Micro-Nikkor 55mm f/2.8 AIS

This lens is generally regarded as one of the sharpest Nikkors and a true flat-field macro lens when used either alone or with PK-13 extension tube. In fact, the two are designed for each other (and was sold as a pair) so that the lens alone is very lightweight and compact (as compared to later AF versions of 55/2.8 or 60/2.8) for magnifications smaller then 1:2, and used with PK-13 for magnifications between 1:2 and 1:1. I tend to believe so since the magnification ratios when used with PK-13 are also engraved on the lens barrel.

However, In my slide duplication experiments, occasionally I forgot to close down the lens diaphragm and left the aperture at f/2.8. (In the experiment, I wanted a slightly larger than 1:1 magnification, I used BR-2A and BR-3 coupled to form a short extension tube but lost the automation of lens diaphragm.) The image is extremely blurred at corners. So, I doubt the "flat field" claim of the lens. If the lens is truly flat field, it means a flat slide surface should all be sharply focused although sharpness may degrade a bit at corners. But what I see is out of focus image at corners. So, when duplicating slides, I have to use small apertures. I am very disturbed with this finding. I'll run some test later to see what's going on.

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Last updated: July 18, 1997.