A few words on Equivalence and comparing systems

Started Apr 2, 2013 | Discussions thread
Sean Nelson
Sean Nelson Forum Pro • Posts: 12,800
Re: A few words on Equivalence and comparing systems

richarddd wrote:

Sean Nelson wrote:

I'd be choosing M43 because I deem it "good enough" for the kinds of pictures I take and the uses to which I put them.   In other words, I'd be accepting the fact that I'd have a smaller envelope of shooting conditions under which I can get the kind of shots I want.

Taking pictures from the same position under the same conditions with a 12/2.8 m43 and 24/2.8 FF will produce different DOFs and, assuming similarly efficient sensors, different amounts of noise.  For many, that would mean the lenses are not equivalent.  Are DOF and noise unimportant picture characteristics for you?

DOF is one of the characteristics of the envelope I described.   Yes, when I choose a camera with a smaller sensor and associated lenses of similar speed (f/ratio), I sacrifice DOF flexibility.  If I'm willing to accept that compromise, then I've narrowed my shooting envelope.   If I'm shooting pictures within that envelope, the fact that I could achieve smaller DOF with a larger-sensored camera (and associated lens) is irrelevant to me.

My worldview is to understand that the camera/lens choice reduces the envelope.   Therefore if I'm happy to live within the smaller envelope then "equivalence" arguments are really pointless.   I really don't care if a particular lens is inferior to it's FF "equivalent" because I've decided I'm quite happy living with the limitations of the smaller format and its lenses.

It's kind of like arguing that a semitrailer can haul more stuff than a pickup truck and can move X tons of freight more economically.   Most pickup truck owners know this when they buy their vehicles and they would get really annoyed if semi drivers keep constantly pointing it out to them.

Macx wrote:

How the sensor behaves in a camera is definitely a big part of how well the system as a whole performs, but don't underestimate how much the lenses matter. It's easy to think of the envelope being defined by the sensor performance, when instead it's the slower lenses that creates these limitations.

That's very true, and the introduction of focal length reducers such as the Metabones adapters really underscores this point.   Using one of these adapters, an M43 camera with the same lens has the same field of view, depth of field and total light gathering performance as an APS-C camera despite its smaller sensor.   The proliferation of f/0.95 lenses for M43 is another reflection of this.

But again, if you have no need for those lenses then it's a bit of a moot point.

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