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

Started Aug 16, 2015 | Questions thread
MitchAlsup Veteran Member • Posts: 5,518
Re: 2x zoom lens with same absolute aperture instead of extender ?

But you are not measuring the size of the entrance pupil! You are measuring how much of the lens can be seen through the viewfinder--which needs to be the whole lens (or the manufacture would save money by making the lens smaller.

You can observe the size of the entrance pupil by opening up the aperture all the way and see how much of the view finder you can see from the front of the lens. Hint: its a lot smaller than the size of the objective. The objective is large because it has to fit multiple entrance pupils across its face in order to fully illuminate the off axis portions on the sensor.

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Mitch

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