I was just checking EXIF data on some shots, and notice that none of the RAW files have the distance to subject filled in. I've checked using CaptureNX, Adobe Bridge CS6, and PhotoMe. I also had shots taken with both a Sigma and Nikkor lens.
I could've sworn that I've referenced this data before, but it was quite some time ago.
>I see the distance data using PhotoME. > >It’s listed as unknown in the Camera section, but it is >reported in the Manufacture’s Notes under the Lens Data >section; although I don’t know how accurate that reported >distance is. > >Pete >
Well, yep, there it is. I could swear that wasn't there yesterday using PhotoMe.
>Point taken on accuracy. I was looking for accuracy of +/- 1 >foot at 30 feet or so.
This isn’t authoritative but base upon my experience but I think the distance is fairly accurate at close focus distances and depending on the lens gets less accurate with increased distances.
As to depending on the lens, for example my Nikkor 17-55 f/2.8 from near focus to about 5 feet uses about 2/3 the amount of travel of the focus ring. The next distance reported after 5 feet is 10 feet then to infinity in the last 1/3 travel. I have not checked it thoroughly, but I imagine the reported distance will be fairly accurate in this case up to about 5 feet, than the accuracy getting exponentially worse after 10 feet (small amounts of movement create greater amounts of focus distance change).
My understanding of the distance info is that it is for use in the flash metering. In that case, close distances would be fairly accurate but longer ones not so much since that lower level of accuracy is all the flash system needs.
---------+---------+---------+---------+ Joseph K Seattle, WA, USA
Sat 01-Dec-12 01:59 PM | edited Sat 01-Dec-12 02:04 PM by Chris Platt
30ft with a 400mm lens should get you accuracy within that 1 foot range. My tests suggest that the reported distance for fairly close objects is quite accurate. 30 ft at 400 mm is very close. I just tried it with a 400mm setting, measuring a 29' 9" distance from the focal plane to a target with a tape measure. I tested with aperture settings from f5.6 to f32 giving DOFs that ranged from about 1/3 foot to 2 feet. I then tested at 100mm from f5 to f25 giving a DOF range from 3 feet to 35 feet. In every shot the exif reported 29 feet. If your target is beyond the hyperfocal distance the focus distance reported won't be the camera to subject distance, but probably something very close to the hyper focal distance (the near limit of the infinite DOF).