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I have a series of around 100 scans of vintage stamps (all coming from the same scanner), and just a couple of actual stamps within that set, to be used as color reference. What's the best process to find a good color transformation, in order to print reproductions that are as close as possible to the references, color-wise?

I unfortunately don't have an ICC profile of the original scanner used to scan the stamps; they were scanned a couple years ago, by someone who's not in contact with the source anymore, and these stamps are almost one-of-a-kind, so sourcing them on the Internet is out of question (btw: I'm not looking to create counterfeits, just a memorabilia poster for what used to be my dad's collection).

The stamps were originally printed with a CMYK process, measured at LPI 120, on white paper. Stamps were then scanned on a RGB scanner at 600 DPI, so enough to see the halftones of the print plates. I would like to reproduce the poster on a semi-pro color laser printer (I have access to a C9000 OKI unit).

Before you say it's impossible to create a perfect match of an offset CMYK print using a laser printer: I already know! I'm just looking for a close enough match.

My current approach: I disable all color correction in the printer, then:

  1. do a test print of a scan
  2. compare it with the actual stamp I have as reference
  3. scan the print together with the reference
  4. find the color levels / curve transformation that gets the print closest to the reference
  5. apply the transformation to the scan, and iterate from point 1.

As you can guess this is incredibly time-consuming.

Is there a better approach? For instance, is there a process that I can follow step by step to iterate more quickly to a close enough match?

EDIT: clarified exactly what material I have (stamps / scans)

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    I'm a little confused about what material you have. You mention that the stamps were printed with a CMYK process. Does that mean that the scans you have are scans of the offset printed stamps and not the original stamps? And then additionally you have some original stamps as well? But you don't have the CMYK prints which were scanned?
    – Wolff
    Jun 6 '21 at 21:38
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    I think the "close enough" is very subjective, as in, how much time do you want to spend on this project ? I assume the stamp scans are a variety of colors, not sure you have an actual sample stamp of each color. You can probably speed things up a bit by determining an overall adjustment to the scans- such as they need a 20% boost in magenta- then apply that to the lot of them. Still it seems you will need to go through each scan and tweak it to your liking. The big thing is doing an adjustment to one stamp perfectly and then a laser test print to see if what you see on screen is accurate.
    – Kyle
    Jun 6 '21 at 22:23
  • @Wolff thanks for pointing this out! I've updated the description to make it clear that I have only some of the original stamps, and the RGB scans of the whole set. I pointed out that the original stamps were printed in CMYK just as extra information, what I really meant was that they were printed in color :) Jun 8 '21 at 20:33
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    You can probably get the ICC profile used by the scanner by looking at the image file's metadata in your file browser.
    – 13ruce
    Jun 8 '21 at 20:44
  • @Kyle you're correct that the scans are of a variety of colors and I only have 7 stamps total. Since the scans are coming from a single scanner, I hoped to be able to find the single good adjustment for the 7 that I have, then applying it to all images, and I would be able to print them all with reasonable confidence that even the ones without reference would be close. Jun 8 '21 at 21:04

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