A few words on Equivalence and comparing systems

Started Apr 2, 2013 | Discussions thread
Macx Senior Member • Posts: 1,433
Re: A few words on Equivalence and comparing systems

I understand the point of thinking about lenses in focal lengths and focal ratios, but for the purpose of comparing lenses for one system with lenses for another system, it would be much better to talk about what angle of view (or field of view) the lens is providing and the physical size of the aperture. It really cuts through to what is important with regards to framing, perspective, depth of field, diffraction and light, and the argument that "Angle of view = angle of view" and "Physical size of the aperture = physical size of the aperture" are easy to grasp.

Two systems using lenses that each provide the same angle of view and with the same physical size of the aperture are equivalent.

And I think that as we're finally moving towards a new paradigm of what the goal of exposure is in digital photography, the old idea about "f/2.8 is f/2.8" might also be slowly on the way out.

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