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Thanks, I think I found one that's exactly what I was looking for with the help of a related apps rabbit hole. "Magic Viewfinder" has a series for a bunch of different cameras, here's the Nikon one I found https://play.google.com/store/apps/details?id=net.kadru.nikonviewfinderfree&hl=en .. It looks good. I have a lot of primes for landscapes so it's going to help me figure out shots.