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

[Omari Stephens <xsdg xsdg org>]

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
> binding"?

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
> proofing.

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
> > > cases.
> > 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.

--xsdg