I guess what I meant to or should have asked is this: are the Nikkor f8 and Schneider SA f8 lenses of the same optical type (Plasmats?), so their performance (assuming good copies) should be roughly similar? Or is there something special about the design of the Nikkor 90 f8? There were a few comments here suggesting it was the best of the f8 90s.
Gary
Yes, yes and no
. Bottom line is that there are specific tradeoffs in lens design. As you remove distortions, you impart aberrations and falloff and as you balance the design for absolute resolving power, you lose total contrast. So here, Nikon, Schneider, Fuji and Rodenstock all took slightly different stances on what they balance to. Nikkor leans to high contrast where Schneider is on teh opposite side leaning to absolute resolution.
Nikkor LF lenses arguably have the highest contrast. High contrast is often mistaken for superior resolution in an image because you can distinguish the edges better. However, in reality, the Schnider lenses I tested on my Air force resolution target with the Betterlight scanning back showed that the Schneiders out-resolved almost everything else. Rodenstock generally falls next after Nikkor in favoring contrast, but changed the bias on their APO S lenses toward resolution -- more in a minute*. Fuji is sort of next, or may be even lower contrast than most Schneiders depending on specific lens.
*With the Rodie APO S design they really pulled the stops out and figured out a way to maintain almost as high a contrast high contrast and get excellent resolution. But then Schneider figured it out pretty quickly too after that and released their newer APO L designs. At the end of the day, you'd be hard-pressed to distinguish a Rodie APO S shot from a Schnieder APO L shot, though IMO there remains a slight bit of smoothness advantage to the Schneider APO L and a bit more contrast in the Rodie APO S, but we are really splitting hairs at 100% pixel view when compared side-by-side and you'll never ever ever see these subtleties in a print of any size...
If I understood correctly, the interesting thing about the Nikon is the larger image circle?
Finally, IC specs vary from manufacturer to manufacturer, so you need to be careful when comparing, and generally the Germans tend to be less forgiving than the Japanese. Almost all LF glass *ILLUMINATES* well beyond its stated IC, but at some point resolution has fallen off to a less than acceptable level. And this will vary from sample to sample of the same lens, so manufacturers pick a mean and use that as the spec. In the case of Rodenstock, this might be 30LPMM resolution, where with Nikon it may b 20LPMM -- note that I do not know the precise values, this is just an example. The other item is actual manufacturing and QC tolerances, and these probably vary between manufacturers too. ("Bad" lenses are sold out the back door and get a 3rd party name stamped on them or sent back to the technicians to get re-benched and adjusted to come within spec.)
So we are talking about the same basic lens design with subtle biases between manufacturers that make a difference in how the lenses render -- but that difference remains pretty subtle, so at the end of the day, ANY of these modern plasmats if not damaged by some user in the chain of custody will all render quite well.
I would say the *only* reason to consider a switch is to get a uniform rendering of color, contrast and edge characteristics across your focal range -- and that is the precise reason I ended up with mostly Schneiders. But I could have been just as happy with a selection of Rodies. Nikkors in general I found too harsh in contrast, but like the color (my preference only). I found Fujis in general a bit to variable in color rendering, but liked the other characteristics. Rodies were cooler than Schneiders and a bit harsher on contrast, so why I ultimately ended up with Schneiders. But YMMV based on which criteria strike you...
Hope that helps!
BTW, here is an online chart that lists manufacturer specs for many 4x5 LF lenses:
http://www.largeformatphotography.info/lenses/LF4x5in.html
Here is a broader link to other LF format choices:
http://www.largeformatphotography.info/lenses/
Cheers,