The primary reason is that an FF sensor has about four times the area of an MFT sensor. It therefore accumulates more light (more photons) at the same exposure (same f-stop and shutter speed). The pixel size is of secondary importance. Even if we were to compare a 64 MP FF sensor with a 16 MP MFT sensor so that the size of each pixel would be the same on the FF sensor as on the MFT sensor, the FF sensor would be expected to do significantly better in DxO's tests.
The reason why MF sensor don't do as well is that they are lagging behind in terms of technology. If you could put four D800 sensors together into one MF sensor, the MF sensor would beat the D800 sensor for exactly the same reason you point out earlier in your post: greater total amount of light on the sensor at any given exposure (f-stop and shutter speed).
Personally, I would prefer to compare at the same photometric exposure; in other words the case where both sensors are recording the same image. I'm in the camp that believes a 25mm f/1.4 lens on m4/3 is effectively the same as a 50mm f/2.8 lens on full-frame. When using these lenses at their equivalent f-stops, the m4/3 lens will be creating a 2-stop brighter image on the sensor, and therefore the ISO will need to be lowered 2 stops to correctly record the same image.
Especially, do not forget the lenses.
...which up until this past month was how much you'd pay for a FF body.
Only if you intentionally buy every lens a few hundred dollars above their MSRP.
I agree that that's an interesting comparisons, though not the only interesting one.
So am I, as far as DoF, diffraction, and light accumulation (but not exposure) is concerned.
Agreed.
When shooting at higher ISOs and DoF is in short supply, I would agree. In this case, the MFT camera might even beat an FF camera as I showed here:
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Nikon use Sony sensors in their top models. Some of the difference in performance between the same sensor can be down to model variation. Some can be because of the algorithm tweaking done by all manufacturers. Oly for example have excellent jpeg colour. Even in RAW, different manufacturers apply different amounts of sharpening. But there is always a cost, there is no free lunch. Improving one parameter is usually at the expense of another. For example, when Nikon began using the Sony sensor, they seemed to get a little more out of it with cleaner shots but more investigation at the time showed that the Sony cameras retained detail marginally better.
Not quite that simple I am afraid. It's two stops between the E-M5 and the D800 at base ISO yes (and hardly anything between the D7000 and the D800 in spite of the fact that the D7000 has less than half the sensor area). Further, the difference in DR at higher ISOs (which is a more informative measure than the "sports" score in my opinion) between the E-M5 and the D800 is only about one EV, not two. This is borne out by visual evidence too. Have a look here:
All true. However, as you know, two systems with the same DR can have rather different visual qualities. For example, at base ISO the G12 (compact) has more DR than the 5D2 (FF), and I don't think you'd argue that the G12 has "higher IQ" than the 5D2.
I haven't looked all that carefully at G12 images and know next to nothing about its technical or other performance. Not all that interested in compacts. But I figure there must be a point where midtone noise becomes troubling and I am sure the 5D2 has less of that than the G12.
Thank you
Great input from a real user. The "calibrating lenses" bit has kept me away from DSLR's.The way they compare it now, the FF sensor gets 4x the light because it is able to handle 4x the light and lenses that provide 4x the light are practical and economical to make. You have to give the larger sensor the full benefit of its size advantage.
Sounds good to me. The 5D2 is a fickle basterd when banding rears its head at low ISO (and in landscapes this is exacerbated if you plan to do any PP at all), so I can pick up an OMD and landscape with my 14-45 without caveats. No tilt and shift, and no equivalent to the sunset spectacular Sigma 12-24 (the 7-14 is more expensive, but not as wide), but for the most part, I am sure the walkaround results will hold up, which means my 550D is moving to semi-permanent EF "digital teleconverter" duty. Heck, I am even impressed with the GH2 I picked up last week. The DR is still
