Originally Posted by
Steve Goldstein
I have the same brochure in PDF. It doesn't explicitly say so, but the image circle numbers are based on 1:1 magnification. The spec table gives a 55 degree f/22 angle of coverage; plugging this into the formula for image circle at infinity gives a 125mm image circle. Nikon says 250mm, which can only be correct at 1:1 as the image circle at 1:1 is twice that at infinity.
Of course, this doesn't address the OP's original question about the range of "optimum performance".
Regarding MarkJ's comment in post 7, Rodenstock's literature says the 120mm and 180mm Apo-Macro-Sironar have 6 elements in 4 groups, so the design differs from the Nikkor-AM (he is correct that Schneider's Makro-Symmar is an 8-element design). The Apo-Macro-Sironar's 1:1 coverage is 336mm, significantly more than the Nikkor-AM's 250mm.
I have no info on the Apo-El-Nikkor so can't say whether the Nikkor AM is or isn't similar.
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