Maybe the definite post, Ming Thein analyzes the different systems
A question of sensor size – Ming Thein | Photographer
I’m surprised not that the largest sensor with the biggest pixels wins in most categories, but that the results are so close at all; small sensors have really become quite good. (In fact, I suspect that if I’d had an RX100 handy, it’d probably be quite close to the OM-D despite having pixels similar in size to the Fuji.) The reality is that at moderate print sizes – removing resolution from the equation – differences in exposure and processing choices from one photographer to the next can well erase or even reverse the differences we see here. What this comparison does not take into account is that the compacts and the CFV must be shot at base ISO to achieve the best results, with considerable compromises above this; the D800E and OM-D will happily go to ISO 1600 without much penalty – making them significantly more versatile cameras. They also have more malleable RAW files – the D800E’s files especially seem to be very resilient and forgiving of exposure errors.
In the mix today are five cameras with sensor sizes ranging from jumbo (49.1x37mm) to minuscule (4.8×3.6mm effective) and spanning several generations of technology. The oldest – mid-2009 – is also the largest; the Hasselblad CFV-39 medium format digital back uses a Kodak CCD with 6.8 micron pixels. The sensor has no AA filter, but also no microlenses; this means purple fringing is kept to a minimum, but light-gathering efficiency suffers as a result. The CFV consistently required about a stop more light than the other cameras to achieve the same histogram exposure. The Nikon D800E has perhaps the best full-frame sensor going at the moment; it’s a CMOS known for incredible dynamic range and a very low noise floor. The OM-D’s 15MP Sony CMOS’ strength is color reproduction, though I suspect that’s as much due to Olympus’ algorithms as the sensor; curiously, it has nearly the same pixel pitch as the D800E – though in practice, tends to be about a stop noisier at the pixel level. The Fuji uses a proprietary EXR-CMOS sensor (not the X-Trans array) – whose RAW output ACR still can’t seem to get right, so I shot JPEG for this test – as befits how I’d normally use this camera. Finally, we have the slightly oddball Canon: though the sensor is a 1/2.5″, 16MP type, the design of the camera’s optics – part extending barrel, part internal lateral movement with a 90deg light path change via a prism to keep the camera 19mm thick and still offer a 28-330mm optical zoom – meant that it only uses the central 10MP portion, for a very, very small effective sensor size.