The three great lies.

Started May 30, 2012 | Discussions thread
New MemberPosts: 23
Re: The three great lies.
In reply to Rriley, May 30, 2012

The only thing I disagree with you on, Lou (and you are my favorite poster on this forum, by the way), is the supposed advantage of FF over MFT in low light.

My husband and I have had a variety of FT and MFT gear, along with a Nikon D3 and Canon 5DMII, Sony NEX, Fuji X100, and Sony A900. We have found that, in low light, the smaller sensor + IBIS can offer at least parity with a FF kit, if not a full-blown advantage. Time and time again we have found that too shallow a DOF is a problem with the FF systems. Of course, you can simply stop the lens down in that case, but what happens in low light?

For a given DOF, the smaller sensor gives an exposure advantage of 2 stops over FF. FF, of course, has about a 2-stop advantage in terms of noise, so you can bump up the ISO on the FF camera by 2 stops, as Louis points out, to get the same exposure for the same DOF. However, the ISO advantage is maintained only when comparing the latest FF Nikon/Canon cameras (i.e., D800, 5DMIII) to the lastest/greatest MFT (i.e., the E-M5). The E-M5 has narrowed the gap between MFT and older FF models almost completely. Now add in the IBIS advantage (for static subjects): an average of 3 stops is afforded here. This can be matched on FF (more or less; that 5-axis IBIS on the E-M5 is amazing) but only with certain lenses and with the usual hit in size/weight that go along with fast, stabilized lenses (not to mention cost, but that's not part of the shooting equation, just the budget equation!).

So it comes down to this: in low light when a lens on FF must be stopped down to match the DOF on MFT, FF is close to parity with the E-M5 if it is the latest/greatest FF sensor and you are using an image stabilized lens. If, however, the low light shooting is of a static subject and you don't have the latest/greatest FF camera nor a lens with IS, then the E-M5 is the go-to camera in low light, with as much as a 5-stop advantage.

For example:

Imagine my husband and I are each trying to get a shot of our 2 cats snuggled together in their basket in low, available light. I'm using the E-M5 and my husband is using his Nikon D3. I take the shot with my 45mm f1.8 lens @ f/1.8, 1/10sec, ISO 3200 no problem. For the same DOF (to keep both heads in adequate focus), and from the same shooting position, my husband would have to use either his 70-200mm f2.8 IS lens @ 90mm, f/3.6, 1/10 sec, ISO 12,800 or a prime like his 85mm f1.4 lens @ f/3.6, 1/80 sec (since it has no IS), ISO approx. 100,000!!!. Which shot do you think would come out better? I doubt, too, that he could really get away with a 1/10 sec exposure on the 70-200 2.8 IS lens -- the IS just isn't as good as the E-M5 IBIS, and it can be much harder to hold that big, heavy lens steady.

For the kind of shooting I do, I find too little DOF in low light is more of a problem than too much DOF, and that IBIS pushes the equation even more sharply in favor of the E-M5 over FF. I only rarely shoot fast-moving subjects, and I only occasionally need/want to take full-length single-person portraits against close, busy backgrounds. My advice to those with FF envy is to take stock, in an honest and thoughtful way, of the kinds of photographs you really like to take, day in and day out. You may find, like I did, that the FF "advantage" in low light can be just the opposite.

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