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Low light high ISO comparisons

The Panasonic Lumix DMC-GX1 uses the company's latest generation 16MP sensor, which places it alongside the highest resolution Micro Four Thirds cameras currently on the market. While this is the same sensor first seen in the Lumix DMC-G3, Panasonic has suggested that the noise reduction performance of the GX1 has been adjusted, which seems reasonable given that the GX1 sports a top ISO of 12,800, a full stop higher than the G3.

Physical sensor size can play a crucial role in high ISO performance. All else being equal, larger sensors have the potential to deliver lower levels of image noise. Of course, that's only part of the story and where in-camera JPEGs are concerned, image processing algorithms can produce observable differences even in cameras sharing the same sensor.

Below we compare the noise performance of two Panasonic Micro Four Thirds models, the GX1 and G3, along with the Sony NEX-5N which uses a 16mp APS-C sensor. The in-camera JPEG images you see here were all photographed at ISO 6400 under low color-temperature (2600K) artificial light, designed to be representative of typical indoor lighting. This accentuates the appearance of noise due to the low level of blue light in the spectrum of the light source. This means that to achieve accurate white balance the blue channel has to be amplified strongly, and the green channel to a lesser extent - thereby increasing the visible noise. Each camera was used at its default noise reduction setting.

Panasonic GX1, ISO 6400 1/20 sec f/6.3
NR 0
100% crop
Panasonic G3, ISO 6400, 1/20 sec f/6.3
NR 0
100% crop
Sony NEX-5N, ISO 6400, 1/13 sec f/8
NR Standard
100% crop

Examining fine edge detail in the 100% crops above, you can see that the GX1 and G3 show extremely similar performance at NR 0. While we're inclined to give the GX1 a slight edge for better color saturation and marginally less objectionable artifacts, both of the Panasonic cameras show just how impressive the company's 16MP sensor performs in combination with in-camera image processing, retaining a discernible amount of detail while suppressing chroma noise.

Yet it's easy to see why the 16MP Sony NEX-5N is so well-regarded for high ISO output. This APS-C sensor camera not only resolves more fine detail than the Gx1 and G3, but shows far less luminance noise and significantly fewer image processing artifacts.

Interestingly, while the GX1 and G3 in-camera JPEGs are almost indistinguishable at NR0, Panasonic has made some changes in image processing at the maximum noise reduction level (NR+2). It is here that the output of the GX1 offers a significant benefit over the G3.

Panasonic GX1, NR +2 Panasonic G3, NR +2
100% crops

Looking at the 100% crops above, it is obvious that the GX1 strikes a more successful balance between detail preservation and noise reduction. The indiscriminate smearing seen in the G3 has been replaced with a seemingly more sophisticated and selective approach in which priority is given to maintaining low contrast detail. In the bottommost pair of samples you can see that along with such aggressive smearing in shadow areas, the G3 introduces a magenta hue while the GX1 maintains a much more neutral black.

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