Imaging for the Web - Basics

The basics

• How many colors (buzzwords: bit depths, 8-bit vs 24-bit, images vs monitor, dithering)





• resolution & size (more buzzwords: pixel, dpi) looks good vs speed



HP scanners - Deskscan uses print path for resolution, type for colors, default to inches instead of pixel




72/75, 96/100, 144/150, 300, 600, 1200, 4800 dpi, how many "dots (pixel, picture elements) per inches"
screen size (9", 12", 13", 14", 15", 16", 17", 18", 19", 20", 21", 24", 32", 34", 37", 40", 42")
512x384, 640x480, 800x600, 1024x768, 1280x1024, 1600x1280, 1920x1600

Screen size is fixed (adjustable)

The higher resolution you scan, less fit in same screen estate or

* simulated
(more screen space need to show same picture)




How much time to download over 28.8/33.6, 56kbps modem?

e.g. 28.8
40 - 2KB - 1sec
80 - 5KB - 2sec
160 - 13KB - 4sec
320 - 35KB - 10sec

• What kind of graphics (buzzwords: file formats, GIF vs JPEG)



CompuServe's GIF - Graphics Interchange Format

loseless, up to 256 colors only





JPEG - Joint Photographic Expert Group

up to 16 million colors






lossy, possible artifact
degradation in multiple edit and saves, save in this format only in final step



* partially simulated