There's been a lot of speculation about the sensor in the news Olympus E-M5. Some have stated that it's the GH2 sensor, while others say it's the G3/GX1 sensor. Still others claim it's a Sony sensor.
Here's the answer from Olympus representatives during a Q&A today on the GetOlympus Facebook page:
Until someone from Olympus can verify the specifics, such as who manufactures the sensor and exactly what is different about the design/architecture, or such differences are verified by DxOmark testing, I'll remain skeptical that this is in fact a new sensor.
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I just asked mine:
Update: I didn't get any answer for my question. Let me explain where I'm coming from with this line of questioning:
In my opinion, other than the multi-aspect ratio nature of the GH2 sensor, the differences between the G3 and GH2 sensors are a curiosity with almost no practical consequence to the still photographer. It's true that the GH2 files seem to have a tiny bit less shadow noise at base ISO, whereas the G3 files seem to be a tiny bit better at very high ISO, but for all practical purposes they are the same. If the EM-5 has the sensor from either of those two cameras, then it has an excellent sensor. If it truly has a new sensor, then so long as the new sensor can match the performance of those other two, I will be completely satisfied.
Where it gets silly is when a camera manufacturer tells the sensor manufacturer to replace one weak AA filter with another weak AA filter and then call the sensor a "completely new design". I'm pretty sure we've seen this before with Nikon and Sony sensors, and we've definitely seen it before with Olympus and Panasonic sensors. There's no reason for them to tell us that it's a new sensor just for us to find out a few months later from DxOmark that the claims were "marketing speak".
I'm a believer in DxOmark. On many occasions, I've found that their results are revealing, and occasionally I find them to be useful from a practical standpoint. On the other hand, their results are often misunderstood and taken out of context. Small differences in DxOmark results are interpreted to be of practical consequence when they simply are not. For example, I've seen many times the claim that the GH1 has a better sensor than the GH2, a claim which no doubt is derived from the DxOmark results. On the other hand, I've yet to see a single person who switch from the GH1 to the GH2 have any disappointment in the image quality of the latter camera.
Even "large" differences in DxOmark scores can have relatively subtle practical consequences, as I demonstrated in a dynamic range comparison between GH2 and Pentax K5 files
The bottom line here is that I actually don't care whether the E-M5 uses a "new" sensor; however, I think the manufacturers and their marketing representatives ought to be forthright with their answers to our questions about the technology.