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ISO Sensitivity / Noise levels (contd.)

In-camera High ISO noise reduction

The GH1 has five levels of noise reduction from -2 to +2. The graph below shows the effect of the various settings from ISO 800 upwards. As you can see the difference, even between the extreme settings, is fairly small, particularly at ISO 800. The graph also shows that the overall noise reduction does not always increase evenly. It appears that at those steps the main focus is on chroma noise reduction, there might also be some sharpening of detail involved. In any case the image output with a higher NR setting looks visibly cleaner.

Indicated ISO sensitivity is on the horizontal axis of this graph, standard deviation of luminosity on the vertical axis (note that the standard deviation scale here is magnified 2x compared to the graphs on the previous page).

High ISO Noise Reduction Crops

  -2 0 +2
ISO 100
ISO 200
ISO 400
ISO 800
ISO 1600
ISO 3200

Noise reduction and fine detail

The biggest issue with noise reduction - especially luminance noise reduction - is that in the process of blurring away the noise it can also have a very destructive effect on the detail in an image, particularly the fine, low contrast detail you might find in hair, fur or grass. To better judge the effect on fine detail lost due to noise reduction we have shot our lovely model and produced crops from the feathers in the image. We have left out the +/- 1 noise reduction settings as there is not a huge difference between settings.

To check the effect of noise and noise reduction on low contrast detail we shoot our lovely model framed as shown here, with the new added feature of feathers. The very fine detail in the feathers will help to better judge the effect of noise reduction on fine detail.

Raw vs in- camera JPEG noise reduction low contrast detail comparison

Shooting in RAW gives you a slight advantage in terms of low-contrast detail at almost all ISO settings. Of course at higher sensitivities it's always going to be a compromise between detail and noise but with the RAW format you've got, depending on the RAW converter you are using, a much greater degree of control over the application of noise reduction and can mix your customized cocktail of chroma and luminance noise reduction.

  ACR RAW NR OFF JPEG NR -2 JPEG NR 0 JPEG NR +2
ISO 100
ISO 200
ISO 400
ISO 800
ISO 1600
ISO 3200
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