Alley in Pisa, Italy

by Lars Kotthoff

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If you look at a source like Library of Congress royalty free gallery, they go an extra step beyond just dumping a bunch of images, but provide them with Kodak Color Control Patches. This is nice, since I'm assuming it should allow me to reconstruct the exact appearance of the images. The problem is I have no idea how to use them properly.

I'm assuming there is some plug-in somewhere in Photoshop or some such program that you can point at the reference colour and grayscale blocks it will do the adjustments for you. But I have no clue how exactly to do it or where/what that plug-in or app is. Such app would also have to know what those colours are supposed to be as opposed to what they appear as on the image, but I'm assuming there should be a standard for this. Does anyone have any experience with this and can point me in the correct direction (a tutorial would be most welcome).

Update: Since I didn't realize that there are 2 interpretations for my question, I will clarify:
I was not hoping that I could use the patches to restore the print to what it looked like when the artist created it, but that I could use them to remove whatever effect the camera/lighting/environment added or took away from what the picture actually looks like at the moment it was photographed.

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Those patches are used for printer/press calibration. The grey scale is used to control the exposure, contrast and dot bleed of the separations (each of the greys should be visible and distinct; the white should be paper-white and the black should be solid) and the colour patches should result in each plate showing only the colours it's supposed to show. The magenta plate, for instance, should show a "black" value for the magenta, red and blue patches with little or no density on the cyan, green or yellow patches, while the yellow should show "black" on the yellow, red and green patches with nothing in the cyan, magenta or blue areas. (It won't be perfect in this case because the Kodak cards are in really, really rough shape.)

You can use the same patches to create a custom colour profile for the image on your own printer if you have a hardware calibration tool like Xrite's ColorMunki. Or you can eyeball the patches on test prints while making colour adjustments to the image onscreen using your own copy of the Kodak cards for comparison.

The point is that the colour patches aren't there for restoration, they're there for print fidelity. You can sort of use them for restoration of old prints, but only if the colour patches are part of the original picture and are not hidden under mattes or frames -- the colour patches would need to have faded and stained to the same degree as the rest of the picture.

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I still don't why the Library includes them in the images then. Or am I just missing the point? Do they plan on using them to reprint the images if they needed to one day? –  dpollitt Dec 11 '11 at 3:30
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Well, they can reprint for display and they'd want the exposed work to represent the original sitting safely in the archive as faithfully as possible. (You're allowed to reprint at will as well). They can also make a future, higher-resolution digital scan of the original work match the colours in the photograph even if the photograph and the original have both faded. The photo is an old silver halide number -- it was expected to degrade over time. The digital scan of the photo probably shouldn't. –  user2719 Dec 11 '11 at 3:45
    
@Stan the patches do not look like they are part of the picture, but rather were added for the photo. So I was not hoping to restore the print to what it looked like when the artist created it, but that I could use them to remove whatever effect the camera/lighting added or took away. Is that possible (if yes, how)? That was the core of my original question. –  Alex K Dec 11 '11 at 14:20
    
@AlexK The file is already what it's supposed to be -- the magenta is magenta, the blue is blue, etc. It was corrected before you got the file. The patches are there (if you grab the version that isn't cropped) to help you reproduce the work as a print. –  user2719 Dec 11 '11 at 14:28
    
@Stan Does it say so anywhere and I missed it? I mean the 2 version (the one with patches vs without) look very different. Which one is correct for monitor viewing (I don't intend to print, but with properly calibrated monitor, I would've thought the differences would be minor). –  Alex K Dec 11 '11 at 14:36
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