I would love to say that I have a highly tuned vision of what 355mm on 7x17 or 72mm in 4x5 pinhole looks like when looking at a scene but I don't. I have a vague idea and as those 10,000 hours pass I'm sure I'll get better but for now...
Old school meets Modern technology. No card mask, or variable optical view finder for me. I use Cadrage "Directors Viewfinder App". It's designed for Videographers/Film makers to get an idea of what lens to use on what camera taking into consideration sensor size, focal length etc. It has a heap of built in cameras and lenses but you can completely configure it for anything.
Setting up 7x17" sensor size with 355mm G-Claron and 4x5 sensor size with 72mm was a breeze. You can add multiple focal lens to each camera and scroll through them to see have they affect the scene.
The app is simple to use. It uses the phones camera and presents an impression of the view with the selected camera/lens. You can save a preview and all the metadata is captured such as location, camera, lens, tilt and bearing.
I use this two ways. One for wandering around scouting for scenes to come back to that would suit the 7x17. It's not a setup to just stroll around with, you need an idea of what, when and how before you turn up and setup.
The other way is as a pinhole viewfinder. It's still a little hit or miss but holding the phone next to the camera whilst lining up you can compose with reasonable confidence. Zooming with your feet and adjust angle as required.
Would definitely recommend... 👍