Noise: Still A Concern For Digital Photography
Quieten Down, There's Too Much Noise
I just wanted to share with you an issue that may prove problematic on occasions in your own photography. I'm talking about NOISE. To illustrate some of the concerns associated with noise I've included some photos from a Leica M9 camera.
There were many wonderful things about this camera, such as it's color rendition and, of course, the quality of Leica-M glass. However, the M9 camera, which I no longer own, incorporated a CCD sensor which produced extremely high levels of noise at even moderately high ISO. While there was a lot to like about the camera, and despite the fact that I was a long term Leica user, this was a deal breaker for me and I was happy to sell the camera.
These days my camera of choice is a Sony A7rii. It's noise characteristics, for both high ISO and long exposure photography, are wonderful.
Noise: A Simple Explanation
Noise is a consequence of your camera's sensor being heated up, as more current is passed through it, during long exposure times (e.g., 1 second or longer) or when set to relatively high ISO's.
Noise is generally more likely to become visible on images made with a smaller sensor camera rather than a larger sensor camera that's of a similar vintage from the same manufacturer. That's simply because the larger sensor (e.g., full frame) camera will have larger individual photo sites than is the case with a smaller sized sensor of the same pixel count.
Noise: Here Today and Gone Tomorrow
Noise can occur anywhere in your image, but noise will be noticeable in shadows and in areas of smooth tonality (e.g., blue sky, clear skin, largely texture-free wall). Conversely, noise can remain largely hidden in highly textured areas which is why, within the same photo, you're more likely to see noise appearing in a blue sky, but not in grass.
Noise can appear as white (i.e., Luminance) or colored (i.e., Chroma) dots on your photos. While loosely associated with grain, from the days of film-based photography, noise tends to have a less random and, therefore, a more even appearance than was the case with grain. Film grain is roughly round or tabular in shape while digital camera sensors incorporate light-sensitive, square pixels that are arranged in a grid pattern.
Noise: JPEG vs RAW
Under exposed images, particularly JPEG's, are more likely to display noise. With less data available, compared to that of a RAW file, it's often harder to remove noise from a JPEG file.
If you like smooth, relatively clean images but also like the idea of being able to apply a controlled grain-like look to your images, you could consider a workflow that produces clean images, but allows for the inclusion of digital noise in, for example, Photoshop.
Signal To Noise Ratio
The more signal (i.e., data) you have in an image the less noise you'll experience. The notion of Expose To The Right (ETTR) is, to my mind, the best way forward providing it doesn't result in an out of focus image resulting from camera shake or subject movement.
The ETTR technique simply requires that you expose your photo so that the highlight data has been pushed as far to the right hand edge of the histogram as possible, without actually touching that same right hand edge (which would indicate that it's actually spilled over the edge resulting in a potential loss of important highlight data).
A RAW image will usually appear too light and unsharp. Your job then is to process the image in a RAW Converter, such as Adobe Lightroom, until you achieve the desired result.
HDR and Noise Reduction
As the effect of noise is cumulative I apply some slight noise reduction prior to processing a series of images into a HDR composite. What's more I never add Clarity or Sharpening prior to producing the HDR composite image.
Be careful with how much noise reduction you apply as there's a trade off between noise reduction and sharpness. The more noise reduction you apply, the less sharp your image will become. As sharpening increases noise it's helpful to apply sharpening locally, thereby limiting it to only the areas that need it.
To actually see the benefit of noise reduction, on screen, it's a good practice to click on the photo to view it at 100% (actual pixels) magnification in the Develop module in Lightroom prior to applying the noise reduction. Then simply view the displayed area, before and after, to determine the effectiveness of the noise reduction.
While it's fine to work with the Luminance noise reduction slider in Lightroom, I'd stay away from the Color Noise reduction slider, other than what Lightroom already applies as a default value. That is unless you can actually see disagreeable color dots on your photos.
How much noise reduction you apply for general picture taking situations is dependent on your camera; exposure technique (e.g., ETTR); subject matter; ISO (and, where appropriate, duration of a long exposure); image processing application and the way you employ it; and personal preference. Here are the amounts of Luminance Noise Reduction I'd recommend, as starting points, for general picture making situations with cameras dating back to the beginning of 2011.
- ISO 100-400 Luminance 20
- ISO 800 Luminance 30 (Being old school I still rarely work at such a high ISO)
- ISO 1600 Luminance 30-50