Interpreting EXIF

[David Stephens]

I took an image of a Northern Harrier hunting from maybe 100 to 150 yards. The setup was a Canon 7D with an EF 400mm f5.6L. The EXIF says "Subject Distance: 655.16m" which I interpret as 655 meters. Using DPP to look at the focus point, it's on the bird. The line of trees beyond the bird might be another 100-yards at most. Is the cropped-sensor somehow messing up the distance to subject reading, or is something else going on?

Thanks,

Dave

[Roger Clark]

David,
As the subject distance gets greater, the error in determining the subject distance increases. The camera may have an error in the infinity point (which may be independent of actual infinity focus). For many bodies, Canon disabled the distance indicator due to this inaccuracy. You could try some calibration points. For example go to a football stadium and image the goal post from known distances and compare to what the camera says. Then image something at infinity, like the moon and see what it says.

Roger