PDA

View Full Version : help! Adobe PS 8 and 16 bit modes



ReF
09-05-2005, 03:04 AM
when using Photoshop and working with 16bit images, i notice that there are lot of options such as filters that only work with 8bit images. so obviously we are forced to switch to the 8bit mode under the "Image" drop down list. the question is, if i switch to 8bit mode to use a filter (like barrel distortion correction using Pano Tools) and then switch back to 16bit mode, am i really going back to 16bit mode with all 16bits of info intact, or am i just going back to 16bit mode with only 8bit info? sorry, i don't have a very clear understanding of how that works.

John_Reed
09-05-2005, 08:27 AM
when using Photoshop and working with 16bit images, i notice that there are lot of options such as filters that only work with 8bit images. so obviously we are forced to switch to the 8bit mode under the "Image" drop down list. the question is, if i switch to 8bit mode to use a filter (like barrel distortion correction using Pano Tools) and then switch back to 16bit mode, am i really going back to 16bit mode with all 16bits of info intact, or am i just going back to 16bit mode with only 8bit info? sorry, i don't have a very clear understanding of how that works.If you take an image that's encoded at 16 bits/pixel (I think that's 16 bits per R, G, & B or C, Y, M, & K component of each pixel) and convert it to 8 bits per, it seems to me that you've lost the 16 bit resolution irreversably. If you start with 65,536 levels of graduation with 16 bits, convert to a scale of 256 levels with 8 bits, the finer resolution will be lost if you re-convert from 8- to 16- bits, in my opinion.

ReF
09-06-2005, 04:58 PM
i forgot to mention that switching from 16 to 8 and back to 16 is all done before saving.

but i'm also thinking that the loss is permanant.

anyone else?

D Thompson
09-06-2005, 06:48 PM
My best guess is it's gone once you go to 8-bit. I've got a couple of books on PS and will dig thru to see if I can find out anything for sure.

ReF
09-06-2005, 07:02 PM
thanks guys :)