I have a camera that's been set up for a very specific application: it's a mirrorless Sony alpha 6000, with the lens that came with the camera: The Sony 16-50mm f/3.5-5.6 OSS Retractable Zoom Lens.
I don't need to zoom, I don't need to focus, as it will be used in a situation where I always have it focused on the same object the same distance away, and I also have it zoomed to maximum of 50mm, which according to the sony website is 32 degrees FOV.
What I would like to do is make this more 'foolproof' by replacing the lens with a fixed lens instead. I thought this would be as simple as buying a 50mm lens, but the A6000 is an APS-C sensor, which means I need to figure out what '50mm' means when the E-mount lens might be a full-frame lens, or an APS-C lens.
So my question is: Without literally buying 3 lenses and taking them home to test, do I calculate exactly which fixed lens is the same as the lens I have zoomed in? If I buy a full-frame lens, does that mean I need 35mm (50mm / 1.5), or do I get a 50mm full-frame lens? or it 50mm * 1.5 -> 75mm APS-C lens?
A few degrees field of view either way isn't a big deal.