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ISO Sensitivity / Noise levels (contd.)

In-camera High ISO noise reduction

Like all latest generation Canon DSLRs the 500D features High ISO noise reduction with three levels (Low, Standard, Strong) which can be controlled via C.Fn II-5. Of course there is also an 'Off' setting. As you can see from the graph below the 'on' options appear to apply a fairly even mix of chroma and luminance noise reduction at all settings.

When noise reduction is set at 'Low' its effect is pretty marginal. The 'Strong' setting leads to a visible loss of detail from ISO 400 upwards. The 'Standard' setting seems to be a pretty good compromise to work with (although this of course depends on your personal preferences). Please note that the 'Strong' setting reduces buffer space in continuous drive, and that even at the 'Off' setting the JPG engine still applies some noise reduction to the image. If you want to get completely rid of NR shooting RAW is your only option.

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

  Off Low Norm Strong
ISO 100
ISO 200
ISO 400
ISO 800
ISO 1600
ISO 3200
ISO 6400
ISO 12800

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 'Low' noise reduction setting as there is not a huge difference between that setting and 'Disable'.

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 visible 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-Disable JPEG NR-Standard JPEG NR-Strong
ISO 100
ISO 200
ISO 400
ISO 800
ISO 1600
ISO 3200
ISO 6400
ISO 12800
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