Color Matching Challenge: correct out of gamut color

[graeme]

Don't know if this is helpful.

I use Vuescan with my ( very cheap ) Canon scanner. It has a scanner profiling option which I used with one of these:

http://www.targets.coloraid.de/

If the endsheets have large areas of flat colour try this:

1. Open the image in photoshop

2. Take a reading of the colour you want to reproduce ( eyedropper / info pallette )

3. Print the image

4. Scan the image in your profiled scanner

5. Open the scan in photoshop

6. Repeat step 2 with the scanned image

7. Create an adjustment layer ( Curves, color blend mode ) and get the color readings as close to the original image as possible.

8. Drag the adjustment layer onto the original file and print.

Before anyone starts screaming at me I don't use this method for photographic images. A few months ago my partner had to present a design to a client ( scanned watercolour ). We wanted a large area of neutral gray around the design. The design was printing out acceptably but the gray had a greenish cast to it, probably due to less than perfect equipment, skills etc and the human eye being sensitive to slight changes in areas of flat colour. I used the above method on the gray area only and it got us much closer.

Graeme

[Bart_van_der_Wolf]

Don't know if this is helpful.

I use Vuescan with my ( very cheap ) Canon scanner. It has a scanner profiling option which I used with one of these:

http://www.targets.coloraid.de/

Indeed, I do the same with all my scanners and VueScan. The targets are relatively reasonably priced.

Cheers,
Bart

[fike]

So it appears that colormunki would be a decent start for doing tasks like this as well as profiling my printers. 

Does the colormunki have software that would allow me to scan a standard color target and then create scanner profiles.  How would I create and in what application would I apply that profile?

[fike]

Well, it is several months later, and I have called this little project done.  I learned  a lot, so let me summarize what I found.

* Some colors really are out of gamut with a particular paper and you will need to use a different (hopefully similar) color. 
* Some papers (in this case a matte, natural book arts paper without any coating) have extremely limited color reproduction range when compared to inkjet photo papers. Profiling a paper/printer combo can't enable it to show every color.
* Using a tool like a colormunki, you CAN read a color and then try to reproduce it, but it looks unnatural. The world has noise.  To make it look somewhat natural, I had to add noise (mostly luminance) to the reproduced image.

So here is what I finally ended up doing.

1) I took the scan I made of the "two color" original (paper color and deep brownish red ink color) and made a mask that I could reapply to a manually generated color background. 
2) I used the colormunki to identify the RGB color values from the paper (there was a range of about six shades of color) 
3) I used that color to fill a layer and then I used the mask created from the scanned version in step 1 to delete the negative space, allowing the paper color to show through.
4) I profiled the book arts paper
5) I printed the image and it looked terrible.  Not anywhere even close to the original.
6) After lots of adjustment layers and soft proofing and out of gamut warnings, I was at my wits end.  I believed that the paper I was given to work with and the printer I had could not reproduce that shade. I was right.  I had been too hard-headed to see what the profiling software was telling me.
7) I added noise, mostly luminance, but some chroma noise too.  this helped immensely.  Because my created shade was all one digitally defined color, and that was out of gamut, I effectively had no pixels to work on to try to get it to look better.  (Is there a way to add noise and to specify the RGB color values you want as, sort-of, seed values for the chroma noise?)
I got close, but not very close.  The uncoated, natural, matte paper just couldn't handle reds very well.

What did I learn:
I think this project taught me a lot more about photographic color management than any photo could ever teach.  In most photos if you used a canned profile, out of gamut colors are rare.  The visual effect is generally subtle, often manifesting itself as a bit of posterization where certain colors are left out of the scene or clumsily overlayed by the printer.  I have mostly seen this in highly saturated yellows and oranges. A minor desaturation of the offending color is usually enough.

As a photographer you have so few instances where you have to deal with major limitations, you kind of don't ever really get the significance of all the things you do in color management.  In this example, PhotoShop's soft proofing capability was really amazing.  It's show paper color function was spot-on.  The out of gamut warning was everpresent, and because of the limitations of the paper, I was dealing with it constantly.  With decent photographic paper, the paper doesn't dramatically diminish the gamut available to you.  I find that soft proofing photo paper profiles to be of limited value, but with this paper soft proofing was extremely valuable.

Everyone should try this exercise.  Get some crappy paper and try to duplicate something from the real world.  It is an eye-opening experience.