Dynamic range, Canon DSLRs, and Shadow Noise – Dealing With It


Thanks in no small part to the release of the Nikon D800 and its excellent Exmor sensor from Sony, shadow noise has once again become a hot topic on Canon forums. To provide a brief summary of the fracas: the D800 boasts one of the most impressive sensors in any DSLR, not only because of its 36 megapixels, but because of its impressive dynamic range which is measured to be 14.4 Evs at ISO100. Canon’s new 5DIII by comparison has a measured dynamic range of 11.7 Evs. That’s not too shabby in the grand scheme of things. But, not only does it lag behind the D800, it does not improve at all on its predecessor, the 5DII, which is at 11.9 Evs. To compound the issue, Sony’s Exmor technology implements a unique (and patented) analogue/digital signal conversion which does wonders at eliminating noise, providing an unprecedented amount of latitude in post processing and the ability to lift shadows by amazing amounts.

On one side of the Canon camp, this has led to much consternation and hand wringing as EF-mount laden photographers gaze longing towards the other side of the fence, complaining that Canon has not provided any improvements to dynamic range in its latest generation camera. On the other side is a faction of Canonites poo-poohing the issue as trivial, saying that the existing dynamic range is adequate and the whole thing comes down to being able to expose properly so you don’t need to lift the shadows.

Both sides have a point, of course. Many photographers never run into dynamic range problems with their cameras; others do. While personally I have not found the dynamic range on my Canon 5DII to be a severe limitation, it is nonetheless a limitation to be aware of if you do extensive post processing. Here is an example of one such case.

The image above was shot at dawn in San Francisco and represents the 5DII at the limit of its dynamic range. The original raw file required highlight recovery to bring out the subtle texture in the clouds in the upper right corner. Meanwhile, the dynamic range on the shadow side was starting to block up in the lower left corner of the image. The issue here is I wanted the water in this bottom corner to appear as a more natural dark blue rather than black. This is where lifting the shadows comes in.

I ended up running the file through the raw converter three separate times with different values of exposure compensation, fill light, and highlight recovery to get the levels I wanted for the foreground, background, and sky. I manually blended the resulting images and then tweaked the overall tonal curves and color from there, plus applied a little bit of manual dodging in the midtones and shadows of the boat to bring it out a little more.

After all of this, the image looked pretty good on screen, but my goal was to make a 20×30 inch print. And at that size there was still a small but undesirable amount of shadow noise in the lower left corner. Time to bust out the noise reduction software.

The problem is, applying enough noise reduction to sufficiently smooth out the shadow noise also distastefully smears the image. So I did the noise reduction on a separate layer which I then reduced in opacity until it got close to what I wanted. Then with a large eraser brush (set to 0% hardness to blend softly into the layer below) I erased the portions of the image where noise reduction was not needed (highlight areas along the horizon and bright parts of the water on the right side of the image). There were also spots where some noise reduction would help (lighter shadows) but did not need to be as strong as the deep shadows, and on these parts I went over with the eraser brush set to 20%. After that, I flattened the image and tamped down a little more noise manually with the blur brush. Then I applied large feature sharpening with a software plugin (Topaz Detail), and then some local contrast enhancement using Photoshop’s unsharp mask tool (low percentage, high radius values). To finish it off I applied a slight amount of simulated film grain.

Below are crops of the bottom left corner taken from the 20×30 inch file showing the noise. Clicking the thumbnails will take you to the full size crops. The crops represent a 5×5 inch area on the full size print.

No noise reduction:

Strong noise reduction:

Final version:

The differences may be subtle, and on a postcard-sized print you’d probably never see it. But when a 5×5 inch corner of your 20×30 inch print is showing noise like this instead of nice smooth shadow tonality, well, that’s a bit annoying.

Granted, I don’t run into such issues very often. But would I love to have the D800’s clean shadows to work with? You bet. But, not at the expense of giving up my Canon lenses (I’m looking at you 24TSE-II). In any case, for those who do run into this issue, it is possible to deal with; it just requires a little extra TLC in your post processing routine.

This entry was posted in Equipment, Techniques. Bookmark the permalink.

Comments are closed.