16 bit vers. 8 bit - CanPhoto Forums - Professional Canadian Photography Discussions

Klaus · Dec 2/08, 08:24 AM

Hello Everybody,
Even though there is no doubt in my mind editing in 16 bit, how about storage?
Do I loose quality or colour information if I transfer to 8 bit and later back to 16 bit to do some more work?
Does the repeated transfer between 16 and 8 bit harm the image?
Also - about long term storage. To save space. 8 bit saves me a lot of space, but do I destroy permanently information by doing so - even after bringing back to 16 bit?

Thanks

Klaus

Stephen_Caissie · Aug 14/11, 06:52 AM

Hi, Klaus, I can answer your question. In a nutshell, all your worries are founded, but it may not be as big a deal as you think. Dropping to 8-bit from 16-bit will definitely reduce the quality of your images, but so long as you're doing that at or near the end of your editing process, it shouldn't matter for most images.

16-bit image encoding is most critical on images where you have large areas of almost-identical colour and tone. Think softly-lit skin in a shot for a new brand of foundation makeup. Having a larger number of possible gradations between your black point and white points will allow you to have more subtle shifts in tone without having to rely quite so much on noise to mask any potential banding that can happen if you're applying curves adjustments to either attenuate or stretch out any tonal ranges. (Note that all cameras introduce a small amount of noise anyway, so a perfectly-rendered gradation should never show banding, regardless of the bit depth of your photo; taking that foundation image and rendering it in 8-bit won't change the way it looks to most people.)

If, after dropping the bit depth of your already-edited images to 8bpp, you want to continue editing them, I would say you're fine so long as you're not doing anything involving major curves adjustments. Introducing something like a strong S-curve into a photograph after it's already had some processing is likely to cause any faint artifacts to jump out, and it will have the potential to introduce banding as Photoshop remaps the tones with fewer intermediate steps to help smooth out any sharp transitions.

Stephen_Caissie · Aug 14/11, 06:53 AM

Oh, dang. I just realized this post is from 2008.

Dec 2/08, 08:24 AM	#1
Klaus Member Klaus Rossler Geraldton/Ontario Last Online: Dec 6/08 Join Date: Mar 2005 Posts: 41	16 bit vers. 8 bit Hello Everybody, Even though there is no doubt in my mind editing in 16 bit, how about storage? Do I loose quality or colour information if I transfer to 8 bit and later back to 16 bit to do some more work? Does the repeated transfer between 16 and 8 bit harm the image? Also - about long term storage. To save space. 8 bit saves me a lot of space, but do I destroy permanently information by doing so - even after bringing back to 16 bit? Thanks Klaus __________________ *Klaus Rossler* "In order to really see, we must forget the names of what we are looking at" (Claude Monet)

Aug 14/11, 06:52 AM	#2
Stephen_Caissie Member Stephen Caissie Toronto Last Online: Apr 25/13 Join Date: May 2011 Posts: 69	16 bit vs. 8 bit Hi, Klaus, I can answer your question. In a nutshell, all your worries are founded, but it may not be as big a deal as you think. Dropping to 8-bit from 16-bit will definitely reduce the quality of your images, but so long as you're doing that at or near the end of your editing process, it shouldn't matter for most images. 16-bit image encoding is most critical on images where you have large areas of almost-identical colour and tone. Think softly-lit skin in a shot for a new brand of foundation makeup. Having a larger number of possible gradations between your black point and white points will allow you to have more subtle shifts in tone without having to rely quite so much on noise to mask any potential banding that can happen if you're applying curves adjustments to either attenuate or stretch out any tonal ranges. (Note that all cameras introduce a small amount of noise anyway, so a perfectly-rendered gradation should never show banding, regardless of the bit depth of your photo; taking that foundation image and rendering it in 8-bit won't change the way it looks to most people.) If, after dropping the bit depth of your already-edited images to 8bpp, you want to continue editing them, I would say you're fine so long as you're not doing anything involving major curves adjustments. Introducing something like a strong S-curve into a photograph after it's already had some processing is likely to cause any faint artifacts to jump out, and it will have the potential to introduce banding as Photoshop remaps the tones with fewer intermediate steps to help smooth out any sharp transitions.