Okay, it's fixed!

Badwolf was right, it was the Cameras.dat. I don't think it was OLC's, since though I have it in my files I don't use it. It might have been the new freecam mod, since I use that, but I don't remember noticing it before.
Anyway, I used Silent 3ditor to copy the parameters from the stock one and paste them to the one I use, and it works great.
Thanks all!
Now I have to find out how to use it to make the UZO and periscope pictures fill the screen the way the binoculars do.