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ISO Sensitivity / Noise levels (contd.)

In-camera High ISO noise reduction

Like the Pentax K-7 the K-x features four noise reduction settings - off, low, medium and high. The default setting is medium. High ISO Noise Reduction settings can be changed via custom function 14. By default noise reduction kicks in from ISO 800 upwards but you change the threshold in custom function 15. The difference between Off and Low settings is fairly marginal at all ISOs and mainly affects chroma noise. The medium setting also contributes towards reducing luminance noise and appears to present the best compromise between noise and image detail. At the high setting a lot of the latter gets lost pretty early on.

  Noise Filter Settings compared
Off
Low
Medium
High

 

Indicated ISO sensitivity is on the horizontal axis of this graph, standard deviation of luminosity on the vertical axis.

High ISO Noise Reduction Crops

  Off Low Medium High
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 studio scene and produced crops from the feathers in the image. We have left out the 'Low' noise reduction setting as it only appears to apply chroma noise reduction which tends to have little impact on detail (fine contrast).

To check the effect of noise and noise reduction on low contrast detail we shoot our studio scene 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 you can see from the crops below, like most cameras even at the 'Off' setting the K-x still applies some noise reduction. The RAW shots show visibly more chroma noise but also a little more detail. The 'High' setting is very strong and blurs most detail away pretty much from ISO 1600 onwards. Of course at higher sensitivities it's always going to be a compromise between detail and noise but shooting RAW offers you the flexibility to apply your favorite method of noise reduction.

  ACR RAW NR OFF JPEG NR-Off JPEG NR-Medium JPEG NR-High
ISO 100
ISO 200
ISO 400
ISO 800
ISO 1600
ISO 3200
ISO 6400
ISO 12800
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