It's a 7x5 lens, it won't get even close to 10x8. You can easily find the coverage for a 210mm Tessar, but being f6.3 it'll have slightly better corner and edge sharpness wider than f22 (the recommended sharpest aperture) than an f4.5 Tessar or Tessar type lens.
The best of the Zeiss Tessars was the f6.3 and corners get softer with the f4.5 and f3.5 designs, this is why the late production Xenar's went back to f5.6 from 4.5/4.7.
Adding: Now I've got home the image circle for that older Orbit 8.5" lens should be about 245mm @ f22
Last edited by Ian Grant; 06-15-2011 at 02:36 PM. Click to view previous post history.