Nikkor 28mm f/2 Ai-S

[Birna Rørslett]

Vintage lenses have usually an unknown history and unless you have owned itself all the time, who knows what battering they have taken.  The notion of a lens "built like a tank" is fallacious. Thus sample "variation" is more like the norm not the exception and pretty hard to resolve in comparisons.

[Robert Camfield]

Yes...sample variation may explain any perceived differences in the 2.8/2.0 comparison of the 28s present on that web site...which I mentioned was hardly definitive. Similarly, at one point I had two 28 3.5s...AI and AIS variants. The AI had markedly higher resolution than the AIS, which incidentally was in unused condition. I attributed the difference to sample variation.

Robert 

[richardHaw]

28/2.8ais is very temperamental, specially if serviced. 

when done incorrectly, sharpness is good at either end but rather mediocre at moderate distances

fine-tuning the CRC mechanism is never easy without a specialized tool

[Robert Camfield]

Richard,

Thanks for the comments...I wasn't aware of the characteristics you mention, and fine tuning...really? As in, perhaps, defining the gap between the two lens element groups CRC and regular....at least it seems to me that the movement of the two lens element groups by the helicoids would be more-or-less fixed, as the focus point is changed. Perhaps I simply don't understand what's going on.

Tks, Robert

[Robert Camfield]

Richard,

"...the movement of the two lens element groups by the helicoids would be more-or-less fixed, as the focus point is changed..."

The above is not correctly stated and should read "...the movement of the two lens element groups by the two helicoids would not be altered, as the focus point changed..."  In other words, the gap between the two lens groups - the CRC and unit set - changes as the focusing distance changes. However, any fine tuning, Richard, would seem to adjust the gap by a similar magnitude, at all focusing distances. Again, perhaps I don't understand what's going on. By the way, I reviewed your discussion of disassembly/reassembly of the 24mm f2.8 AIS. 

Sorry for the mistaken...Robert