BillB said:ahsanford said:BillB said:So, what would be the aps-c equivalent of a 50mm lens set to f4.0 in terms of framing, light gathering and DOF?
50mm f/4 FF would be the same...
- Framing and DOF as a 32mm* f/2.8-ish lens on crop (it's not exactly one stop, that's just a rough rule of thumb)
- Light gathering / exposure as any f/4 lens on any sensor. Sensor size doesn't change how aperture gathers light.
*Canon and Nikon have different APS-C crop, so it varies a bit.
But because light gathering and DOF do not work the same way w.r.t. equivalence, there is no perfectly equivalent situation.
(Someone straighten me out if I've misread that.)
- A
That's what I think too, and that is why I asked Fullstop to explain his notion of equivalence. He posts like the size of the sensor affects the exposure setting (an opinion shared by a surprising number of people), and I don't think it is so. How come a setting of 1/125 and f4.0 taken off my handheld Sekonic works for both my 5DIV and my ancient Rebel? I don't believe that you need a 70-200 F2.8 on an aps-c camera to get "equivalence" with a 70-200 F4 on a full frame camera, at least in any particularly meaningful sense.
Sensor size does not affect exposure setting - but it permits you to go one ISO point higher and/or get images with less noise.
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