A: As of now there're no relationships to Canon, Nikon or one of the other ... Residual spherical aberrations are focus shifts when stopping down e.g. if the lens ...
Color fringing affects only the tangential curve, and it does not disappear as you stop down. So, if the sagittal and tangential MTF curves become more widely ...
Tele lenses usually are not flawed by heavy distortion and the 200 VR is no ... be visible, but stopped down at least one stop is no longer detectable in the field.
You have to stop down till at least f/5.6 till the issue is reasonably resolved at 28/75mm. The middle range is, once again, not quite as affected by this.
As usual, stopping down reduces the corner darkening considerably. From f/2.8 onwards it's no longer an issue except for really critical subjects.
Now it's not really coming as a surprise but the quality is breathtaking in this scope. The image quality is pretty much excellent from f/1.4 all the way down to f/8.
... the lens shows only a slight vignetting of around ~0,4EV (f-stops) at wide open aperture with virtually no edge shading. Stopping down reduces the light fall-off ...
At f/2, the vignetting is clearly visible (1.7EV) albeit not extreme. Stopping down to f/2.8 improves the light falloff substantially and it's mostly irrelevant from f/4 ...
While this is usually no problem, it is worth to note that this is somewhat ... Stopping down to f/2 resolves most of the issue and it's essentially irrelevant from f/2.8 ...
