Received my Schneider f/4.5 90mm Apo Digitar (SAD) in the new shutterless mount. Since I have the Rodenstock 90hr-sw (HRSW), I can compare them directly. The reason for my interest in the Schneider is size and weight. If the quality is “close enough” to the hrsw, then I save 562 grams (933 vs 371 w/ caps). This gets me down to 8.3 lbs for a 4-lens 54x40 MF kit. I bet most “FF” DSLR kits weigh more. If I add the 250 SA for more reach, it totals 10.9 lbs. (5) lenses from 35-250 (24-162mm in FF).
This is the difference in size between the two. I included the 34mm adapter behind for reference, and because both lenses are "SB" mounts so they require that adapter.
Quick results on the IQ3100: At f/11, the SAD is nicely sharp to the edge where it begins to get dark around 96-98mm. The official image circle is 92mm. In my opinion, this is one time where Schneider has underestimated the useful image circle. It is not the HRSW, which is phenomenal everywhere in the image circle from f/8 until diffraction takes over. But the SAD sharpens nicely by f/5.6 unshifted and is what I would call very good at f/11 out to ~ 95mm. Vertical 18mm shifts are no problem (93mm IC), and horizontal 18mm shifts (98mm IC) are excellent to within a few percent of the corners at f/11.
Using this lens in the field is a dream. The 40.5mm filter thread is wonderful. I can permanently mount a small lens shade, and I already have step-up rings since my sk150 is also 40.5mm. I’ve used electronic shutter exclusively since the feature was released; for my use there are no downsides. It is different w/o the Copal shutter, though. On the negative side, it is a pain to use the lens cap vs. closing the copal shutter. I am used to dropping the lens cap into the camera bag so I don’t fumble around looking for it when I pack up or change lenses. With this lens you have to keep it in your hand or in your pocket. IQ4150 users won’t care since the whole black frame experience has essentially gone away. On the positive side, I have zero black frame errors from forgetting to open the shutter after taking a dark frame!
Here is a rough comparison:
HRSW @ IC-98mm f/5.6 = SAD @ IC-67mm f/5.6
HRSW IC-98mm @ f/8 = SAD @ IC-67mm f/8
HRSW @ IC-98mm f/8 = SAD @ IC-98mm f/11
…
You see the pattern: As things sharpen up, the SAD lags behind the HRSW by one f-stop or by std vs shifted IC. Rated 1-5, 5 being excellent:
Here is the f-stop series for the SAD at the image corner. Top row (tagged green) is the unshifted 40x54 IC – 67mm. Bottom row is shifted to ~ 95-97mm IC:
Although my test was not definitive, it does seem the SAD has less field curvature, at least at 5 meters. If I refocus the HRSW in the corner at f/5.6, results are excellent. Samples of the HRSW @67mm f/5.6; left is refocused, right side is before I refocused from the image center; you can see it is back focused. I should repeat the test to see if it was my focus error.
I tried the SAD up to f/16, but did not see a significant improvement at the extreme corners of the image circle. My conclusion is to shoot the SAD unshifted at any aperture I want. Shifted I will stick to f/11 or higher.
Dave
18mm L/R shift horizontal (f/14) and 18mm rise / fall (f/16), blended in PS: