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lens confusion (why a positive element in a telephoto lens?)

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lens confusion (why a positive element in a telephoto lens?)

Postby wildfunguy » Sat Sep 29, 2012 10:31 pm

(It is beyond me why they call the individual lenses "lens elements" instead of just calling the whole thing something like "compound lens.")

My confusion arises in understanding how the two lens elements of a telephoto lens allow for greater optical zoom with a shorter lens. The two lens elements are a converging lens element followed by a diverging (magnifying) lens element. But my understanding is that one achieves greater optical zoom by magnifying a small portion of the light onto the sensor, so the usage of a converging lens element to ultimately achieve greater optical zoom is counterintuitive.
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