EOS 10D EXIF metadata question

[rwbowman]

I'm using a Canon EOS 10D camera and Photoshop CS with the latest RAW plugin (2.3). In

Photoshop's display of Camera Data (Exif) information, the item "Lens" is shown, and

beside it the focal length of the lens used, for example, "28.0-70.0mm." Does anyone

know the correct exif property name for this item, and its correct EXIF tag? (Note, I'm not

referring to the exif items F-Stop, Aperture Value, or Max Aperture Value.)

 

Many thanks!

[mark u]

Read all about it here:

 

http://www.exif.org/Exif2-2.PDF

[rwbowman]

Mark, thanks for your response. I've read the EXIF specifications document, but I don't

believe the information I'm seeking can be found there.

[malcolmdwyer]

If you have access to perl with Image::Info installed, you can try this:

 

perl "-e" 'use Data::Dumper; use Image::Info qw(image_info); print Dumper(image_info(shift));' filename.jpg

 

(Obviously, replace 'filename.jpg' with the appropriate filename).

 

Image::Info grabs all the EXIF data out of the jpeg, and data dumper prints a list of all key:value pairs for you. You should be able to match up the value given by Photoshop with one of the keys.

 

I don't have access to such a system right now, but if no one else gives an answer, I'll try it when I get home tonight where it should work, and I'll post again. (I've got the 10D, so I should be able to give you the exact key).

 

Malcolm

[malcolmdwyer]

Well... There's no one tag in there identifying the lens... but I found these tags in a picture taken with the 17-40.

 

'Canon-ShortFocalLengthOfLensInFocalUnits' => 17,

'Canon-LongFocalLengthOfLensInFocalUnits' => 40,

 

And then there's this one identifying how big a FocalUnit is...

'Canon-FocalUnitsPerMM' => 1,

 

Hope this helps. Let me know if you want more info... I've got a script I use for my personal webpage photo gallery that extracts a bunch of these tags.

 

Malcolm

[malcolmdwyer]

And for future reference to anyone coming across this thread... drop the double quotes around the -e in the command line I gave above. It should be:

 

perl -e 'use Data::Dumper; use Image::Info qw(image_info); print Dumper(image_info(shift));' filename.jpg

 

Malcolm

[rwbowman]

Malcolm,

 

Thanks very much for your help. I've learned since my original posting that the two items

you extracted "CanonShortFocalLengthOfLensInFocalUnits" and

"CanonLongFocalLengthOfLensInFocalUnits" are "Canon MakerNote data in IFD format" a

reference to which is here:

 

http://www.burren.cx/david/canon.html

 

Unfortunately, this doesn't get me any closer to extracting the data for my use, as I'm far

from expert in understanding the world of metadata, perl, etc.

 

If there were some way you could extract the tag without going to too much trouble, I'd be

most grateful.

 

Cheers and best regards,

 

Rob

[mike_morgan1]

Look for a program called exifer