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I'm shooting on a Canon EOS 5D.

The images that come off the camera have some EXIF data (viewable in Irfanview), such as Camera Serial Number, Firmware Version, File Number, and Camera Temperature.

When they are processed with Adobe Photoshop CS5 (not tested any other version of Photoshop), some of the EXIF data is lost.

Even a simple open, resize, Save As... > JPEG causes this behavior.

Much of the EXIF is retained (about 50%), but certain fields, including those listed above, are always discarded.

This happens whether shooting in JPEG or RAW mode. What gives? And why only some fields?

Quality: Fine (for JPEG mode) and Quality: RAW (for RAWs) is also lost.

Some fields, such as Make, Model, and DateTime for example, are preserved.

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2 Answers 2

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EXIF is a standard that programs such as Photoshop support. Within the standard is a reservation for 'Maker Notes' or custom EXIF fields that camera manufacturers use for a variety of reasons (such as shutter count in Canon 1D series). Many of these Maker Notes are used by the camera manufacturer for internal purposes, and while exposed within the image, are not really intended to provide any externally useful data.

Some online communities and the occasional program, such as Infraview, have deciphered (or think they have) some of these Maker Notes, and will reveal them. However, since they are not part of the standard, they can be changed at any time by the camera manufacturer, without warning. And of course, they could be entirely wrong.

I suspect Photoshop supports the EXIF standard, but does not expose the Maker Notes. The EXIF isn't missing, it just is not exposed in PS interfaces. Its possible that PS does not write into these Maker Note "slots" and the effect is 'lost' data.

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    \$\begingroup\$ "not really intended to provide any externally useful data." If this was true it would not be included! \$\endgroup\$
    – Darwin
    Aug 22, 2012 at 10:48
  • \$\begingroup\$ Well, it is 'Maker Notes', where "maker" is the camera manufacturer. So having space for metadata meant to be used by the camera makes complete sense, and would not be externally useful. Perhaps data that informs the JPEG conversion, who knows. \$\endgroup\$
    – cmason
    Aug 22, 2012 at 14:02
  • \$\begingroup\$ Usually the programs shipped with the Camera can make use of it. There is lots of relevant data in them. I for example use my Cameras serial number (found in the maker notes) to identify what to make backups of. \$\endgroup\$
    – Darwin
    Aug 23, 2012 at 9:02
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You should really only loose data if you "save for web" for jpeg. Although I don't do jpeg conversion in CS5 I don't think it drops the exif data.

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