I'd like to close the loop on this post in case anyone else is thinking about this lens.
I didn't buy the Apo-Digitar 60mm f/4. Rather, I bought the Apo-Componon Makro-Iris 60mm f/4. It's the industrial, machine-vision of the Apo-Componon HM 60mm f/4 enlarger lens and uses the V38 mount; I needed the Schneider adapter to get from V38 to 39mm x 1/26th inch thread. They're all the same lens, just in different mounts. Schneider did this a lot in creating its Digitar lens line to stay competitive when the digital shift was happening. Sometimes they tweaked the optical formula a bit, and sometimes they just re-housed what they had. You can see this for yourself in the Schneider lens data sheets.
The nominal image circle (60mm at infinity) is tight for shift on a Fuji GFX 50R sensor. However, for my purposes, where I mostly need tilt, and use shift primarily to correct the composition after base tilt, this is an excellent lens. Often the image circle specifications are optimistic. In the case of this lens, they're actually generous. At infinity and my normal shooting apertures (f/11-f/16) I can easily get 10mm of shift in landscape orientation.
The lens is absolutely usable at f/4, although it vignettes strongly at that aperture. Light falloff is nearly unnoticeable at f/8 and effectively gone by f/11. I use a lot of lenses for tilt and shift on my outfit. I found this Apo-Componon to be among the most
reliable in the sense that it focuses accurately at f/4, and tilt is no-fuss, no-muss. I don’t have to worry about the results with this lens. Colour and contrast are excellent. I've never seen an official claim that the lens is multi-coated, but it's modern glass and quite resistant to stray light, so it may well be.
Image quality is best at f/5.6 to f/8. However, f/11 is still superb, and I routinely use f/16 despite a bit of softening due to diffraction.
In short, if you need a 60mm lens for tilt and shift on a 44mm x 33mm sensor and you don't require large shifts, this is an excellent option in any of its variants (Digitar, enlarger lens, machine vision lens). The enlarger versions tend to be cheaper than the Digitar version, but the iris mount of the Digitar is a bit easier to use.
A lens review without some example photos is always unsatisfying! Here are a couple from a project I'm working on at the moment. I didn't record the apertures, but in all probability both are f/16 because I needed maximum depth of field even with tilt.
This first picture is a view of the Speed River in southern Ontario, from a bridge. In this tiny JPG it's not possible to see the homes in the far distance, across the field. They're 850 metres from the bridge where I'm standing, but in a high magnification view of the full image you can see the horizontal siding boards on the house. The boulder in the foreground is immediately below my camera position. In the full image, you can see the veins in the leaves that have been piled up against the boulder by the river's flow.
The local hiking club kindly installed a small footbridge over this intermittent stream that provides a bit of flow to the Speed River after a rainfall. In a magnified full resolution version of this image you can see the grain of the end cuts in the bridge boards, the veins in the leaves that the wind hasn't blown off the trees yet, and the tiny hairs of bark on the trunks of these eastern white cedars.
