Fundamentals of Digital Photography

Written for Physics/Sc Ed 423

Let’s count in binary

1 001

2 010

3 011

4 100

5 101

6 110

7 111

8 1000

16 1111 “a nibble”

255 11111111 “a byte” note, 28 = 256

from

Let’s form a black and white picture of 640 x 480 pixels (typical web picture size)

Let every pixel element equal to one byte (256 gray scale, more than ample)

640 x 480 = 307200 bytes; about one third of the size of a floppy disk.

A color picture of the same would be (using 3 bytes per each pixel element to represent the primary colors: magenta, cyan and yellow) 921,600 bytes which is 64% of the capacity of the floppy disk

How is it possible to store larger pictures (e.g. 800 x 600) in color on a single floppy drive? The answer is compression. Compression is the ability to reduce the information in a picture (in terms of the number of pixels) and do be able to decompress the picture when needed.

There are different formats for mechanisms of compression, e.g. tiff, jpeg, bmp, gif. Some tend to decompress more than others.

From: http://www.theimage.com/photography/photopg5.htm

Digital Photography FundamentalsThe mystery of 72 dpi

Key Points of Traditional Photography

From: http://www.theimage.com/photography/photopg5.htm

From: http://www.theimage.com/photography/photopg5.htm

The CCD array. CCD stands for charge coupled display

How useful is digital?

From: http://www.theimage.com/photography/photopg5.htm

Digital Camera Parts

• ccd cell--- replaces the film and is used to create the image, needs some sort of memory

• Shutter--- used to control the amount of light that hits the cells, recovery time between exposures can be long

• Iris--- not always present on a digital camera in fact is fixed

• lens--- used to focus the image on the ccd cell

• iso--- A ccd cell can change its sensitivity to light depending on the bias voltage and can change its color spectrum to white light

Comparing the virtues of digital versus traditional

Comparing virtues -- continued

From: http://www.theimage.com/photography/photopg5.htm

What Megapixel should I shoot at?Ans: It depends what you want the picture for.

From: http://www.theimage.com/photography/photopg5.htm

Humming birds taken at Turkey Run State Park Nature Center with a Kodak DC120 3 megapixel digital camera

Shutter speed not adequate to capture fluttering of humming bird wings

Still Shot, Turkey Run State Park, Trail 3, Kodak DC120 at 3 megapixel

Luminosity Histogram

Original image cropped to 760 x 560 dpi and magnified

The advantage of 3 megapixel pictures

Ability to repair an image using the clone stamp tool in Adobe PhotoShop 6.0. Magnify area first.

Select the Clone Stamp Tool from the toolbar; right mouse click brings up drop down box; select clone stamp tool, place cursor anywhere on picture, right click for drop down box to select area of sampling and stamping, left click anywhere on picture, position mouse cursor to sampling area; use alt left click to sample, place cursor on area to be repaired, left click mouse to stamp; continue as necessary.

After Before