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Image-ExifTool
Posted on 2008-04-15 19:56:07-07 by mixx
Where are my millimeters gone?
Good evening,

it is not a big deal, but I am curious. I messed up the metadata of some 600 images with Lightroom, or so it seems. The tag FocalLengthIn35mmFormat got somehow changed and it does not display the units (mm) in exiftool. But otherwise the numerical value is correct. Other EXIF tools show the correct value, too, but they also show the units (mm).

As I said, not a big deal, I am just curious what happened. One can set the value, but only with a number, e.g. =36, not with a string ="36 mm".

Cheers, Mixx

Direct Responses: 7683 | Write a response
Posted on 2008-04-16 11:51:34-07 by exiftool in response to 7677
Re: Where are my millimeters gone?
Hi Mixx,

Thanks for pointing this out. I have neglected to add "mm" to XMP:FocalLengthIn35mmFormat, although I was adding it to EXIF:FocalLengthIn35mmFormat. I will fix this in the next release.

- Phil
Direct Responses: 7684 | Write a response
Posted on 2008-04-16 15:08:59-07 by mixx in response to 7683
Re: Where are my millimeters gone?
Hi Phil,

thanks but could you please briefly comment on how this works. Both FocalLength tags were exifIFD tags before I touched them. In Lightroom I changed *other* tags and saved the changed metadata back to the image. Now both of them are XMP-exif tags.

I do not mean, how LR works. I am just curious how this is handled in general (i.e. by other apps). Why are the tags classes changed?

Thanxx, Mixx
Direct Responses: 7685 | Write a response
Posted on 2008-04-16 15:35:10-07 by exiftool in response to 7684
Re: Where are my millimeters gone?
In general, newer Adobe products prefer to write XMP. Don't ask me why. Other utilities tend to leave the information as EXIF. You may find that both EXIF and XMP versions of the tag exist after writing with LR. Use -a -G1 to see if this is the case.

I don't have LR myself, so I can't test it here. - Phil
Direct Responses: 7688 | Write a response
Posted on 2008-04-16 18:56:45-07 by mixx in response to 7685
Re: Where are my millimeters gone?
Yep, that's exactly the case, both EXIF and XMP versions exist (and the mm is missing only on XMP:FocalLengthIn35mmFormat).

You know what's funny: Lightroom can not display the FocalLengthIn35mmFormat (or do they call it FocalLengthIn35mmFilm?) at all, it has a bug!

Thanks, mate! Mixx
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