Many thanks - I'm going to be in New Mexico (hopefully!) for the month of January for an artist-in-residence program, so I hope to have many more opportunities for environmental portraits there (I'll be using the 907x alongside my Nikon Z7).
I'll be interested to find out how you like using the manual-focus R lens vs the native XCD lenses. I had that brief time using my 50 Summilux, but in the end I sold the lens and returned the adapter. I personally didn't see any advantage as these XCD lenses are so good, but here again that's just for my personal workflow. I do definitely appreciate the attraction of using different lenses, as I'm finding out with my vintage V lenses.
Congrats on the AIR program! I hope there are no obstacles in the way of that.
To be sure, I prefer using the 907x with XCD lenses. However, I have the adapters so that I can make use of other lenses ... Not so much because I think they're better or interesting, but because I have them and I can see from using them what might suit me better were I to buy another XCD lens.
I did some testing with the Summicron-R 90 this morning...
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I taped a color chart and a tri-tone chart to the wall, set the camera up on a tripod at 6.75 feet away, and did two sets of test exposures at all f/stop settings ... One with the lens hood collapsed and the other with the lens hood extended. I used a Fotodiox Pro Leica R to Hasselblad X mount adapter and manual exposure (metered with my old faithful Sekonic L358).
For processing, each frame was slightly different on color balance, so I used the white balance eye dropper to normalize them, picking the white tone in the tritone chart. Exposure was slightly under what I'd prefer, so I set all exposures up by +0.9EV. Also, because I used lighting through the window at the left of the target, I applied the same gradient filter to all exposures to even out their density from left to right.
First three of just snaps of the camera with the lens and adapter mounted, taken with the iPhone 11 Pro on a tripod:
907x_Summicron90-1
907x_Summicron90-2
907x_Summicron90-3
Evaluation of the frames showed no differences between the set with the hood collapsed and with the hood extended, so the following is a frame comparison across the set:
There's some corner/edge falloff at f/2 to f/4, then from f/5.6 to f/16 illumination is very even across the entire frame, and virtually indistinguishable at all four of those lens openings.
I include a full frame capture of the f/5.6 frame as being indicative of what one might expect using this lens on 33x44 format.
Summary: This is a nice adapted lens on the 907x. It performs well—even the falloff at f/2-f/4 is pleasing for some kinds of photographs. The resolution becomes sharpest at f/5.6 and beyond, and the bokeh at larger apertures along with the falloff can produce beautiful results. The slight softness wide open makes it a terrific lens for portraiture...
Hope that proves fun for you!
Enjoy,
G