Watermark Extraction Technique

Per a request from StampStudy on this thread, here's the method I use to extract watermarks from my stamps in a completely non-destructive manner. I've yet to find a stamp from which I couldn't pull a fairly good watermark using this method. YMMV.

For this method to work, you need:

(1) a flatbed scanner capable of scanning film negatives. Most "photo" scanners have this capability, but check your documentation.

(2) photo editing software that can do color curve adjustment. The big 3 -- Photoshop, Photoshop Elements, and Paint Shop Pro X3 -- can all do curve adjustment. I recommend Photoshop or PSP X3, as both allow you to work in CMYK (Cyan, Magenta, Yellow, Black) mode as well as RGB (Red, Green, Blue). The ability to work in CMYK makes this process MUCH easier, and yields much better results. PSP X3 is the reasonably priced option at $40, versus Photoshop's $700 tag.

All examples shown here were done using an Epson Perfection V350 Photo Scanner with Epson Scan software, and Photoshop CS5.

1. The source -- the stamp used for this example is a beat-up copy of Deutsches Reich Mi 616, from the 1936 Summer Olympics set.



2. In your scanner software, set the scan mode to photo negative.



3. Here's the resulting photo negative scan.



4. If your software can do CMYK, change Mode to CMYK Color.



5. Go to Channels tab, and select the channel which best shows the watermark. The best channel will depend on the stamp color. In this case, if you look closely at the thumbnails next to the individual channels, you can see the swastika watermark in the Yellow channel. (If in RGB Mode as opposed to CMYK, your options will be Red, Green, or Blue)



This is what it looks like with just the Yellow channel selected.



6. Select the Curves adjustment.



7. Adjust the curve line to bring out the watermark. In this case, I bent the curve of the Yellow channel upward.



This is the result.



8. Invert the color to go from the negative (as scanned) to positive.



9. The end result.



I've also had decent luck using this method on postal stationery, despite the greater thickness.


Original


Negative


Positive

Cool, neat, wow, thanks.
Does the free GIMP program do this also for those of us in the cheap seats? (I haven't yet got GIMP myself, just heard it mentioned.)

PostmasterGS, that's a most instructive tutorial & I will certainly
try this.


Many thanks. Just shows again what can be learned on SCF.

I don't have firsthand experience with GIMP. My Google-fu tells me it will do curve adjustment with RGB, and there's a plugin that may allow CMYK.

PostmasterGS, I have a HP Photosmart 2610 all-in-one scanner/printer but it doesn't seem to have the scanning film negatives capability. So I understand the process correctly, does your photo negative scanner have some sort of backlight in the scanner lid?
Regards
Mike

Postmaster,

Wonderful tutorial! Thank you!

Have you tried this technique for detecting faults (like thins, pinholes, small tears, etc) and/or grills on 19th century US stamps?

Brian

Mike,

It does. Most flatbeds marketed as "photo" scanners now have this feature.

The inside of the scanner lid looks like this (same model as mine, but I've put a black background on mine instead of white):



With the inner mat of the lid removed:



The lamp doesn't cover the entire flatbed surface, so scanning larger items can be a challenge, but it works really well for your average stamp.

Brian,

I haven't used this specific technique for detecting defects, but some variation of it should work nicely. That's the beauty of being able to digitally manipulate the image -- there's always some combination of adjustments that will reveal the hidden details. Some variation would probably also work for grills, but I don't collect US, so I don't have any way to test that out.

Postmaster, thanks for taking the pictures of your scanner so I can see how it scans negatives.

Wow, most informative! I have exactly the same scanner and finally got some decent watermarks after using the negative scanner setting.

It was time consuming but I will definitely be using this method to scan images of watermarks for display.

In this process I also found out how to bring out a postmark on a white background which I will be using all the time.

Many thanks!

Postmarks are even easier, as they don't require the ability to scan in the negative.

This was done in Photoshop -- CMYK Mode, using Color Replace, Levels, and Curves adjustments.



Though admittedly, it's less effective when the stamp has dark colors on it, since it's difficult to differentiate them from the cancel.

Wow, this is amazing and I will definitely have to try it. I have one quick question, will this still work if the stamps are hinged onto thick paper? I recently bought a large collection that is all in albums and well organized as such. However, it has not been checked for watermarks and I would prefer to leave the stamps as they are for now. It would be very handy if I can simply scan the entire page as is..

I doubt it, but it might just depend on the thickness of the paper and its relative transparency.

I would love to see it tried on a single line watermark of the United States series, the Washington/Franklins.

I have an inexpensive Canon LidoScan, so I really don't know what capabilities it has along these lines. I guess an intense study of the manual is in order.

I don't have one to try it on, but if anyone can negative scan one and e-mail it to me, I can work some Photoshop magic on it.

Wow that is fascinating to say the least! I would have never ever guessed that their was swastikas used as watermarks! I think it's a very cool (and scary) idea as those who don't study history are bound to repeat it. Also thank you for the instructional/tutorial.~Jay