A different way of looking at the focus breathing of the 70-200mm f/2.8 VRII

Started Feb 3, 2013 | Discussions thread
Leonard Shepherd
Leonard Shepherd Forum Pro • Posts: 12,956
Re: And a better way to look at it…

Samuel Dilworth wrote:

Leonard Shepherd wrote:

I disagree. The only lenses which you do not gain or lose some exposure relative to the marked aperture in the Nikon line up are the 50mm f1.8's and the 85 mm PC.

(snipped). None of these explain the differences noticed by the thread-starter, which are caused by:

  • the roughly one stop difference in f-number between the f/2 prime and the f/2.8 zoom
  • big differences in vignetting at large f-numbers (affects off-axis image)
  • differences of field curvature and astigmatism (affects off-axis image)

Ignoring which prime, the 200 mm macro, the 200 mm F2 and either aperture current 70-200 have different optical constructions, different effective apertures at minimum focus and different minimum focus distances.

Variations in the different lens designs is to be expected. In the context of this thread the 200 mm f4 macro "breathes" a lot being effective 125mm f2.5 (compared to a theoretical symmetrical lens design) by 1:1 magnification.

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Leonard Shepherd
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