Bill said:
What made you start using ProPhotoRGB several years ago? I heard of it
only last week. I don't remember any of my Photoshop books mentioning it.
There is a great deal of information that never makes it into PhotoShop books.
Also, PhotoShop is far from being the only answer in image editing, nor the best
answer, though it is now the most common software in usage. Recall that
PhotoShop is destructive image editing in most of the choices in that interface
and tools set.
I had a problem with out of gamut problems, or just missing colours on offset
prints. One thing that led to was a need for a larger colour space to retain as
much image information as possible. That search led to ProPhotoRGB, which is the
largest generally available colour space. I have to provide images in CMYK, and
using ProPhotoRGB allowed for a very close match, with little to no loss of
colour on most images. I should warn you that some non-PostScript printers
(desktop) prefer RGB information, and using ProPhotoRGB might be too large a
colour space, and not give the best results. Also, images going to newsprint
should use a much smaller colour space, with further limits adjusted on CMYK
output.
Looks like it would absolutely require 16-bit per-channel color support.
There is an older image editing and compositing software called LivePicture.
That allows for high bit manipulation in real time through a proprietary format.
It is easy to work with even 1 GB images on a computer made six years ago. This
software is similar to an earlier edition of Alias Studio, which use to be the
standard of image editing on Silicon Graphics computers. Unfortunately, the
company that produced LivePicture got bought out by another company, who then
decided to stop developing it, and also killed off all MacOS products. With
Alias Studio, the future development became Studio Paint, is still available,
though is very expensive.
I should mention that I rarely do any "adjustments" to images in 8 bit mode. In
fact, I do only a few adjustments in 16 bit mode in PhotoShop (or LivePicture)
to improve CMYK results. Unless I need to do a complex composite image, there is
little need to change to 8 bit mode, except as a final step to place images into
layout software (InDesign or Quark).
It was developed by Kodak. Here's a short introduction to it:
http://www.naturephotographers.net/articles1203/mh1203-1.html
Nice article. Very simple, and not very technical. Kodak does not explain
ProPhotoRGB very well, so for those more interested, that article is a good
starting point.
Dark hues and shadow areas, eh. Thanks for the answers, Gordon!
What the out of gamut warning is often telling you is that a printed image has
too much ink in those areas. The ideas are more discussed if you look into GCR
and UCR as they relate to printing. The basic idea is that the best papers
handle about 300% ink in any one spot (a few can do better, depending upon the
ink and press). So if you consider Cyan, Magenta, Yellow, and Black each at 100%
ink per plate, then that would give you 400%. Even if the RIP allowed placing
that much ink, the paper might buckle, or the ink might smear, or cause other
printed "distractions". So what a RIP tries to do is clip the total ink in any
one area below the limits of the paper and inks (newsprint is much lower than
300%). Almost none of this applies to inkjet printers, unless you have
PostScript colour management driving the printer.
Anyway, the basic idea is that going from RGB to CMYK, there are some colours
(or colour ranges) that do not translate well. Using a large space like
ProPhotoRGB can get you very close. You can always remove colour, but it is
tough to add colour. It has better uses in pre-press preparation than for home
enthusiast use.
As always, glad to be of help. Feel free to ask more questions.
Ciao!
Gordon Moat
A G Studio
<
http://www.allgstudio.com/gallery.html> Updated!
