All images shot at 16mm. f8 shows good sharpness across the frame, no significant improvement noted with +2 dioptre except possibly f5.6 sharpness improved.
Tests done with D700, Subal FE2 Domeport and 7cm extension.
This lens appears to perform nicely on FX with very acceptable sharpness beginning at f5.6 with or without a dioptre, and even f4 is not horrible. My impression is that this lens gives better edge to edge performance than the 17-35. Anyone interested in higher % crops, I can provide the files.
First the series without dioptre.
Edited by loftus, 15 April 2010 - 09:17 AM.