Interesting! Not a folly of any sort. You certainly confirm the therory that
a +1.5 diopter should focus at 1/1.5m or 26.4"---close enough. The FL of lens
behind the diopter will not affect the working distance but only mag--all will
focus at 26." if set at infinity. I have never read that that was from the
front of the CU lens but makes sense. The diopters were designed for max FL of
200mm and I have never read anywhere if sensor size or Effective FL based on
FOV makes any difference. Have to think about that.
JS has stated that on a 300mm lens (FF) he would not risk a diopter over
+1.0---never have seen a high quality one of that strength easily available. I
am thus not overly surprised that the +1..5 Nikon out performed the +2.0
Canyon at 400mm--might be worth a quick check at shorter FL. The lens already
gets to an impressive 0.25mag natively and thus must be over 0.8 with the
diopter at 400mm. I also still wonder how the IQ with all the extension would
behave but would not get anywhere close to that mag at that FL but could try at
shorter FL--might be better IQ for largish B'flys.
Another question is how much does the diopter throw off the optimization for
the IS? (not that anything can be done but would be applicable to a MF lenses)
Paying close attention, Mike
--
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