The above quote is from @JamesJetel in the "Current State of Phase One" thread. I have been curious about this hard-stop topic. For most of my technical camera history I had the Alpa STC, so the largest image circle I could experiment with was 98mm (18mm shift horizontally on a 54x40 sensor). Over the years I've used the 40, 70, 90, 100s, and now the 138f Rodenstocks. I never saw a hard stop, even on the 100s, which technically only has a 70mm image circle. But I couldn't shift that much. I did have to mount the Alpa adapters on the back of the camera to avoid camera body vignetting on my longer lenses like the 100s (and the sk 150).I have actually emailed Rodenstock this very question, and even asked if there were any world in which the hard stop on the image circle could be removed. I’d gladly have the data, albeit deteriorated quality at the far edges of the frame, over those hard black stops. They said nope, and further that they’d not be making anything like an 18mm to satisfy the need further.
I currently have the Alpa 12+, which can combine for a 123mm image circle if I shift simultaneously in both dimensions, but the only Rodi lens I currently own is the 138f. It officially has a 110mm image circle, yet I see no hard stop out to my current image circle limit of 123mm. That got me wondering: is this hard stop thing we've been talking about really from the lens, or is it from the camera body? As far as I know, Arca only has lens extensions on the front side of the camera. There is no option to space the back away from the camera to avoid camera vignetting like you can with Alpa. [Please note I'm not trying to throw stones. I'm just trying to figure out the real story here.] I asked Steve Hendrix to do a test with the 70hr on an Alpa with the spacer in the back, and he sent me a 4-image stitch from the Alpa Pano (35mm horizontal each way plus 10mm up/down). That's an insane 137mm image circle. There is no hard stop on that image. It gets dark in the very corners, but not until beyond >130mm image circle. Yet the 70hr has always had an official image circle of 100mm. See below.
So my question: Is it possible this "hard disk" we've been talking about that limits Rodenstock lenses to their "official" image circle is really just the camera body vignetting? Has anyone done a real test to see the source of the vignette? Someone who can put the adapters / spacers on the back of the camera to see if there is a difference? Maybe there is a hard disk in there, but from what I can tell it is well beyond the official image circle.
70hr 35mm shift L/R plus 10mm rise/fall: