Dither question

[blt975]

When using the "Save for Web" feature to save an AI image to a GIF, there is no obvious visual difference between the image at 256 colors with 0% dither and at 256 colors with 100%. Nor is there a difference in the file size going from 0% to 100% dither. If I can not tell the difference between 0% dither and 100% dither just by looking at the image, then what advantages/disadvantages are there between the two? Does dithering affect printing in any way? What am I not seeing or realizing? I thought that 0% dither would produce a higher quality image.
In addition, an image I created in Illustrator then saved as a GIF looks HORRIBLE when printed from the web in black and white. I posted the image to the web (color image) then when I printed out the webpage on a black and white Laserjet, it looked very bad. The image was saved as a GIF with 256 colors and 0% dither. The printout is very pixelated and dark. The color image contains a triangle with a blue to white gradient - this triangle looks very bad when printed - the gradient can not be seen - the tip of the triangle is black then changes to white with no fade or gradient.
Any suggestions on the dithering and the printing issue would be greatly appreciated. Thanks.

 

[carlow]

Hi,


I'm ot a specialist o the web building thing, but your question about printing does concern me.
Dithering is a special way to heave clourqs close od the capabilities of an ordinary computer with a simple videao-card..

Printing is toatally diferent.
First of all why would you sae for wed if you wan't to print something. if you sav or web the compression ofthe original file and the dithering applied to it are not very useful for print quality. The best thing to do isthat when you publih a logo or whatever that can also e ownloaded and printed is to have a second version for the download (best is a pdf-format) and ave the cmpressedfile only for iewing on the we/monitor.
Be sure to save your pdf as a print or press optimised.


hope this helps
.. grillhouse

 

[blt975]

Thanks for the response Grillhouse. The reason I am concerned about the print quality from the web is so if visitors to my website want to print one of the website pages, the graphics on the resulting printout will appear as sharp and clean as they do on the screen. Thanks again for the advice.