re: faking bit depth
re: faking bit depth
- Subject: re: faking bit depth
- From: Dan Reid <email@hidden>
- Date: Sat, 06 Apr 2002 13:12:32 -0700
On Thu, 28 Mar 2002 08:59:40 -0800, Chris Jordan <email@hidden>
wrote:
>
Dave,
>
>
Unfortunately the faking-bit-depth concept doesn't work. The reason is,
>
if you start with 8 bits per channel, then when you convert to 16 there
>
is no way to "fill in" the rest of the levels that the 16-bit colorspace
>
has available. For example, imagine that your file has pixels at the
>
0,0,0 level and 1,1,1 level in 8-bit; in 16-bit it would convert to
>
0,0,0 and 256,256,256 (out of a possible 65,536 levels per channel), but
>
there would be no way to fill in the spaces between 0,0,0 and
>
256,256,256 to get any use out of those extra levels in 16-bit mode. So
>
your edits in 16-bit will have exactly the same effect as if you had
>
done them in 8-bit, and when you convert back to 8-bit you'll see the
>
histogram is just as broken up as if you had done the edits in 8-bit.
Not if you consider a 256 point curve on a scale of 0 - 65,536. You''
benefit from reduced tonal posterization in 16bit mode. You are correct that
a move of pixel value 1 in 16bit mode really corresponds to a 256 color tint
of 65,536. That's all the tonal resolution Photoshop 6 can handle today.
If your histograms after editing in 8bits look the same as in 16bit mode
then by all means work in 8bits. I personally have found the contrary. Large
color gamut input devices like studio digital cameras retain subtle tonal
gradients in 16bit mode compared to edits done in 8bits. This especially
critical when editing in a color space large enough to contain the camera's
color volume. In 8bits some images just fall apart.
8bits certainly taxes Photoshop a lot less!
--
Dan B. Reid
RENAISSANCE PHOTOGRAPHIC IMAGING
Color Imaging Solutions Provider
http://www.rpimaging.com | email@hidden
Toll Free: (866) RGB-CMYK [ 866-742-2695 ]
Local: (505) 471-4126
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