Whilst following the threads of "The case of the the missing COMMENT (DOpus versus. Exif Tool, round 10)" I have come across a problem with the DOpus imagedesc metadata field.
If I take the following experimental very long capthion
This is a caption and it This is a caption and it This is a caption and it This is a caption and it This is a caption and it This is a caption and it This is a caption and it This is a caption and it This is a caption and it This is a caption and it This is a caption and it This is a caption and it This is a caption and it This is a caption and it This is a caption and it This is a caption and it This is a caption and it This is a caption and it This is a caption and it This is a caption and it This is a caption and it This is a caption and it This is a caption and it This is a caption and it This is a caption and it This is a caption and it This is a caption and it This is a caption and it This is a caption and it This is a caption and it This is a caption and it This is a caption and it This is a caption and it!
And enter it into the the imagedesc field, it is truncated at 512 characters. And the Infotip of that field shows 512 characters.
If I now place this long caption in the Description Field in Photoshop and save the file the Description field it is not truncated. The Infotip shows the full number of characters. If I interrogate the imagedesc field in DOpus it also shows the full caption.
This indicates to me that something in DOpus is preventing the writing of long captions to the imagedesc field.
It is not something that happens every day, but very long captions are a definite possibility.
It doesn't really seem like a bug to me, just two different programs imposing different maximum lengths on input fields.
512 seems a reasonable maximum comment length to me, even if another program has a larger maximum.
(Especially when Opus won't display larger comments from EXIF data, which is a workaround for problems caused by the very same other program storing so much automated metadata in things that it causes major performance or memory usage problems.)
I am sorry, but I think it is a bit more serious than that. If you are a pro or semi-pro photographer earning a living by selling photographs, the one thing you have to be very, very sure of, is that Photoshop - the de rigueur image editing software worldwide - accurately reflects your metadata. Captions over 512 characters are very possible, and, from my experience not that uncommon.
This situation means that from now on I have to check the length of my captions and any over 512 characters in length I will have to add via Photoshop. Even worse, I have no idea if all the captions on thousands of images are complete, and any captions that are not, I cannot restore as the characters from 513 on have been consigned to the ether.
There's going to be a length limit whichever software you use. EXIF doesn't support unlimited length text fields. If you're worried about extremely long comments and having to check the length of things first, that applies whichever program you're using, just with different limits to check against.
(I'm assuming this has never really happened, and you only noticed it because of the other thread about length limits on this field?)
It’s only the one specific field (comments) that the limit is applied to, and it’s only applied when reading metadata, not writing it. I think you would have noticed by now if it was a real issue.
Now I’m REALLY confused. As far as I can tell, descriptions have never been truncated for me. I made a point of stating, in my own post to “The case of the the missing COMMENT”, that I routinely write the same string, long or not, to DESCRIPTION, SUBJECT, TITLE and COMMENT, and I’ve never noticed any of those getting truncated — just the COMMENT disappearing from DOpus’ view when it is 513+ characters, though the actual metadata is unchanged. Please take a look at the description for “1 DOpus\2020-12-15 23;59;59 - General - xFGHI-00001 Invoice 1234567890 - 07 (513 ch).png” in the 7-zip I attached to my post there. Does it not exhibit a 513-character string for you?
I just injected your 825-character into a dummy PNG with no metadata, and it did not get truncated for me. If you want to zip and upload an image you’ve gotten the truncation with, I’ll take it for a spin here.
Many thanks for your help with this. Now I appreciate that it is only on an Opus read that the Comment file is truncated, my problem goes away.
I copy every imagedesc field in the File's Comment field so that I can search via the windows indexer, which regards the imagedesc (Caption) field as so unimportant it will not let you search against it.
I have shown that I can put in a 800 character comment field and still have windows indexer searches succeed.
As Jon said in his reply, in the real world it is not an issue - at least for me. Apologies for bothering you.