Author Topic: Canon 7D: Makernote metadata partialy missing  (Read 3722 times)

BogdanH

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Canon 7D: Makernote metadata partialy missing
« on: June 29, 2010, 01:08:23 PM »
Hi Phil,

I have two jpg files (exif files of both attached), both created with the same EOS 7D camera and using the same lens and (as far I could see, firmware wasn't changed between those shots). Photographer claims they are straight from camera and so far I believe that.
Main difference is, on Shot1 all focus points were used (called "Multi-point AF" in Exiftool, I believe) where on Shot2, "Single-point AF" was used.
Before continuing: use Shot2 as OK example -for comparison (because on this file, Exiftool does it's job as expected).

Now the issue... when Exiftool (tried on v 8.21 and 8.23) shows Makernote section of Shot1, not all data is shown. For example, it seems as whole 0x000d section (CanonCameraInfo7D) wouldn't exist at all. I used Exiftool to dump metadata to html (great feature, by the way) and compared Shot1.html and Shot2.htm. There I could see, that (for Shot1) section 0x000d is actually missing.
It's similar with CanonCameraSetting group: in (OK) Shot2, LensType tag (index 22) is populated according to lens being used. But in Shot1, this tag has Unknown(-1) value -even the same lens was used on both.
And what also surprised me: in Shot1, ExifIFD:ExposureProgram tag is missing (it exist in Shot2, though). Btw. I loaded "weird" Shot1 into Canon DPP and even many Makernote tags seems to be missing, DPP didn't complain.
I know, that some data (I know which) from Makernote is stripped out, if jpg file is processed with DPP -but this doesn't seems to be the case.

Do you have any idea what's going on? Btw. for Shot1 photographer complains it is not properly focused (I can confirm that) and wonders about reasons... I've tried to "check" after metadata (for "odd" values) and then I discovered above described.

Thanks for checking in,
Bogdan

Phil Harvey

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Re: Canon 7D: Makernote metadata partialy missing
« Reply #1 on: June 29, 2010, 01:34:24 PM »
Hi Bogdan,

I'm still wondering if these images were touched by some software.

How did you generate the EXIF files?  I would like to see the original structure which is lost if the EXIF was copied as individual tags. ie)

exiftool SRC -o DST.exif
or
exiftool -tagsfromfile SRC DST.exif

But the original structure may be preserved if the source is a JPEG image by copying the EXIF as a block:

exiftool SRC -o DST.exif -exif
or
exiftool -tagsfromfile SRC -exif DST.exif

- Phil
...where DIR is the name of a directory/folder containing the images.  On Mac/Linux, use single quotes (') instead of double quotes (") around arguments containing a dollar sign ($).

BogdanH

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Re: Canon 7D: Makernote metadata partialy missing
« Reply #2 on: June 29, 2010, 02:11:55 PM »
Hi,

I used "-o" (only) option, without thinking further...

Here are new files (this time "-tagsfromfile SRC -exif DST.exif" is used). Thank you for taking time.

Bogdan

Phil Harvey

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Re: Canon 7D: Makernote metadata partialy missing
« Reply #3 on: June 29, 2010, 02:18:39 PM »
Hi Bogdan,

Thanks.  Yes, Shot1 was definitely edited by some other software, and is not straight out of the camera.  In the -htmlDump output of any 7D image straight from the camera you will see unused (brown) blocks of data, but these have been removed from the Shot1 metadata.

- Phil
...where DIR is the name of a directory/folder containing the images.  On Mac/Linux, use single quotes (') instead of double quotes (") around arguments containing a dollar sign ($).

BogdanH

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Re: Canon 7D: Makernote metadata partialy missing
« Reply #4 on: June 29, 2010, 03:03:27 PM »
Thank you very much.
Inbetween I also came to this conclusion (but without being able to prove that). What bothered me was the fact, that I've expected to see at least IFD0:Software tag populated, if image was edited by some "known" software... DPP does modify/delete parts of Makernote section the way seen in Shot1 -but it writes it's signature in "Software" tag.

Have a nice day,
Bogdan