturer has decided on one device or another. Each of the Flash memory devices also needs some sort of caddy or card reader in order to transfer the data

Image Storage The two main file formats used by digital cameras are TIFF and

JPEG. TIFF is an uncompressed format and JPEG is a compressed

format. Most cameras use the JPEG file format for storing pictures,

and they sometimes offer quality settings (such as medium or high).

The following chart will give you an idea of the file sizes you might expect with different picture sizes.

Image Size TIFF JPEG JPEG

(uncompressed) (high quality) (medium quality)

640x480 1.0 MB 300 KB 90 KB800x600 1.5 MB 500 KB 130 KB1024x768 2.5 MB 800 KB 200 KB1600x1200 6.0 MB 1.7 MB 420 KB

Image Storage

Camera Type File Size* 32MB 64MB 128MB 256MB 512MB 1GB 2GB

2 megapixel 900Kb 35 71 142 284 568 1137 2274

3 megapixel 1.2MB 26 53 106 213 426 853 1706

4 megapixel 2.0MB 16 32 64 128 256 512 1024

5 megapixel 2.5MB 12 25 51 102 204 409 818

6 megapixel 3.2MB 10 20 40 80 160 320 640

8 megapixel 3.5MB 9 18 36 73 146 292 585

The number showed on each cell indicate the images you can save with the memory card.

MB = Megabytes, GB = Gigabytes

* Average file size using cameras highest resolution JPEG mode. The actual number of images per card will vary and depends on the camera model and compatibility of the scene being photographed.

Printing the Pictures Type of printing

Upload to computer and then print to printer Direct from storage device to printer On-line printing service

Snapfish (www.snapfish.com 12 cent/photo + shipping) War-Mart (www.walmart.com Photo Center, order on-line 15

cent/photo & pick up in store) Winkflash (www.winkflash.com with promo 8 cent/photo, 99

cent/shipping) Costco (www.costco.com Photo Center) Shutterfly (www.shutterfly.com ) Kodak Gallery (www.kodakgallery.com )

In-store printing service

Fun Projects

Slide show Greeting card Calendar Poster Invitation MPEG movie

Selecting a Digital Camera

Selection criteria What type of photo I going to take? Does the size of the camera matter to me? What do I do with the pictures?

What do you have to look out when you are shopping for a digital camera? More megapixels, more cropping flexibility Optical vs. digital zoom LCD Image Storage

How do you shop for a digital camera?

What Are You Looking For? Resolution (pixels, imaging sizing selection) Image sensor type (CCD vs. CMOS) Media storage type Shutter speed range, ISO Film speed setting Optical and digital zoom (focus on optical zoom) AF Zoom Recording mode (normal, TIFF, e-mail, Burst shooting) Len and SLR Camera size LCD size Self Timer, flash light, nightshot ability Red eye reduction capability, special effects

Compare Before You Buy It?

Go on-line to do the comparison www.dpreview.com www.zdnet.com www.digicamera.com

Learn more for on-line www.howstuffwork.com for digital camera www.sony.com for Sony 101 www.nikon.com for Digitutor www.canon.com for product descriptions www.bestbuy.com for “compare with products in this pricing

range” (after you select a product)

What Else Do You Want to Buy? Printer

Regular color printer Photo Printer – HP, Epson, Canon and Lexmark

Photo processing software Editing and printing Media management

Other accessory Storage media Additional battery Tripod Camera bag Additional lens Additional flash light

Q & A

Agenda for the Next Session (Aug. 6, 2005)

1. Photo editing Why do I have to edit the photo? What do I need to edit a photo? Basic editing functions Look outs for photo editing

2. Photo printingPrint them yourself or not to print them yourselfCost of printing it yourselfWhat do you need to print a photo?Photo printing alternative

3. Photo project Creating slide showCalendarGift for special occasion

4. Photo archiving and storing