wrote:
In message ,
"David J Taylor"

wrote:

You mean that the 8-bit TIFF is gamma-corrected as well as the JPEG,
and that at the range in the TIFF from lowest brightness levels to
the highest exceeds that of a 12-bit RAW file?

From what I've seen and heard, a TIFF is more likely to be literal in
it's 2.2 gamma in the shadows, whereas a JPEG is more likely to render
the deeper shadows even deeper, to hide noise.

12-bit - 4096 linear levels from 0 to 4095 - range 4095:1

Yes, literally; level 4095 is 4095 times as bright as level 1.

8-bit gamma corrected, 255 levels from 5E-6 to 1 (or 0.001 to 255) -
range 200,000:1

In therms of luminance, it is actually (255^2.2):1 or 196,965:1.

Thanks, John. Our understanding is the same, then. I only quoted
200,000:1 simply because if I quoted the exact number I expected someone
to think I was being pedantic! I can appreciate that JPEG might be
optimised in a slightly different way to TIFF so that errors are masked.

By the way (for anyone else who's still reading), this 2.2 gamma figure is
what some cameras call the "contrast" setting - use a smaller number when
converting from linear to JPEG and you'll get more contrast, a larger
number gives less contrast.

David