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Do all macro lenses loose light at close focusing distances?

Started 3 months ago | Discussions thread
Ernie Misner
OP Ernie Misner Veteran Member • Posts: 9,506
Re: Do all macro lenses loose light at close focusing distances?

fzrTom wrote:

Ernie Misner wrote:

Do all macro lenses change effective aperture when focusing extremely close? Just curious because my Tamron and Nikon macro lenses all did that, but a friend says his Canon macro lenses did not exhibit that behavior. Thanks for your input.

Yes, it's physical (or optical).

in few words :

- the focal length of the lens is given for a point at infinity, so ray of light coming form the subjet are parallel

- when you get closer to the lens the rays of light are no longer parallel

- the effect of this is that the focus of the lens is thrown back: and thereby the focal length increases

- as the diameter remains constant, the real F/D increases

Very well stated and thanks for your reply!

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Ernie Misner
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