Out of gamut

[b60]

Gimp 2.8, using soft proofing via Color Management in Edit. I set the monitor profile and the ICC values for the printer and paper. The printer I use uses only sRGB. On some of my photos there are quite a bit of out-of-gamut sections. is there a fix for this? I've read that converting to CMYK and then back to sRGB will solve it, but I don't know how to do this in Gimp?

Thanks in advance for any help!

[rich2005]

Quote:...I set the monitor profile and the ICC values for the printer and paper. The printer I use uses only sRGB.

That is sRGB images. Is this a 'home' printer or a printing service? The inks will be CMYK and the printer software provides the conversion.

The difference between sRGB (monitor display) and CMYK (printed colours) shown in the diagrams here https://en.wikipedia.org/wiki/Color_space You have fewer available colours with CMYK mostly the bright colours, blues & greens.

There is a lot of information here: https://www.cambridgeincolour.com/color-...inting.htm but it is a bit technical.

Quote:On some of my photos there are quite a bit of out-of-gamut sections. is there a fix for this? I've read that converting to CMYK and then back to sRGB will solve it, but I don't know how to do this in Gimp?

You can convert RGB -> CMYK -> RGB which will reduce the out of gamut colours shown in Gimp. This using a paper .icc profile and Krita for the intermediate conversion.



If you are using Gimp 2.8 (as stated) then the separate+ plugin works. ( I can fix you up with the appropriate files). If you move to Gimp 2.10 then separate+ does not work. There are on-line converters. If you can manage command line then ImageMagick works or use the freeware Krita. Big application just for conversion but that is what is available for free and better than separate+

Is it worth the bother?

What I do, I know the limitations of my computer monitor and software. The monitor has brightness turned down using the simple process here: https://www.cambridgeincolour.com/tutori...ration.htm

Even then, from experience I know the print will be on the dark side. I bump the image brightness up before printing. That gets me (mostly) what I see on the monitor = what the print looks like. Very much rule-of-thumb and all in the eye-of-the-beholder.

[b60]

(10-11-2018, 09:35 AM)rich2005 Wrote:

Quote:...I set the monitor profile and the ICC values for the printer and paper. The printer I use uses only sRGB.

That is sRGB images. Is this a 'home' printer or a printing service? The inks will be CMYK and the printer software provides the conversion.

The difference between sRGB (monitor display) and CMYK (printed colours) shown in the diagrams here https://en.wikipedia.org/wiki/Color_space You have fewer available colours with CMYK mostly the bright colours, blues & greens.

There is a lot of information here: https://www.cambridgeincolour.com/color-...inting.htm but it is a bit technical.

Quote:On some of my photos there are quite a bit of out-of-gamut sections. is there a fix for this? I've read that converting to CMYK and then back to sRGB will solve it, but I don't know how to do this in Gimp?

You can convert RGB -> CMYK -> RGB which will reduce the out of gamut colours shown in Gimp. This using a paper .icc profile and Krita for the intermediate conversion.



If you are using Gimp 2.8 (as stated) then the separate+ plugin works. ( I can fix you up with the appropriate files). If you move to Gimp 2.10 then separate+ does not work. There are on-line converters. If you can manage command line then ImageMagick works or use the freeware Krita. Big application just for conversion but that is what is available for free and better than separate+

Is it worth the bother?

What I do, I know the limitations of my computer monitor and software. The monitor has brightness turned down using the simple process here: https://www.cambridgeincolour.com/tutori...ration.htm

Even then, from experience I know the print will be on the dark side. I bump the image brightness up before printing. That gets me (mostly) what I see on the monitor = what the print looks like. Very much rule-of-thumb and all in the eye-of-the-beholder.

It's a printing service. they request sRGB. I've been researching and some say that the RGB>CMYK>back to RBG is a no-no. I do have my brightness turned down. Since I used a lot of saturation in editing, I'm assuming that the gamut problem is with these colors (?). If I print them as they are, will a green, say, be green but not as saturated as I see on the monitor?

[rich2005]

Quote:It's a printing service. they request sRGB. I've been researching and some say that the RGB>CMYK>back to RBG is a no-no.

I would say that is a very fair comment. I have not even heard of it before, but it will be one way of getting something into Gimp that might resemble the printed image.

Quote:Since I used a lot of saturation in editing, I'm assuming that the gamut problem is with these colors (?). If I print them as they are, will a green, say, be green but not as saturated as I see on the monitor?

Back to:
quote.. Some RGB colors that you can see on your monitor (in particular, blue, green and all bright vibrant colors) cannot be printed and/or replicated with standard CMYK inks. Keep in mind that, when creating a file for print, you should always make the original file in CMYK color mode before starting to work on it...unquote.

Unless you have a properly calibrated monitor and software to use it, Gimp 2.8 might be a little dubious there, it will be a bit of trial and error.

Some printing services (not many) will send a standard printed test image + the image file so you can compare.