Canon includes a custom function in their EOS-1D Mark III, EOS-1Ds Mark III, EOS 40D and EOS Rebel XSi models called High ISO Noise Reduction, which is turned off by default. This is a great new feature in Canon digital SLR cameras IF you understand how it works and when it works.
Digital SLR Noise
When a digital SLR camera is used at higher ISO settings, it will tend to generate more noise in the images it produces than at lower ISO settings. This usually occurs at ISO setting such as 1600 or 3200. There are two types of noise generated, Luminance and Chrominance.
Here’s What’s Important
Canon’s High ISO Noise Reduction custom function only works on Chrominance noise and only on images that are processed “in camera” from RAW to JPEG. That’s right. ONLY on Chrominance noise and only on images processed “in camera”.
What About RAW files?
Since RAW files are “developed” off camera using a variety of software products, the Canon High ISO Noise Reduction setting has NO EFFECT WHATSOEVER! Having said that, Canon’s RAW Image Task software will read the CR2 file and if the High ISO Noise Reduction function was enabled it will apply chrominance noise reduction similar to what the DIGIC III processor does. The High ISO Noise Reduction custom function will have NO EFFECT WHATSOEVER on Canon’s Digital Photo Professional (DPP) software like any other RAW processing software such as Adobe Camera RAW or Lightroom.
Setting the Record Straight!
If you’re a wedding photographer or just someone that prefers JPEG files and shoots in low light conditions, this custom function can make a huge difference in the quality of your images. However, if you shoot RAW and perform your post-capture processing in Adobe Camera RAW or Lightroom, then leaving this function disabled makes much more sense! Especially since this custom function reduces the maximum burst rate significantly.
Straight from the Horse’s Mouth
Canon has published a great article on their High ISO Noise Reduction custom function that goes into great detail about this often misunderstood setting. This article cuts through the marketing propaganda finally sets the record straight for RAW shooters like me.
All I can say is “It’s About Time!”