1. The human eye

2. What you see l L H

3. Cross Section through the Retina

4. 20/20

5. The sensitivity of this class

6. How big of a picture? u Final size of the image (in) (a x b) u Required resolution (dpi) u Calculate total number of pixels: u a x dpi x b x dpi u Depth of color (B) (doc) u a x dpi x b x dpi x doc u Compression

7. How many words does a picture worth? bits, not Bytes divide by 8! Size of file Modem speed (Kbps) Parity check and package sizes. Picture Words

8. Example: one page of text u PICTURE u 10”x7” at 76 dpi = 404,320 pixels u b&w  1 bit/pixel u 404,320 bits  50 KB (BMP) u With GIF compression  30 KB u TEXT (  850 words) u 45 lines/page (1½ lines at 12 points) u 80 char/line u 45x80 = 3600 char.  3.6 KB u  5 KB / 1000 words. BOTTOM LINE: don’t use pictures if they don’t say 10,000 words!.

9. See for yourself 850 Words Text Document 5K Same document as GIF 27K Same document as BMP 57K Same document as JPG 222K

10. Transmission times: 56 Kbps modem 56 K download 33 K upload Text Document 4K - uncompressed - modem compression helps Picture 32 K - compressed - modem compression slows

11. On-line conversions u http://www.resizenow.com/ u http://www.zamzar.com/