(Nikon on FotoDiox Pro Adaptor)
15mm f3.5 AIS v Sigma 12-24mm f3.5-4.5
Crops (f11) Extreme Corner Crops
15mm / f11 / FotoDiox adaptor
12-24mm / 15mm
Unfortunately, the right adaptor doesn't eliminate the elderly Nikkor's tendency for aberrations. These crops are 100% from the extreme upper right corner (full frame).
If you can overlook the exposure difference in the original (adapted Nikon lenses consistently require about half a stop's underexposure), you may notice that the Sigma lens has a touch more light fall off than the Nikon, which is exemplary. This modest vignetting makes for a more attractive rendering of trees against sky above!
Both are superbly corrected for geometry: the Nikon, as previously noted, has the merest kink of barrel distortion compared to the ruler perfect Sigma.