Nikkors vary in quality depending upon the specific design. The longer large format focal lengths tend
to be universally good, but for 35mm and MF applications they offered budget versions too. Oddly,
I found that the 75/4 is excellent for 35mm use, using only the center of the field, though it would
be a rather poor performer for the 6x6 application it is officially marketed for. And it does have a bit
of focus shift the first stop down (so I always critical focus one stop down). Their better model for
actual 6x6 use is 5.6, with more elements. And among their intended 35mm products, the 63 is allegedly better than their 50's. But I only tangle with such things for casual work. Normally I reach
for my Apo Rodagon or Apo Nikkors.