E-PM2 is better than GH4 in true low light?

mpgxsvcd wrote:

You have some good questions. Let me try to answer as many as I can.

These images were produced by stacking the RAW images together with flats, Bias, and dark images from their respective cameras. In camera dark frame subtraction was not done because it was done in the post processing stacking procedure with dark frames that I took with each camera after the light frames were taken.

I believe that temperature plays the biggest role here. Remember these are not just high ISO images. They are also long shutter duration images. The heat build up will affect the ISO performance especially on a hot summer night in the south.

I wanted to find out which camera produces the better stacked image. The single frame image from the GH4 might actually be better than the single frame OE-PM2. However, both of those single frame images is terrible when compared to the stacked image. Stacking works. Trust me.

The stock filter that takes out UV and IR light plus the narrow spectrum of Ha light was removed and replaced with a filter that blocks UV and IR light but let's in Ha light. The filter only affects light that gets in and not the noise. Since this object doesn't have a great deal of Ha light the difference in filter should be negligible.

Here are the single frames from each camera. These are the JPGs from each camera. Sorry I don't have access to the RAWs for both cameras at the moment so I can't post those.

GH4 Single Frame 2 minutes ISO 3200

E-PM2 Single Frame 2 minutes ISO 3200

I understand better now, but not fully because I've never done stacking. I'm assuming you took one dark frame for each camera after the 12 light frames. Does that work equally to taking alternating light and dark frames (i.e. 24 frames for each camera)?

Also, I highly doubt that heat would affect the GH4 more than the E-PM2. The GH4 is a tank with extensive heat sinking (as you mentioned for video performance). I just can't see how the E-PM2 could move heat away from the sensor better than the GH4, given that the IBIS doesn't allow for good heat sinking.

If your findings are correct and you made no procedural mistakes, then it's far more likely that it's the Sony sensor in the E-PM2 that handles this type of procedure better than the Panasonic sensor in the GH4.

Because the GH3 uses a Sony sensor, I'm wondering how it would perform on this test.