Stop Fearing Noise


We've been in a pretty reasonable place with digital cameras for the last decade or so. That place is simply this: at low or modest ISO values we have more than enough dynamic range for most scenes, and the source of noise in any image will be basically the randomness of photons, which are being (mostly) correctly recorded. 

The decade old Nikon D600, for instance, has more usable dynamic range than you'd typically need in modest light (~8 stops at ISO 1600), and plenty for high contrast outdoor scenes (11.5 stops at base ISO). 

Sure, you might see noise in the shadows or even sky on a D600, both due to the randomness of photons. That randomness thing seems to freak people out, but it shouldn't. You have three simple ways of dealing with it:

  • Expose so the shadows have plenty of light (perhaps take two shots at different exposures and combine them later, too).
  • Use noise reduction tools. 
  • If it's not color noise, just consider it to be some nice grain ;~).

Curiously, Adobe's noise reduction tools, just as with its sharpening options, tends to be very sub-optimal. Both seem to have been derived from Bruce Fraser's early work and not really brought into what can be done with present day technology. That said, if you're really just dealing with fixing the randomness of photons, Adobe's Detail sliders can generally be massaged to get reasonable results that don't show off the noise. 

Nik Dfine was a small step better than Adobe's built-in tools (still is). However, I'd suggest two tools that just run rings around the old school noise corrections: DxO DeepPrime, and Topaz Labs Denoise AI. The downside to these two, however, is that if you haven't kept your computer hardware up to date, they run slowly. Even with state-of-the-art hardware they're not instant. 

However, both do an excellent job of dealing with noise. 

Let me give you an example, and let me pull a camera out of the closet from 2005, the notoriously noisy Nikon D2x. As the light went down during this photography session, I started having to bump my D2x upward in ISO to keep the shutter speed up. I ended up at ISO 800—something you'd tend to avoid on the D2x—and this result:


Yikes. The detail appears to be missing. Is there even any "eye" left? Of course there is:


I could probably do better, but this was just processed quickly with Topaz Denoise AI at defaults and a bit of exposure correction. Here's my final full image:


Thing is, people have been doing things that make their encounter with noise even worse than it has to be. To wit:

  • Underexposure — Any underexposure is simply wasting dynamic range, and at higher ISO values you simply don't have as much dynamic range to start with. The more light that gets to the image sensor, the less you'll be dealing with random photons. If you keep finding yourself moving the Exposure slider (or Shadow slider) upwards in the Adobe converters, you're probably underexposing. Unfortunately, camera makers still aren't giving us the tools we need to assess true exposure with raw files, so we have to improvise (I outline one solution for the Sony cameras in my Sony books, I tend to suggest UniWB with the Nikon cameras). 
  • Auto ISO — Unbounded use of Auto ISO can get you into trouble fast. Accept Nikon's defaults on some of their current cameras and you may find yourself at ISO 25,600, and I can guarantee that you didn't let much light get to the image sensor in that case. Depending upon the camera, you'll start to see the dreaded color noise—indicating that the math is no longer working internally and that photon randomness is no longer the primary culprit—and the resulting noise gets tougher to mitigate, though not impossible. Understand your camera's capabilities; know exactly at what ISO the color noise starts to become clearly visible, and try not to exceed that ISO, if possible.
  • Unfilled Shadows — Way back in the early 1990's, Galen Rowell taught how to use fill flash in the outdoors to bring up shadow detail. Galen was using slide film with maybe six stops of dynamic range, which made this almost necessary to get useful data in the shadows. Galen's -1.7 stops fill flash was a go-to for any near-area landscape that had significant shadow, as it often did in the early morning and early evening times he was most often photographing in. It's worth carrying a small flash with you for fill work. The SB-500 produces plenty enough light for true fill flash use. But you also have to move away from Nikon's automated flash capabilities to get true fill, so you've got some learning to do.
  • Unfiltered SkyGalen also was using self-designed graduated neutral density filters to hold back bright skies. Typically, that was a two-stop soft edge filter, but he (and I) had three and five stop variants, as well. Of course today you can just use Photoshop's sky replacement (hint: photograph the scene for the scene, then photograph the sky for the sky; combine in Photoshop and you're really just using a quicker and potentially better relative to HDR). 

In the above example, only "Unfilled Shadows" would be an appropriate thing to consider. I believe I eventually put the flash on the camera to do just that, but the problem with that in this environment was that it was blowing out specular highlights in the water in the foreground, so I just tried to keep my exposure as "best" as I could make it. 

Fortunately, I have far better cameras than the D2x these days. Cameras that would not have any real noise issue with the same situation, and would be very easy to correct for what little noise they did produce in the data. Still, those four bulleted things I just mentioned are things I always consider as I photograph.

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