Another nice "bang for the buck" option in the ~100mm focal length range is the Schneider-Kreuznach APO-Symmar 100mm f/5.6. These are 6 element, 4 group lenses from the early 1990s. If you shop carefully, you can get an APO-Symmar 100/5.6 for under the arbitrary $500 USD or EUR 500 that is the threshold for lenses in this thread.
There's a whole lineup of APO-Symmar lenses, from 100mm to 480mm. Some are for large format film, but the 100/5.6 was made for 6x9 film. I consider this a plus because the smaller image circle of a 6x9 lens creates fewer issues, like unwanted stray light, than lenses with image circles for larger formats. The original APO-Symmar line was replaced by the APO-Symmar L line, which was a redesign; apparently this was motivated in part by issues relating to the glass needed for APO-Symmar lenses. I've read from an authoritative source that the Symmar lenses started with the Componon design, and the APO-Symmar (not the L versions) started with the Componon-S design. The lens block diagrams for the APO-Symmar 100/5.6 and the Componon-S 100/5.6 certainly show a strong family resemblence.
I bought an APO-Symmar 100/5.6 because I was impressed by its immediate predecessor, the Symmar-S 100mm f/5.6. I needed a Compur 0 shutter for my APO-Digitar 35mm f/4.6 L-88 cells, and found one in nice condition that had Symmar-S 100mm cells with what the seller described as haze in the front cells. The cells were heading for the bin, but on a whim I tried them out. Very impressive performance. That got me looking at the improved APO-Symmar 100/5.6, and Warren
@diggles sealed the deal by sharing some images he made with his APO-Symmar 100/5.6 that looked really good.
Long story short, even in the short time I've had the APO-Symmar 100/5.6 I have been impressed. The APO designation is not just marketing; it really does do well in situations where other lenses have nasty purple fringing. I shot it side-by-side with the Symmar-S cells this evening, and it is a nice step up. It's sharper -- not dramatically, but enough to notice. Contrast is much improved, especially on large shifts.
Both the Symmar-S and the APO-Symmar lenses can shift 25mm in landscape and give good image quality at the far edge. The APO-Symmar is better than the Symmar-S with a 25mm shift on my GFX 100S, which is not surprising because the angle of view was increased from 60 degrees for the Symmar-S to 72 degrees in the APO-Symmar.
Some other nice features of the APO-Symmar 100/5.6 are that it's almost entirely free of distortion within the image circle I can use; this is not surprising given that it seems to be a modified enlarger lens design. Light falloff is moderate; image quality is crisp and clean right across the circle within which I can shift in landscape (100mm); and on my F-Universalis, mounted on a flat board, there is no need to recompose when tilting and swinging. This last feature is a very nice bonus.
If you see value in studying MTF charts, here's the APO-Symmar 100/5.6, compared to the APO-Digitar 100/5.6. Look what the sagittal (radial) and tangential lines for 20 lp/mm at f/11 are doing in each chart (green arrows). On the APO-Symmar, sag and tan travel together on either side of 80% contrast right across the 33mm x 44mm image circle, and stay strong within the image circle that gives 25mm of shift in landscape on that sensor (which is at around the 55% position on the X-axis for the APO-Symmar 100/5.6). For the APO-Digitar at f/11, the sag and tan lines are just a smidgen higher on the Y-axis; they also stay strong within the image circle of the lens at the distance shown (which is not infinity for the Digitar). Not in debate here is that the Digitar is the better lens... but the APO-Symmar looks good too. The evaluation images I've been making suggest it's a good performer on my GFX 100S setup. The small size and consistent good performance at f/8 are a win.
I think I'm going to enjoy using this lens. And yes, I already had a perfectly good lens in this focal length range! The business case for the APO-Symmar 100/5.6 was not strong. But I'm not sorry!
The Fujinon EX 105mm f/5.6 I used to start this thread holds its own against the APO-Symmar 100/5.6. On that note, the Schneider-Kreuznach is possibly a very tiny bit sharper than the Fujinon EX 105/5.6 (but it could be exactly as sharp -- it's that close). The Fuji lens is lower contrast, but not by enough to worry about. And the Fuji isn't as well corrected for purple fringing (but it's fixable). The Fuji does shift the same 25mm, and does just as well in the outer reaches of its image circle. Because of the way the Fuji mounts compared to the Schneider on my F-Universalis, tilt and swing can require a lot of correction (but this is a minor issue). All in all, they're both good choices -- lots of bang for the buck.