I've never used your APO-Rodagon 90mm f/4, but from the prices and comments from other people, it's a very good lens. On my GFX-based tilt-shift outfit, I use the competitor: a Schneider-Kreuznach APO-Componon HM 90mm f/4. If your APO-Rodagon is as good as my APO-Componon, you have an excellent lens.
You likely know this already, but tilt will not give you the depth of field you need in every case. There are lots of situations where you won't be able to avoid focus stacking. Have you run into those yet?
I use movements in nearly all my photography. It's a rare image I make that doesn't have one or more of tilt/swing and shift/rise/fall. I don't do table top work, but I do shoot at table top scales all the way up to landscapes. Mostly I work outside in rough conditions. As a result, I've assembled an outfit that covers 24mm through 150mm in quite light lenses that allow movements on a GFX 50R.
I used to do all my work with a Toyo VX23D digital view camera. You can see that setup here:
https://www.robdeloephotography.com/Pages/Toyo-VX23D-and-Fuji-GFX-50R The downside of the Toyo is it's quite heavy and bulk for a "field" camera; in the studio it's totally fine. I used to hump that thing over hill and dale all day long, so it's do-able. However, earlier this year, in anticipation of a full spring and summer of intensive field work, I built something 1/4 of the weight of my Toyo that provides most of the movements I need.
https://www.dpreview.com/forums/thread/4654358 If you like building gear and you have the skills and tools, you can certainly make something that will give you movements. But there are easier ways (including upgrading your Actus if you want to shoot GFX).
A good quality tilt-shift adapter is certainly an option. Mamiya made some very good lenses for 645. However, for table top work I think you're going to find a tilt-shift adapter limiting. Depending on the work you do, you won't be able to get some of the shots you need. I find the tilt-shift adapters do better at landscape scales than close-in.
You asked about focal lengths and fields of view. If you're shooting a 24mm x 36mm sensor now, a 123.5mm lens on GFX camera gives you the angle of view of an 87.5mm lens if you're comparing the short side of the frame, and 110mm if you're comparing the long side. Your 90mm on a GFX camera would be like a 65.7mm lens (short side) or 74mm (long side) on 24mm x 36mm.
Are you doing this for a living? If so, why not just get one of the new Canon tilt-shift lenses and call it a day? Those are superb. If you're shooting Canon already that seems like an obvious solution. If you want to shoot them on GFX, excellent adapters exist.
Rob
