Understanding Digital Images

I really want to get a handle on how images work. I have bits and pieces of info. swirling around, but nothing fits together in a pattern yet. I went to the library and got a beginner's book on Photoshop Elements 4. My husband has had Photoshop Elements 3 for a while, but we both really need to learn.

I will track my progress and do notetaking here. At some point, I hope it will gel.

Embrace the struggle.

raster: = bitmap images. Dots arranged in a grid pattern. larger file sizes. pixels.

vector: equations rather than pixels. Easily scaled. Download quickly.

Choosing Resolutions:

For Web: 72 pixels/inch.

B & W on regular paper: 150 pixels/inch

Color mag. or brochure: 250 pixels/inch

Notes on Digital Images

JPEG vs. GIF

Remember, GIF for illustratins, clip art, and images with large areas of flat color, JPEG's for photos and images with continuous color.

Images should be RGB 24bit when you begin. 24-bit means millions of colors. 8-bit = 256 colors. How do you get your images to be that way? Bit-depth is important when creating the smallest GIF possible.

CMYK = cyan, magenta, yellow, and key black. I believe these are how images are created for print, whereas RGB is for web.

DPI = dots pers square inch.

images for print usually have DPI of 300 to 800 dpi. For web, always change to 72 dpi.

Bit Depth is the number of colors your image contains.

When you use JPEG, make sure you keep a copy of the original somewhere. (It's lossy).

Dithering helps to reduces color banding and flatness. Reduces visual artefacts.

GIFS have capabilities that JPEGS don't, like anmiation and transparency.

JPEGS distort edges where there is a sharp contrast in color.

TIFF is one of the largest files. Why and when would you use it?

Image editing software: PICASA