Corrupted CR2 RAW file metadata?

[weixing]

Hi,
    Today, while trying the search bar function, I saw the ISO value of one of my CR2 RAW file is "ISO 6400, 6400". I check the other images I took at the same time and all indicate "ISO 6400". I open the file in Canon DPP software and saw the ISO value become "Auto". I open the original (I got backup of all the CR2 RAW files that I use in the IMatch while trying out the software) CR2 RAW file, it indicate ISO 6400 and not "Auto". See the attachment screenshot.

    I enabled the "Embed XMP in file" for my CR2 RAW file, so that the rating I set in the IMatch can be written to the RAW file as I don't want too create so many xmp sidecar file just to store my rating... may be that's a bad idea...  Just wonder how reliable is the write back process?? Also, what happen if IMatch is doing some background processing while I close the IMatch? Will IMatch warn me??

    By the way, is there a recommended settings for IMatch that will work out of the box and reliably for those new user like me??

    Thanks and have a nice day.


[attachment deleted by admin]

[Mario]

IMatch uses the well-renowned ExifTool to read and write data. This software is used by millions of users every day.
IMatch never updates ISO values in files, unless you explicitly change the ISO value in the Metadata Panel, by directly accessing the XMP or EXIF tag. Which is of course not recommended.

If your Canon software shows Auto, it may do that because it does not look at the EXIF ISO value, but another (maker note) tag that carries information about the ISO setting used at the time. Canon and Nikon are known for not always filling in the official EXIF data, but instead hiding important information somewhere in their proprietary maker notes. If you look a the metadata of your files in the Metadata Panel in Browser mode, you may find the tag which tells you the 'real' ISO setting, somewhere among the many maker notes Canon cameras write. I don't know which one, because this may change with the camera model, firmware and maybe even the phase of the moon.

[weixing]

IMatch uses the well-renowned ExifTool to read and write data. This software is used by millions of users every day.
IMatch never updates ISO values in files, unless you explicitly change the ISO value in the Metadata Panel, by directly accessing the XMP or EXIF tag. Which is of course not recommended.

If your Canon software shows Auto, it may do that because it does not look at the EXIF ISO value, but another (maker note) tag that carries information about the ISO setting used at the time. Canon and Nikon are known for not always filling in the official EXIF data, but instead hiding important information somewhere in their proprietary maker notes. If you look a the metadata of your files in the Metadata Panel in Browser mode, you may find the tag which tells you the 'real' ISO setting, somewhere among the many maker notes Canon cameras write. I don't know which one, because this may change with the camera model, firmware and maybe even the phase of the moon.

Hi,
    What I mean is I got 2 copy of that CR2 RAW file... 1 copy is use for trying out IMatch and the other copy is backup (another drive not manage by IMatch). Canon DPP software show the copy that I use for IMatch has an ISO value of "Auto", while the original copy that I store for backup has an ISO value of "6400". Actually, I now realized that the exposure compensation is also different... the copy that IMatch manage show "+4" while the original copy show "+1 1/3". See the attachment. The left is the original image and the right is the copy manage by IMatch.

   May be it's not a good idea to enable write back to the RAW file. By the way, if I use xmp sidecar file instead and I accidentally delete the xmp sidecar file, will IMatch automatically create a new one?

   Thanks and have a nice day.


[attachment deleted by admin]

[Mario]

1. Write-back for RAW files should be enabled in order to allow IMatch to keep XMP and EXIF in synch.
2. IMatch does not touch ISO or exposure compensation values.
3. I suggest you check the metadata in the file out with the ExifTool Command Processor so see what's actually in the file.
4. Does the Canon software look a EXIF metadata? XMP data? Maker Notes?
5. When you look in IMatch, do you look at EXIF data? XMP data? Maker Notes?

Just make sure you are not comparing apples with oranges.

[weixing]

Hi,

1. Write-back for RAW files should be enabled in order to allow IMatch to keep XMP and EXIF in synch.
2. IMatch does not touch ISO or exposure compensation values.
3. I suggest you check the metadata in the file out with the ExifTool Command Processor so see what's actually in the file.
4. Does the Canon software look a EXIF metadata? XMP data? Maker Notes?
5. When you look in IMatch, do you look at EXIF data? XMP data? Maker Notes?

Just make sure you are not comparing apples with oranges.

I copy both files to the same folders and run the ExifTool Command Processor to list the Metadata and below is some of the related tag (See the attachment for part of the screenshot):
Original Copy
[ExifIFD]       ISO                             : 6400
[ExifIFD]       Exposure Compensation           : +4/3
[Canon]         Camera ISO                      : Auto
[Canon]         Base ISO                        : 6400
[Canon]         Exposure Compensation           : +4/3

IMatch Copy
[ExifIFD]       ISO                             : 6400, 6400
[ExifIFD]       Exposure Compensation           : +4
[Canon]         Camera ISO                      : Auto
[Canon]         Base ISO                        : 6400
[Canon]         Exposure Compensation           : +4/3

    After I import to IMatch, I did run the GeoSetter to set the GPS data in the RAW files, but didn't notices anything odd. Anyway, this is just a test set and I'll be more careful when I start doing the actual import once I plan out my new workflow... will add some error checking in my workflow.

    By the way, when you mention "Write-back for RAW files should be enabled in order to allow IMatch to keep XMP and EXIF in synch.", you mean write back to RAW file directly and not the xmp sidecar file, right?? I remember the default for Canon CR2 and CRW is to write to xmp sidecar file, right?

    Thanks and have a nice day.



[attachment deleted by admin]

[Mario]

Most applications use sidecar files to contain the XMP metadata for RAW files. This is also the default in IMatch 5.
Legacy IPTC/EXIF data can only be stored in the image itself.
In order to keep the EXIF / IPTC stored in the image file in synch with the XMP data in the sidecar file, IMatch must be allowed to update existing EXIF/IPTC in the image file. IMatch by default does this, but does not create EXIF/IPTC - as per recommendation of the Metadata Working Group.

As said IMatch does not update ISO or shutter speed values. But you said you used GeoSetter as well on these files. Maybe GeoSetter introduced the changes? If this is not the case, please explain me in detail what you do with these files in IMatch in order to change the ISO or other values.

[weixing]

Hi,

As said IMatch does not update ISO or shutter speed values. But you said you used GeoSetter as well on these files. Maybe GeoSetter introduced the changes? If this is not the case, please explain me in detail what you do with these files in IMatch in order to change the ISO or other values.

That's the problem... I had no idea... if I know, it won't be an issue anymore... I only notice the issue and try to find out what might cause it, so that I don't make the same mistake when I start importing all my images to IMatch. Anyway, I'll design my workflow to include some error checking before import into IMatch... will update if I found anything.

    Thanks and have a nice weekend ahead.