A few words on Equivalence and comparing systems

Started Apr 2, 2013 | Discussions thread
slimandy
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Re: On "f/2.8 = f/2.8" and "being anal"
In reply to Alumna Gorp, Apr 3, 2013

Alumna Gorp wrote:

Great Bustard wrote:

Alumna Gorp wrote:

"in other words, simply because 35-100mm f/2.8 on mFT is equivalent to 70-200mm f/5.6 on FF"

Jeez man, not again, a 2.8`s, a 2.8 unless your being anal.

Saying "f/2.8 = f/2.8" is no more or less true than saying "50mm = 50mm".  In other words, it makes no more sense to compare f/2.8 on mFT to f/2.8 on FF than it does to compare 50mm on mFT to 50mm on FF.

Nope a 2.8 is a 2.8, and any exposer meter will tell you so

Yes, but it is also still 35~100.

But your going on about DOF, a totaly different ball game.

You can measure it in terms of DOF or relative aperture; you'll still get the same thing.

A 100mm lens with an f2.8 aperture has an opening of 36mm. 100/36=2.8

If you say it is equivalent of 200mm on FF the opening stays the same so the relative aperture is 200mm/36=f5.6

Yes, it is in fact still f2.8, but it is also in fact still 100mm.

What we are discussing is equivalence in terms of FF. 100mm f2.8 ie equivalent to 200mm f5.6. Not anal, just fact.

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