GH2 vs GF1 High ISO and Shutter speed

Started Dec 1, 2010 | Discussions thread
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coffeebean
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GH2 vs GF1 High ISO and Shutter speed
Dec 1, 2010

Just received the GH2 and immediately did some comparison with the GF1.

By now, most people already knows that Panasonic changed the ISO ratings in the GH2, which certainly seems to be the case according to DXOmark. I am only vaguely familiar with the technical details involved in DXO's measurements, but I am sure there are reasons why those measurements were done that way.

That being said, personally, the only meaningful definition of ISO for me is determined by the shutter speed required to produce equivalent exposure at equal aperture. I have done a quick test, which is probably over simplifying things, but perhaps some might find the following results interesting:

Using the 20mm 1.7 @ 5.6:
GH2:
ISO 200, Shutter speed 1/3s
ISO 800, Shutter speed 1/13s
ISO 1600, Shutter speed 1/25s
ISO 3200, Shutter speed 1/50s
ISO 6400, Shutter speed 1/100s

GF1:
ISO 200, Shutter speed 1/5s
ISO 800, Shutter speed 1/20s
ISO 1600, Shutter speed 1/40s
ISO 3200, Shutter speed 1/80s

More importantly though, visually, I think GF1 metering is producing images ever so slightly underexposed compared to GH2. It's difficult to put a precise number, but I suspect that at equal exposure, there is no tangible difference in shutter speed between GF1 and GH2.

Below are a series of GF1 and GH2 RAWs (lightroom RC converted) ISO200-12800 samples.

Zero noise reduction up to ISO3200. Light NR applied to ISO6400+ just to see what is possible.

100% crops at ISO3200

In general, I'm pretty happy with ISO1600 on the GH2. These is one problem I am finding now however. If you take a close look at the bottom right corner comparison in the 100% crops, there appears to be a hot pixel in the GH2. It is always in the same position/frame. Invisible at base ISO, and starts to become visible at ISO800+. Now, I've counted over 2 dozens(!) of these bright green pixels, so I'm now wondering whether I should get a replacement camera.

I should note that I see hot pixels only in RAW. In JPEG/Videos, whatever Panasonic did, they made it absolutely spotless. This is somewhat annoying because LR can't clean these up at all. I'd be very interested in hearing what others find with their GH2 raws...

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