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ISO Sensitivity / Noise levels (contd.)

In-camera High ISO noise reduction

Canon first introduced 'High ISO Noise Reduction' on the EOS 40D. While the first generation of this feature only offered one level of noise reduction, its latest incarnation gives you three (Low, Standard, Strong) which can be controlled via C.Fn II-2. 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 fairly low ISOs. The 'Standard' setting seems to be, depending on your preferences, a pretty good compromise to work with. 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 vertical axis of this graph, standard deviation of luminosity on the horizontal axis (note that the standard deviation scale here has been extended compared to the graphs on the previous page).

Noise reduction crop comparisons (ISO 800 - 12800)

ISO 800
NR Off
ISO 800
NR Low
ISO 800
NR Standard
ISO 800
NR Strong
ISO 1600
NR Off
ISO 1600
NR Low
ISO 1600
NR Standard
ISO 1600
NR Strong
ISO 3200
NR Off
ISO 3200
NR Low
ISO 3200
NR Standard
ISO 3200
NR Strong
ISO 6400
NR Off
ISO 6400
NR Low
ISO 6400
NR Standard
ISO 6400
NR Strong
ISO 12800
NR Off
ISO 12800
NR Low
ISO 12800
NR Standard
ISO 12800
NR Strong

RAW noise

Finally let's take a look a the raw output of the EOS50D next to the ten megapixel 40D. Removing any in-camera noise reduction and processing the images using Adobe Camera Raw (without NR) gives us the nearest thing to a 'level playing field' for assessing the relative noise levels of the two cameras' sensors.

The higher pixel count of the 50D will inevitably show more noise at the pixel level. In principle this additional noise might be expected to average out such that the overall image noise is much the same. However the 50D's output at high ISOs shows significant chroma noise, especially in the blacks, which is substantially due to pattern noise (or 'banding'), although this isn't immediately visible in the crops. This is extremely difficult to remove in post-processing, and means that overall the 50D's high ISO output isn't necessarily as useable as the 40D's.

Canon EOS 50D
ISO 800
Canon EOS 40D
ISO 800
Canon EOS 50D
ISO 1600
Canon EOS 40D
ISO 1600
Canon EOS 50D
ISO 3200
Canon EOS 40D
ISO 3200

RAW noise ISO 6400 and 12800

At Hi1 and Hi2 (ISO 6400 and 12800 respectively) the 50D produces significant amounts of noise. Both settings should be striclty reserved for emergency use. If you compare these crops to the 'NR OFF JPG' crops from above it also becomes clear how much noise reduction the 50D's JPG engine still applies even with noise reduction set to 'Off'.

Canon EOS 50D
ISO 6400
Canon EOS 50D
ISO 12800
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