GeorgeL
**Member** 
Posts: 5
What I collect: Canada 1942 War Issue, PEI RPO's, Canada WWI, Early UK Revenues
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Post by GeorgeL on Jun 30, 2023 13:56:29 GMT
I have covers with similar postmarks which I know have multiple hammers used. I am trying to determine the hammer #, but I am having difficulty.
I was wondering:
1) Which programs are you using to overlay a translucent image of one over the other to see the differences? How are you keeping the images true to the real size of the postmark when scanned?
2) Is there a program that is an overlay gauge, that when placed over the postmark can give exact distance from point to point, and angles?
Thanks in advance,
George L
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stainlessb
Member 
qaStaHvIS yIn 'ej chep
Posts: 4,644
What I collect: currently focused on most of western Europe, much of which is spent on France, Belgium, Germany and Great Britain Queen Victoria
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Post by stainlessb on Jun 30, 2023 14:41:52 GMT
George
I do not know of a program specifically for overlays, but Adobe Illustrator or Gimp both allow you to adjust the opacity of an image , which would allow you to place over another image. The size would all be on having identical scanner settings (crop dimension) AND havind each item scanned 'square" to the scanner table as adjusting skew to straighten something out has a clight affect on the image size.
Illustrator may be a bit easier to use, but it is a bit $$, Gimp OTOH can be downloaded for free with no limitations.
I don't believe either program allows one to directly 'measure" but there is probably a work-around for that.. There are programs that provide precise meassurement on images, but I can't remember the names as I do not have any on my computer.
A passed member (user name WERT) was very good with these types of programs- it might be worth searchingthe forum for his messages.
Good luck and keep us posted!
Cheers
Stan
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Ryan
Member
Calgary, Alberta, Canada
Posts: 2,721 
What I collect: If I have a catalogue for it, I collect it. And I have many catalogues ....
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Post by Ryan on Jul 1, 2023 2:16:40 GMT
How are you keeping the images true to the real size of the postmark when scanned? One thing to keep in mind here is that you can't automatically assume that your scanner is accurate. One way I've tested my scanner in the past is to scan something on both the vertical and horizontal - in my case, I used a machinist's ruler (this also allowed me to figure out how many pixels per inch or centimeter when trying to extrapolate image size from a scan). If the scanner is accurate, the pixel size of the vertical image should be just the same as the size on the horizontal image, but in my case the scanner was out by slightly over 1%, if I remember correctly. It's not a lot, but the difference between a 25mm postmark ring and a 26mm ring is only 4%, so there isn't a lot of leeway available in your measurements. Ryan |
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FDI
Member
Member of RPSC & BNAPS
Posts: 351
What I collect: Modern Canada (misperf, varieties, tagging errors), Canadian Cinderellas, EXUP & CAPEX & Dead Countries
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Post by FDI on Jul 1, 2023 14:55:04 GMT
I use this Magnifier to see and reveal some details on stamps. Very useful for re-entries, damages on stamps or reverse image for postmark clarity. Unfortunately, it does not provide any measuring tools. apps.apple.com/ca/app/magnifier/id1563316278 |
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GeorgeL
**Member**
Posts: 5
What I collect: Canada 1942 War Issue, PEI RPO's, Canada WWI, Early UK Revenues
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Post by GeorgeL on Jul 3, 2023 11:03:05 GMT
Thanks so much for the information. I picked up the Bridger and Kay cancellation gauge and a boley gauge this weekend, so I will go old school initially, and then compare it with your suggestions. One other thing I would like to learn is how to subtract a specific colour in photoshop. If I’m able to do that it should be able to enhance the cancel in difficult to see areas.
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Ryan
Member
Calgary, Alberta, Canada
Posts: 2,721
What I collect: If I have a catalogue for it, I collect it. And I have many catalogues ....
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Post by Ryan on Jul 4, 2023 5:02:44 GMT
One other thing I would like to learn is how to subtract a specific colour in photoshop. If I’m able to do that it should be able to enhance the cancel in difficult to see areas. Once upon a time there was online software known as retroReveal which allowed the user to upload an image, and then offered a number of choices based on twiddling of graphical colour values. The various altered images which were produced would often include one or more which strengthened the image of the postmark, allowing it to jump out with greater contrast when compared to the original scan. That software has since gone defunct, but two of our members here on TSF have come up with replacements meant to reproduce the functionality of retroReveal. Have a look at these two threads, they might offer you some help with enhancing cancels. Postmark-Reveal.com, a Retro-Reveal AlternativeImageSleuth - another retroReveal replacementAnd for completion's sake, here's the thread which originally introduced us to retroReveal. Revealing Lost Content - retroReveal.org SITE NOW DEFUNCTRyan |
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