Copyrights to photos is a complex subject so if you're able to come to sort of 'limited use with attribution' agreement with website-owner, that's always preferable to copyright wrangling.
A good overview in the UK is at
https://www.gov.uk/guidance/ownership-of-copyright-works. The first answer to any questions about photo copyrights is usually "it depends".
In general, Malky's right. The photographer (or his/her employers) normally hold copyrights to the
content of the original photo. One or more prints/copies of these might have been made over time but these don't affect the copyright. So the website owner is unlikely to be able to claim copyright of a 'photo found in the attic'.
Two possible exceptions are:
- The website's owner's ancestor in the WW1 photo was also the photographer (or owned the camera) or purchased the copyright.
- The website's owner's ancestor commissioned the photographer to take the photo. In that case the copyright would lie with the person or organisation that commissioned the photo.
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So normally, copyrights would pass to descendants of the
photographer, not to those of people in the photo. The photo may (legally) still be copyrighted somewhere by someone but unless the photographer is known and copyright holders can be traced, then the copyrights are 'orphaned'.
The number of years copyrights may exist are in the PDF for published and non-published photos. I doubt whether the website counts as "publication" since no permission was given by a copyright-holder. As the PDF says, it is unlikely that a 'retouched/restored' version of the original can be claimed as a 'copyrighted' new work.
A separate issue is - if you were to copy the photo from the website - the website owner could claim you were copying part of his/her website design or content. He/she does hold copyrights to the website as a whole (design, text, etc.). I've idea how the photo copyright fits into this.
Bottom line: try and come to an accommodation for limited use with attribution.
Mike
PS.
https://www.legalgenealogist.com/2012/03/06/copyright-and-the-old-family-photo/gives a good overview (based on US law).
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It's not my photograph. It's an image I have seen online from WW1 where the website owner is claiming copyright because they have a copy of the photo (either inherited, purchased or sent to them by someone else) and have uploaded it to their website.