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

Started Feb 3, 2013 | Discussions thread
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Samuel Dilworth
Regular MemberPosts: 249
Re: And to conmplicate matters, there's also the "T-value" to consider
In reply to RBFresno, Feb 4, 2013

RBFresno wrote:

Of course we've been talking of the physical aperture size relative to the focal length when we speak of f-stops.

That’s not strictly accurate, and might be confusing in the context of this thread. The f-number at infinity is defined as the focal length divided by the entrance pupil diameter, not the ‘physical aperture size’. The entrance pupil and physical diaphragm diameters can be different because lens elements in front of the diaphragm can change its magnification.

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