Fast primes vs good zooms

Started 2 months ago | Questions thread
Tom Axford Veteran Member • Posts: 6,476
Re: PL12-60 vs P12-35 f2.8

motormatic wrote:

left eye wrote:

I generally avoid constant aperture zooms - the constant aperture is usually not optical but achieved by automatic aperture adjustment.

Whether aperture is fixed or variable has to do with where the diaphragm is located relative to the zooming elements. If any of the elements in front of the diaphragm move to zoom, the aperture will be variable. If only elements behind the diaphragm move to zoom, the aperture will be fixed.

Hobbling a variable aperture zoom that is actually faster at the short end so it can work as a fixed aperture is kind of silly. Can you think of an example of such a lens?

Do you mean aperture as entrance pupil or aperture as f-number?

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