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2x zoom lens with same absolute aperture instead of extender ?

Started Aug 16, 2015 | Questions thread
Great Bustard Forum Pro • Posts: 45,641
Sorry, but you are 100% incorrect.

Michael Fryd wrote:

Steve Balcombe wrote:

...

Yes, but as per my earlier post the front element of a long lens is the size of the entrance pupil. The shorter the lens, the less true this is.

...

The aperture is the weakest link in the chain. Typically, that will be the size of the front element, but that's an engineering decision, not a requirement of physics.

The diameter of the aperture (entrance pupil) is typically significantly less than the diameter of the front element, but the diameter of the front element will tend to approach the aperture diameter as the lens gets longer.

Thus with a zoom lens, there are times when the effective maximum aperture is smaller than the front element.

Not "there are times", but pretty much always.  The only exception *might* occur when a long zoom is wide open at the longest focal length when the aperture diameter and front element diameters are equal.

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