Vignettes appear banded

[Joe_leMonnier@adobeforums.com]

Photoshop CS, lots of RAM

I am making some polygon vignettes of a rasterized Illustrator file at 350 dpi and can't seem to get rid of the banding at the edges. Since the image is fairly flat, it is especially noticable .

Within Illustrator, I can get it to work pretty well using opacity masks but my client is on an earlier version that does not support this wonderful feature. So, I turn to photoshop (again) .

Thus far I've tried making layer masks and blurring them, adding a feathered "hole" on a layer above the image and even using a little noise on the layer mask. This last solution of adding noise produces a pattern in the knocked out regions that needs to be masked itself. All in all it seems like I am missing something here very basic, right?

Can anyone help?

[Todie@adobeforums.com]

16 bit per channel might help (if you make the vignette from scratch in Photoshop), finer line screen and higher imagesetter resolution.

I think that Illustrator introduces its own noise to gradations but I'm not sure.

[Chris_Cox@adobeforums.com]

Banding normally means that you're seeing sharp edges -- so adding a small amount of noise can help.

Blurring can actually make the banding worse by creating new sharp edges due to quantization of your display and output device -- sometimes 8 bits/channel just isn't enough.