Hello Jochen,
I have my IQ3100 Tr. / Achromatic files checked. I could not find any value with SubjectDistance in the EXIF data. I was sure I would have seen the value at some point, but I also had different firmwares over time. I can not keep up with that.
But I also took a closer look at the EXIF data from IQ4. For this I have built a tripod and always shot the same motifs with different lenses. The focal point/Object is about ~ 4m away.
Schneider Kreuznach 35mm Br. LS F3.5Schneider Kreuznach 45mm Br. LS F3.5The lens does not write a SubjectDistance value in the EXIF data.
Schneider Kreuznach 80mm Br. LS F2.8The lens does not write a SubjectDistance value in the EXIF data.
Schneider Kreuznach 120mm Macro Br. LS F4Focus distance switch on the lens to "LIMIT".
Schneider Kreuznach 120mm Macro Br. LS F4Focus distance switch on the lens to "FULL".
Schneider Kreuznach 120mm Macro Br. LS F4Focus distance switch on the lens to "FULL".
Nonsense value - camera / lens was not moved or refocused.
Schneider Kreuznach 240mm Br. LS F4.5Mamiya/Phase One 300mm APO F4.5The lens does not write a SubjectDistance value in the EXIF data.
It is strange that the SK 45mm Br. LS - as one of the newest lenses - does not write a SubjectDistance into the EXIF data. The SK 80mm Br. LS supports AFR with the HAP-2 (Honeybee Autofocus Platform 2.0). To support AFR, I think the camera / lens must know the SubjectDistance to recalculate the autofocus when panning the frame. The SK240 says that it had 1m more distance - which is not true. The SK120 writes - from time to time - nonsense values. And look at the different notations with the thousands point.
From what I've seen, I would not rely on the SubjectDistance values in the EXIF data at IQ4.
I hope this information will help you further, I can not tell you more ...
Greeting Gerd