writes …
am working on a display system which is only capable of displaying a total of 512 colors, i.e. 3 bit/channel. I need to create images to display on this system, what would be the best way to transform a regular 8bit/channel RGB image to a 3bit/channel image? I would also like to point out that the gamut is also quite a bit smaller than for
e.g. the REC709. Any pointers would be helpful.
I don’t know the answers to your questions but since no one else has posted anything I’ll toss out a couple of ideas you might use as starting points … first, the limited gamut … if you know the actual numbers for the primaries, white point, etc you can create a custom ‘working space’ very quickly … just do this (this is in CS, I think it’s very similar from Version 6 onward but there may be slight differences in versions other than CS) … do Edit – Color Settings – in ‘working spaces: RGB’ click the RGB drop down menu and scroll up to ‘custom RGB’, which opens a dialog box with the parameters of your current working space … change these as necessary for your tighter gamut and save it as a NEW NAME (or you risk over-writing your current working space!). You may have to do ‘save RGB’ from the drop-down to get this new custom profile placed correctly in the proper system folder.
Anyway, that will give you a custom working space, now you can do convert-to-profile on the files you currently have to tighten their gamuts.
As for the other part of your Q, "what would be the best way to transform a regular 8bit/channel RGB image to a 3bit/channel image?" …. I don’t know that one either but if faced with this problem two things I’d try are doing Image – Adjustments – Posterize and set the ‘levels’ to 512 (if I understand the Help files right). If you have to do this for a lot of files then just make an action to do it and batch them.
The other thing I’d look at is converting the files to gifs, which are limited to 256 colors max so you lose one bit … I seem to recall you can create a custom palette that’s a best fit for an entire image set, or you can use existing palettes (like say the 216 color web-safe palette that combines the colors that Windows and Macs see in common, IIRC). Dunno if this is the type of thing you’re looking for (neither one is a true 3 bit/channel conversion) but that’s what I’d try, based on my understanding of what you wrote. Hope this helps get you started.
Bill
