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

mpgxsvcd wrote:

Everyone talks about shooting in low light. However, I don't think they really know what low light is. I shoot Astro-photography with Micro Four Thirds. Most of the time we are dealing with minutes for shutter duration instead of fractions of a second.

I have an Olympus E-PM2 that I had modified to remove the stock filter to let more Ha light in. Removing the filter worked well for objects that are primarily Ha light only like the Horse Head nebula. However, the modification really doesn't help much for objects like M27 that span the full visible spectrum.

I also have a GH4 that is unmodified that I typically use for Moon and planet videos. However, I hadn't tried it for AP yet. I decided to take 12 frames of the exact same object(M27 Dumbell Nebula) with both cameras and compare them.

I expected the noise to be less for the GH4 because it is supposed to have added cooling for the video modes that it has. It was extremely warm and humid that night but I used the exact same ISO, shutter duration, scope, filter, and number of subs for each camera. The details of that are below.

I think it is pretty clear that the E-PM2 has much less noise after stacking. I am not sure why this is happening but it definitely means that the E-PM2 is a great choice for Astro Photography. Olympus was selling the camera with the kit lens for $170 last week. Most people drop $200-$300 on a T2i for AP.

Let me know what you think.

Twelve 2 minute ISO 3200 images with an 800mm F4.0 Newtonian and a Light Pollution filter in my backyard. Stacked in Deep Sky Stacker with Flats, Darks, and Bias images.

Olympus E-PM2

Panasonic GH4

Olympus E-PM2

Panasonic GH4

The E-PM2 uses a Sony sensor while the GH4 uses a Panasonic sensor, however the difference in low light scores on DxO isn't that great. The GH4 ranks a little higher overall in total score but the E-PM2 ranks a little higher in low light.

The GH3 uses a Sony sensor, so I'd be interested in how the GH3 compares to the other two.

Also, I assume you stacked RAW images. If it was JPG, then differences in settings can affect the noise. I'd like to see one out of the 12 images (unaltered) that you stacked for each camera. I presume both cameras had the long shutter NR activated as well.

p.s. Sony sensors are known for their low light capability, although I'm leaning toward there being some other factor accounting for the result.

Also, are you sure that removing the IR filter wouldn't give the E-PM2 some advantage in this test. If you're not using an IR pass filter, then removing the IR cut filter allows a camera to take in more light, both in the IR and some wavelengths of visible light. I don't know if that would have a major effect on this test or not.