I'm guessing most ronars, nikkors or artars will cover 12x20 in the 24"/600 mm range. Check with other 12x20 users. I've heard the 14" Gclaron covers as well, but would want to check with someone who's tried it . I've used a 19" artar with a 8x20 camera with some movements. The manufacturers tend to be very conservative with coverage. My 12" gclaron just about covers 8x20 when stopped down a bit