Can you trust your meta data?
May 27, 2010 13 CommentsWe all talk about tags, and flags and meta data whenever we are importing our photos into Photoshop, Lightroom, Aperture, or whatever program you use. While there are discussions ad infinitum about the value of adding extra tags to your photos like “2010″ or “Canon” or “family vacation” or whatever labels you like, there is an underlying set of “fixed” data that contains HUGE amounts of information about your picture, and that is the EXIF data.
EXIF data refers to the data the camera records about the scene you are capturing, including things like shutter speed, aperture, camera body, date, time, and all that sundry stuff. While this may seem like useful information to have (and it is at times), it can often be misleading. To prove this point I did a little test shot with the trusty rusty 40D in hopes that it would help illustrate the perils of relying on the EXIF data…(yeah, I knew the outcome ahead of time, but humor me here!)
For this exercise, because no models were handy around midnight, you’re gonna have to deal with yours truly here. I captured an image and recorded several settings, and want to show you which ones were correct and incorrect in camera. So, here’s the image I captured.:
While the camera reliably recorded things like shutter, aperture, ISO and all that jazz, take a look at the native EXIF data here, and tell me what you think is missing from the shot (I’ll share the answer tomorrow). To leave you with a hint, it’s something pretty obvious that is missing from the EXIF, so don’t try to read between the lines too much. If you look at the shot, and the EXIF that was reported, it hopefully will jump right out at you.
Fair warning too, because I will be using this shot to talk about a few aspects of portrait photography coming up next week…but the biggie is coming tomorrow, so tell me what you think is missing and we’ll see who gets it right. In the meantime, go read another blog so you can stop looking at the smirky face above! Happy shooting! 
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Hello and welcome to Canon Blogger. So, what is this place really all about? So glad you asked! Canon Blogger is all about sharing. Sharing insights and experience from a photographer, blogger, an IT Professional for nearly ten years now, and most importantly, an educator! My name is Jason Anderson and I am the host of CB. I have been working with photography in various capacities for about seven years now.
Well, Jason, it certainly looks to me like you have a flash hitting your face, contrary to what the EXIF says. If so, was it a Canon flash? I don’t know/remember what flash(es) you’ve got…
An astute observation Michael…
I’m guessing this was the right answer.
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Your focal length.
Interesting…the lens is reporting as a Canon 50mm, but the focal length is 70mm – how could that be?!?!
Would that be due to the 50D’s crop factor?
You mean the 40D? (I shoot with a 40D, so that part is right)…
I think it’s because the lens I was using is somehow not reporting right in Photoshop Database…
Hmmm, I think it is actually the aperture value. It says the lens is EF50mm f/2.5 Macro; however, the maximum aperture is reporting only f/2.8.
Another astute observation about the discrepancies in EXIF – so much for reliability, eh? So, which is the most obvious from looking at the shot and comparing it to the EXIF?
To me what seems most obvious is that a flash fired, but does not reflect this in the EXIF. Can see the catch-lights in the eyes.
That’s two guesses that it’s the Flash …(that was my first observation too…basically a “Huh? but it did fire!” on my part!) I’ll have details tomorrow…
My Canon 5D MK II EXIF always shows ‘no flash’ even when I use one. I normally use a Pocket Wizard to control one or more Canon 580 EX II flashes, but I don’t think I have a single EXIF that reflects that any flash was ever used.
At any rate, when I saw the EXIF, things I saw were the lack of flash and the erroneous focal length — or at least I didn’t think LR would report a crop factor rather than actual…