"35mm equiv." EXIF showing wrong.

taveren · December 11th, 2005, 08:14 AM

I see this has been brought up before, but I would like to further the discussion in a new thread. Currently, a few users of my site have purchased new cameras, and within the EXIF displayed on the site, they have something like:

"Focal length: 72.0mm (35mm equivalent: 1814mm)"

Now, that's obviously wrong, but I can't figure out where it's coming from. I understand photopost isn't going to be creating this number, but the real problem stems from the fact that "1814" doesn't exist in the EXIF anywhere. Is it possible that jhead itself is getting confused about these numbers and making them up?

In relation, my own photos out of a DSLR actually have a field labeled "Focal Length in 35mm film", but it doesn't get displayed at all in the EXIF within photopost, but neither does this made up number.

Any ideas as to how I can solve this?

EDIT:

Alright, so I should have done this first. jhead reports the exact same incorrect info on the command line, so that's obviously where it's coming from. I've just installed the latest version available to me (2.4) and it reports the same thing. I'll head over to jhead for support, but are there any ideas here?

Chuck S · December 11th, 2005, 08:51 AM

Sorry nope you would need to see what jhead says.

taveren · December 11th, 2005, 09:49 AM

Well, a quick "man jhead" reveals this tidbit:

Quote:

Some CANON digital SLR cameras fail to adjust the effective sensor resolution when shooting at less than full resolution, causing jhead to incorrectly miscalculate the sensor width and 35mm equivalent focal length. Jhead usually gets blamed for this bug, but it is in fact a camera bug, and jhead can't do much about it, and I'm not about to add camera bug specific hacks to it.

Guess I need to call Canon.

Chuck S · December 11th, 2005, 09:54 AM

I admire him actually for taking a stand and saying he is not going to code camera bugs into his program

taveren · December 14th, 2005, 10:29 PM

I found that Panasonic camera's don't quite work out well either. I emailed the author of jhead and he suggested I edit the code, so I did.

exif.c: Comment out lines 856 and 861, then recompile jhead. (type 'make' and see what happens).

Of course, you won't get any support from the jhead author, nor me, so your on your own. Once you have a new jhead binary, just put it someplace (don't overwrite your old one), and change the path in the admin for Photopost.

Chuck S · December 15th, 2005, 10:33 AM

At least he told you thats good