vss4canon wrote in post #16746832
It's hard to respond to your post without knowing exactly how this this EXIF information is determined. My point in regard to "range finding" involves using rotational gear position in relation to the know characteristics of any given lens to determine "focus distance". The rotational position of the ultra sonic motors (USM) gears which drive these lens barrels through their focus, together with a first or second order equation should allow one to calculate the focus distance which can in turn be used with the other know variables (f-stop and focal length) to determine "near" and "far" focus limits.
It's hard to respond to your post without knowing exactly how this this EXIF information is determined. My point in regard to "range finding" involves using rotational gear position in relation to the know characteristics of any given lens to determine "focus distance". The rotational position of the ultra sonic motors (USM) gears which drive these lens barrels through their focus, together with a first or second order equation should allow one to calculate the focus distance which can in turn be used with the other know variables (f-stop and focal length) to determine "near" and "far" focus limits.
The steps I followed:
- Take a photo at each measured distance (1' intervals for the Excel table data).
- Copy photos to harddrive
- Drag and drop each photo to EXIF viewer
- Read & record the distance field value within the EXIF data of each photo.
I used two different EXIF viewers, in case one program had a bug in distance values. Canon 17-55mm lens was used for the Excel data. Canon 70-200 f/4L IS was used in the link.
Using a Canon 70-200mm f/4 LIS, distances reported took big jumps, as detailed in the link. At about 190' and farther, the EXIF reported a very huge number that one can only interpret to be 'Infinite'.
Now are you convinced of the sound, scientific method I used to confirm how messed up Canon distance reporting in photo EXIFs really is?!
