GH2 Image Quality

At the Edge of the City │ GH2 + Leica 45mm F2.8 │ 45mm F5.6 2.5s ISO160Whenever I get a new camera, I compare the image quality with my previous camera. This lets me know how much farther (if at all) I can push the new camera in marginal conditions: any gain in image quality will allow me to shoot in lower light and/or with a faster shutter speed.

So I check to see how image quality holds up as the sensitivity increases, using images from my old camera as a reference point. For the results to be relevant, I do the test at night under artificial light; in other words the kind of conditions that would warrant the switch to higher sensitivities. I choose an outdoor scene with enough fine structures in order to be able to judge at what point image noise starts to overwhelm detail.

Test Methodology
First of all, I compare image quality between cameras at the same aperture, shutter speed and approximate image brightness. That's to compensate for cameras where the sensitivity is either higher or lower than stated. As such different cameras may need different ISO values to achieve an image with the same brightness when both are set to the same aperture and shutter speed. This is the most relevant way I can think of comparing image quality. After all, I choose a specific sensitivity in order to achieve the desired shutter speed and aperture. And not the other way around.

For the test, the cameras where shot from a tripod using the self timer to release the shutter. I shot both the GH2 and the GF1 with the Leica Macro 45mm F2.8 lens with image stabilization switched off. Images were taken as close as possible to the same time and of the same scene so that lighting conditions are as similar as possible.

I then imported the RAW files into Lightroom tweaked the white balance and developed them using moderate sharpening and chroma noise reduction but no luminance noise reduction. For ease of comparison, I processed both cameras' files to 4000 x 3000 pixels. Obviously this isn't the only approach and other strategies will lead to different results. That's why I've provided links to the corresponding RAW files so you can experiment yourself.

Observations
The GH2 seems to be less sensitive than the GF1 at each ISO setting. Setting both cameras to F5.6 and the same shutter speed, the GH2's metering most of the time selected a 1/3 stop higher ISO – sometimes 2/3 stop. The resulting images were of approximately equivalent brightness, despite the different ISOs. So I would say that ISO1600 on the GF1 is equivalent to ISO2000 or 2500 on the GH2. Taking the discrepancies in sensitivity into account the GH2 image quality still seems almost a stop better than that of the GF1: judging from the 100% crops below, GF1 ISO1600 (approximately ISO2500 on the GH2) is similar to the GH2's output at ISO5000. Not bad at all.

Links to corresponding RAW can be found at the bottom of this entry.

RAW files:

GF1, F5.6, 3.2s, ISO 100
GF1, F5.6, 1/5s, ISO 1600
GF1, F5.6, 1/10s, ISO 3200
GH2, F5.6, 2.5s, ISO 160
GH2, F5.6, 1/5s, ISO 1600
GH2, F5.6, 1/5s, ISO 2500
GH2, F5.6, 1/10s, ISO 5000
GH2, F5.6, 1/20s, ISO 10000

Comments

[oluv]

there is one drawback. looking at both base-iso raws, you can notice that the GH2 files are slightly more noisý than those of GF1. this is a pity as the GH1 was already better in this regard, the GH2 seems to have lost this advantage at least at base-iso. if looking closely (with turned off chroma NR) it is obvioius that the GH2 shows more chroma noise even at iso160. it is better at higher iso though.

very good comparison btw. the color discrepanices might result from a preliminary adobe-color profile for the GH2. the difference in color is very pronounced in this example.

[Björn Utpott]

Hi oluv. There's usually a price for everything. You're correct, there is a little more color noise in the GH2 scene at base ISO. But that can be removed without any serious consequences. Greater luminance noise would be much harder to cope with.

As to the colour discrepancies, those caused me quite a lot of headache. I'm not sure which camera's processed files have the more accurate output. The GH2 does tend to hold saturation better at high sensitivities.

[Joan]

Bjorn, to my untrained eyes - a slight edge to GH2 at high iso. Congrats on the new camera!

[Björn Utpott]

Thanks Joan. My eyes are untrained as well, but if I stare at anything long enough I'll see what I want to see :-)

[Håkon Søreide]

Thanks for your test.

I have a Panasonic G1 and have been contemplating getting a GH2 for some time now, and this is the first proper test I have seen comparing what's the important difference: Raw files at same exposure and therefore equivalent ISO rather than nominal ISO - as well as shadows turning to black.

The difference seems obvious in the digital files when you look at them, but I took it one step further and printed the picture at A2, upsizing the 1/10s GF2 file to match the 1/10s GH2. No noise reduction. The difference becomes so great, it is virtually night and day (I'll send you a picture of the print if you wish). The GH2 ISO 5000 looks beautifully clean with its filmgrain-like noise, whereas the GF2 Iso 3200 is riddled with blue colour noise and useful only for gritty B&W conversions (also a guilty pleasure of mine from time to time - but I prefer starting with a clean file for more options).

The added megapixels don't seem to add any detail, so I would rather have seen what Panasonic could have done with the same sensor size and their improvements in high ISO performance - perhaps another half stop of improved noise might have been gleaned from it, but that aside, the gap is significant for someone like me who often shoots handheld shots of people and animals in available light where ISO 1600 and above is required to stop motion.

Just after printing it, I sent my order for a new GH2, and I am looking forward to confirming your test results with my own test shots. Thanks for showing everyone the real difference between the technical image quality of these cameras.

[Björn Utpott]

Thanks, Håkon. I try to conduct tests that are field relevant. That's why, like you, I think image quality comparisons conducted at the same aperture and shutter speed are more meaningful. After all, I don't look at a scene and try to decide what ISO I want to shoot it at. Also, scenes of bottles and paint brushes aren't what most of us encounter in our daily shooting. I have trouble relating to those kinds of test scenes on the major review sites.

I think you will find that the GH2 captures more detail. I did some tests of daylight scenes with a lot of fine detail and the GH2's files clearly out resolved those of the GF1. Whether it's a significant difference is subjective of course. I'm looking forward to your impressions of the GH2 and your own tests!

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