Did some down and dirty pool tests today with the Nikon f4VR 16-35. Overall this lens appears to be very sharp. As expected f4 edge sharpness is lacking, f5.6 begins to show improvement with very acceptable sharpness particularly with a +2 dioptre. Ignore the softness of the pool background at the bottom as the pool wall begins to slope upwards here.
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.









