Re: 16 bits = 15 bits in Photoshop?
Re: 16 bits = 15 bits in Photoshop?
- Subject: Re: 16 bits = 15 bits in Photoshop?
- From: Jeff Schewe <email@hidden>
- Date: Fri, 22 Apr 2005 01:29:17 -0500
Jim Rich said:
> It makes sense to capture everything as high bit images.Everyone seems to
> agree on this.
> Save the high bit parent file in your archive.
> Create derivative 8 bit files from the parent file for production.
> Use Adjustment layers.
> If the 8 bit file breaks ( as they can in rare cases), then go back to
> the parent 16 bit file and use the previous Adjustment Layers.
While it sounds like a nice middle of the road solution, I would argue a
different slant.
I agree with the capture in high bit.
But I would argue that it critical than ALL MAJOR tone and color moves be
done in 16 bit. Ideally with Adjustment Layers for the simple reason that
setting black & white points (unless you do it accurately in say Camera Raw)
are the tip of the spear so to speak. Major gamma adjustments are second,
such as when you stretch one area and compress another area of the image's
histogram.
I would also argue that depending on the color space you may be in while in
16 bit, it would be a good idea, if at all possible, to do any major color
transforms while in 16 bit.
The aim I try to do is to get the file to the "perfect 8 bit" file, while
still in 16 bit. Then and only then will I drop it down to 8 bit.
I agree that for most purposes, an 8 bit/channel file is all you really need
to produce good gradations from black to white.
The big problem I've personally have over the years when working from
scratch in 8 bit, is there's just no telling what operation or what little
tweek will be the one that is the tipping point for the 8 bit failure.
Granted, as a photographer, it's VERY routine and using to do a lot of soft
edged selections and gradient based adjustments. At lot of the problems
people have with banding is NOT caused with the RGB image banding, it's
caused by creating a soft edged selection as a channel and then really
working on that channel. While an 8 bit/channel RGB does hold up remarkably
well, it's the darn channels in 8 bit that can completely fall apart. Then
the channel, turned into a selection will itself be a primary source of
banding introduced into the RGB file. The banding may NOT be the result of
the actual image adjustment, but the selection with banding, that the
adjustment was made from.
The point that various people decide to drop from high bit to 8 bit will
depend largely on what they are doing and how they are doing it. Personally,
I try to keep it 16 bit as long as possible, but if I'm doing an extensive
retouching job with a ton of layers, it'll get dropped into 8 bit/channel
pretty darn quick. Particularly when I've already made all my major tone&
color most while in 16 bit!
Regards
Jeff Schewe
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