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. Despite the fact that the 50D is the newer camera it shows visibly more chroma and luminance noise than the 40D. Considering the 50D's much more tightly packed sensor (4.5 MP/cm² vs 3.1 MP/cm² on the 40D) this comes hardly as a surprise. It would have been unreasonable to expect Canon's engineers to overcome the laws of physics.

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'.