EXIF has TMI - Canon EOS 400D / Digital Rebel XTi and Focus Distance

[Philnick]

Imaging Resources' sample 60D RAW files were from a beta camera, but DPReview.com has just posted a full review of Canon's EOS 60D based on a production model.

I downloaded one of the sample RAW files from that review. Examining its metadata dumped to a text file by ExifTool and Bogdan's GUI front-end, I determined that as of firmware version 2.8.1, the 60D still is not writing any tags that contain either the words focus or distance!

That makes the 400D's "focus distance swap" bug seem a mere trifle.  I can't afford a new camera right now, but even if I could, I'd wait until Canon fixes this issue!

[BogdanH]

Hi,

I'm quite sure, that 60D does write focus distance (if lens in use reports that value) -we just don't know, where that data is written.

Bogdan

[Philnick]

You're right. I just opened up one of the 60D RAW files at DPreview in DPP and it set the position of the Shooting Distance slider on the lens correction panel, and then I used Adobe's DNG converter to make that RAW file understandable to Adobe CS4, which reports a Subject Distance (in Bridge) of 5.4 meters.

So when I can afford one, I'll get a 60D - but I'm amazed that this is the case without any tags that explicitly reference focus or distance!

Not knowing enough to know what I'd be looking at if I compared the 400D's files to other EOS files in a hex editor, I'm stumped.

[Philnick]

In the meantime, now that I've massaged my XTi files so that CS4 can see the Subject Distance in them, I'll go back to using CS4 for its images, and I'll use PTLens for lens correction.

This has been a very educational and productive few days, between getting focus distance working in CS4 and discovering and changing Adobe's unforgivable default setting for Adobe Camera Raw in CS4 to downsample color information to 8-bits from 12-bits per color - not to mention getting to work with some good guys here!

By the way, I did post SwapFD.bat over in the 400D / XTi thread at the development forum for CHDK, along with instructions and a link to the home page here (to get ExifTool) about 12 hours ago. There have been two downloads of SwapFD.bat so far. No feedback yet, but that's a process that can take many hours to run.

I also posted a request to the programmers there to include a fix for the XTi's focus distance swap bug in a new version of the CHDK hack for the XTi.

[Phil Harvey]

Hi Phil,

You may be disheartened to learn that decoding maker note information is not an exact science.  Currently, only a very small fraction of the information in the maker notes is actually being decoded by ExifTool, and much of this has been done by educated guess.  The 60D may store the focus distance information, but I just checked again and it isn't in the same location as the 50D, so it may take some time before the location of this information is discovered (if at all).

Also, I wouldn't call it a bug that the focus distance tags are swapped for the 400D.  This focus distance information is in a binary data block which changes from model to model (and even between firmware versions for the same model), and Canon is free to move information wherever they want since it is (unfortunately) totally undocumented and proprietary.

If you buy a 60D and are willing to run some tests, then I am sure we can discover how to decode this information if it exists.

- Phil

Edit: Fixed typo ("bug" is spelt with a "g")

[Philnick]

Unfortunately, my getting a 60D is in the "someday" category.

"So the Biltmore garage is the spot - but the one thousand bucks we ain't got!"
- "The Oldest Established [Permanent Floating Crap Game in New York]," Guys and Dolls

When it happens, you'll be among the first to know!

PhilToo

[Phil Harvey]

Good news:  I just remembered that Imaging-Resource.com shoots flash range tests at various distances.  I downloaded the flash range series for the 60D and have now decoded the focus distance information for this model.

This update will appear in the next release.

- Phil

[Philnick]

Great!

"- but we ain't got a grand on hand!"

"And things being how they are, the back of the police station is out!"

"If the size of your bundle you'd like to increase, he'll arrange that you go broke in quiet and peace"

op. cit.