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

Started Aug 16, 2015 | Questions thread
mattr Veteran Member • Posts: 3,532
Re: 2x zoom lens with same absolute aperture instead of extender ?

mermaidkiller wrote:

Using an extender (tele converter) has the advantage that the absolute aperture (in mm, not as f/ number) remains the same with the same lens which allows a relative bright f/nubmer without T/C and yet acceptable with T/C. E.g the bright 200mm f/2.8L with T/C results in a yet acceptable 400 f/5.6.

A zoom alternative (100-400 f/4.5-5.6L) results in a dim f/5 at 200mm.

Why not make a 200-400 f/2.8-f/5.6 which replaces a T/C and a prime lens ?

I would take it even further: Why not replace such 2x zoom lenses with primes and high pixel density sensors that are cropped accordingly? For example your 200/2.8 on a 5Ds would be equivalent to a 200-400/2.8-5.6 if 12.6 MP resolution are enough. Not long ago many photographers (especially with Nikon DSLRs) thought that 12MP is all they will ever need and I'm sure 100MP sensors will arrive in the not too distant future.

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