Re: [Gimp-developer] Soft proofing and the GIMP Display Filters and Color Management settings

On 03/11/2014 11:16 AM, Elle Stone wrote:
On 03/10/2014 04:06 PM, Liam R E Quin wrote:
On Mon, 2014-03-10 at 08:55 -0400, Elle Stone wrote:
::snip? SNIP!::
I agree 100% that soft proofing requires the ability to quickly switch
gamut checks on and off, and also quickly enable/disable soft proofing.
+1 although for print work at this point you have to move to Krita or
Photoshop, most likely photoShop with a "preflight" plugin, so that you
can adjust individual plates (e.g. with dodge) for the different ink
colours (CMYK at the most basic, or two plates for a duotone).

The decision is (as I understand it) for GIMP to stay out of the print
shop so this all gets a little fuzzy for me.

I don't know anything about CMYK printing and I've never used the CM+
plugin, so please bear with me while I ask a couple of questions:

Putting *editing* CMYK channels to one side, is it useful to modifythe
RGB channels while soft proofing to a CMYK profile (or even n-channel
profile whether color or black and white)? I thought that was what the
CM+ plugin made possible? Is this an example of what Gez calls "late

early binding == "you send CMYK to the person who prints your work"
late binding == "you send RGB to the person who prints your work, and they convert to CMYK"

You are correct that CM+ supports "separations" (which is the word for looking at each channel individually). But in that case, this would be part of an early-binding workflow, because you're touching CMYK rather than just RGB.

That said, I think your question touches on something that I'm pretty ignorant about, which is how color profiles deal with different numbers and types of channels. I know there is a thing called a GRAY profile, but I have no idea what makes it special or different than a standard profile. Is it basically an RGB profile with R==G==B?

In the New GEGL World, converting between different channel layouts is going to be a reality, and we should at least put _some_ thought into what that means for color management. Of course, this is way out of my depth, and I have no idea.

But there are plenty of non-print use cases for soft proofing, of
course, including e.g. targeting a specific mobile device (even though
there's huge variation between individuals, there are basic limits on
the colour you can usefully work with) or for projection at a conference
or in an art gallery.

There's also converting from a camera input profile to an RGB working
space, and from one RGB working space to another, and from a larger RGB
working space to sRGB for display on the web. Also, some commercial
printers (for example, some print shops with Chromira and Frontier
printers) provide RGB printer profiles to customers to use when soft

These are the usecases that matter to me, so yes :o)

A common way to soft proof requires having the image open twice to
compare the original with the soft proofed version.

Yes. It's unfortunate that Single Window Mode makes this hard.

The current GIMP preferences allow you to choose "Print Simulation" in
"Preferences/Color Management/Mode of operation". But that sets *all*
open images to Print Simulation mode, for which I can't think of any use
No - a display filter makes more sense, agreed. Then you could maybe
make the filter apply be default to all images if you really wanted?
There should be (is??) a way to include something in the title bar
and/or status bar to show which display filters are active.

Having the title/status bar(s) show which display filters are active
would be very useful, especially given that if you close the display
filter window, any activated filters (or deactivated, in the case of the
Color Management filter) are still applied to the image.

Sounds reasonable.


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