Pages: [1]   Go Down

Author Topic: Technical curiosity  (Read 646 times)

PeterAit

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 4559
    • Peter Aitken Photographs
Technical curiosity
« on: September 11, 2018, 11:43:33 am »

I am hoping one of you can explain this to me. I was scanning a legal document and the resulting scanned image had the word VOID all over it. But the document itself did not, even when holding it up to a bright light. I am curious as to how a document can be created that has this sort of hidden text that comes out only in scans.
Logged

Ivophoto

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 1103
Technical curiosity
« Reply #1 on: September 11, 2018, 11:53:06 am »

I am hoping one of you can explain this to me. I was scanning a legal document and the resulting scanned image had the word VOID all over it. But the document itself did not, even when holding it up to a bright light. I am curious as to how a document can be created that has this sort of hidden text that comes out only in scans.

Is this what you have?

http://www.highsecuritypaper.com/security-paper-information.html
Logged

Bart_van_der_Wolf

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 8913
Re: Technical curiosity
« Reply #2 on: September 11, 2018, 12:32:07 pm »

I am hoping one of you can explain this to me. I was scanning a legal document and the resulting scanned image had the word VOID all over it. But the document itself did not, even when holding it up to a bright light. I am curious as to how a document can be created that has this sort of hidden text that comes out only in scans.

Hi Peter,

Try scanning it with a higher resolution. These patterns are usually created by aliasing artifacts between the printed raster and the sensor pixels.

Cheers,
Bart
Logged
== If you do what you did, you'll get what you got. ==

Robert Roaldi

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 4763
    • Robert's Photos
Re: Technical curiosity
« Reply #3 on: September 12, 2018, 03:12:44 pm »

I had never heard of this, but doesn't it seem like something that could be part of a good plot twist in a legal thriller?
Logged
--
Robert

Patricia Sheley

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 1112
Re: Technical curiosity
« Reply #4 on: September 12, 2018, 06:37:31 pm »

Every commercial check I scanned in for the last 6-10 years had the same security built in.
Logged
A common woman~

Jeremy Roussak

  • Administrator
  • Sr. Member
  • *****
  • Offline Offline
  • Posts: 8961
    • site
Re: Technical curiosity
« Reply #5 on: September 13, 2018, 03:33:49 am »

Every commercial check I scanned in for the last 6-10 years had the same security built in.

It will be interesting to see how the latest system for paying in cheques in the UK copes with that. The idea is, using your bank's phone app, you photograph the cheque. That's then it: it's paid in. No going to the bank, no queuing to use the ATM, no queuing at the window.

I can't wait.

Jeremy
Logged

FabienP

  • Full Member
  • ***
  • Offline Offline
  • Posts: 192
Re: Technical curiosity
« Reply #6 on: September 13, 2018, 02:37:34 pm »

It is possible that only scanners (and copiers) are affected by this. Try photographing this document with a camera and see if the pattern is still visible.

I had a similar pattern on a Japanese Language Proficency Test certificate with the word "copy" and oddly enough, it would not appear on a photo of the document (due to the bayer matrix?).

Cheers,

Fabien
Logged
Pages: [1]   Go Up