Maximum aperture at 1:1 macro

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WFulton Senior Member • Posts: 2,697
Maximum aperture at 1:1 macro

It is well known that a macro lens at 1:1 (magnification 1x) numerically loses 2 stops of light due to focal length increase at close focus extension. A f/2.8 lens becomes f/5.6 at 1:1, and f/16 becomes f/32.

Modern macro lenses often report this new actual f/number change, however a Nikon f/2.8 105 mm macro lens reports a new maximum of f/4.8 at 1:1. That is not f/5.6, it's about 1/2 stop difference. This lens manual page 124 shows a graph with the f/4.8 number.

How do they do that? It is internal focusing, but still, how can they do that? Do they actually open the aperture more?

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