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by w.hrybok

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I have been using an SX30 and they have a particular feature where each face has a bounding box when reviewing images taken with auto-focus set to Face Detect. There are two types of boxes: white ones, which indicate the face was being auto-focused; and gray ones, which mean a face was detected but not focused on.

My question is this: Is there some EXIF data that can tell me where the gray boxes are located in the image? I can find EXIF tags for the white boxes (based off of the AF points), but none for the faces that were not focused.

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1 Answer 1

EXIF is standards based, so info such as this that would be specific to a particular camera maker or even model would likely not be easily deciphered. Typically this kind of information is in what are known as 'maker notes" which are areas of EXIF reserved for platform specific info. Unfortunately, this info is not exposed by Canon, nor do they tell anyone what or how they use this info.

There are those that have done some work to decipher this info, but often it is camera specific and a 'best guess': Scroll down to Appendix 5 in this document:

http://park2.wakwak.com/~tsuruzoh/Computer/Digicams/exif-e.html

For Canon, I find that the Canon supplied tools often have features that detect focus points etc, such as ZoomBrowser. However, I have not seen any 'face detect' information.

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I believe Canon share some of this information with 3rd parties as well, as Apple's Aperture photo management software includes focus points for Canon DSLRs, both for regular AF points and the LiveView AF area (450D, 7D, 5DIII). I've never used face-detect focus, nor do I have a Canon point & shoot, so don't know if that comes up too or whether it would be stored in the EXIF data. –  drfrogsplat Feb 19 at 2:08

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