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ISO Sensitivity / Noise levels (contd.)

In-camera High ISO noise reduction

Like the D90 and D300, the D5000 offers four levels of extra noise reduction at higher ISO settings (800 and up). Off, Low, Normal (the default) and High. Off is likely only to mean that this additional noise reduction for High ISO settings has been turned off.

  Title
NR Off
NR Low
NR Normal
NR High

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).

In-camera High ISO noise reduction

  NR Off NR Low NR Norm NR High
Lo. 1.0
ISO 200
ISO 400
ISO 800
ISO 1600
ISO 3200
Hi. 1

The graphs and crops clearly show that the noise reduction settings do not have an effect until you reach ISO 800 - below that, the results are identical. Above that point, the additional noise reduction settings do exactly what the names suggest with low, normal and high applying increasing amounts of noise suppression to both chroma and luminance noise. This gives means the noise reduction settings (which only affect JPEG output or are recorded as the preferred rendering settings if you process raw files with one of Nikon's converters), give a direct choice between noise and detail - the higher the noise reduction setting, the more noise gets smeared away.

This replicates the result we saw in the D90 and appears to be a move away from the Nikon tradition of suppressing chroma noise more aggressively than luminance noise, which gave fairly color-accurate images with a luminance 'grain' that gave the impression of detail. There's nothing to stop you getting the same result by processing in RAW and applying more noise chroma than luminance noise reduction, of course.

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.

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

As the previous tests show, there's no difference in noise reduction until you reach ISO 800 but, from that point onwards, the differences are immediately apparent. The high noise reduction setting smoothes away all the fine detail at ISO 800 and more detail is lost as the ISO is pushed up to the point that even quite large-scale detail is blurred at ISO 3200. Turning noise reduction off retains a high level of detail all the way up to ISO 3200, albeit with a fair amount of noise creeping in. If retention of fine detail is essential for the type of shooting you're doing, the NR Off and Low settings are likely to yield best results.

  ACR RAW NR OFF JPEG NR-Off JPEG NR-Normal JPEG NR-High
ISO 100
ISO 800
ISO 1600
ISO 3200
ISO 6400
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