Unbelievable Madagascar September 14–October 1, 2007
				India Wildlife: On the Trail of the Tiger November 7–24, 2007
				Angkor Wat & Bagan—Temples of Cambodia and Myanmar January 17–31, 2008

Noise is the film grain of the digital world. Instead of the even, knobby texture found in even the slowest film, digital noise manifests itself as colored flecks or unevenly bright spots, chroma noise and luminescence noise, respectively. Noise results from random signals generated by the camera’s electronics. The longer the exposure and higher the ISO, the more noise the camera will produce.

There are many ways to suppress noise, including using Photoshop’s Reduce Noise Filter (Filter-Noise-Reduce Noise). Plugins such as Noise Ninja do a good job, as well. However, all noise suppression compromises sharpness—and sharpening adds noise. Balancing these conflicting attributes takes time and craft.

In some situations, a better tool exists. Take several identical images and blend them together. Since noise is random, it’s unlikely that the same pixel will be the same kind of noise pixel on each exposure. When you blend them together, the good pixels cancel out the noise pixels with no loss in sharpness. Of course, if anything in the frame moves while you shoot the images, ghosts appear in the frame—which may be interesting or disturbing, depending on the subject.

Here is how to do it, step by step.

1. Take several identical shots of the same subject. Don’t change the f-stop, shutter speed or focus.

 
To illustrate my noise reduction procedure, I shot four identical frames, all at ISO 1600 to generate the most noise. (LEFT) This is one of the four frames, before I reduced the noise. (RIGHT) An enlarged area of the original image shows considerable noise.

2. Open the images in Photoshop.
3. The first shot is the background layer. Keep its opacity at 100%.
4. Move the second shot over the background layer by dragging the image while depressing the V key. Pressing Shift when placing the image will snap it into perfect registry.
5. Set opacity at 50% for the second shot.
6. Add the third shot to the stack as before and set opacity to 33%.
7. And the fourth shot at 25%.

 

Stack four layers from four shots. As each successive layer is stacked onto the background layer, the opacity is reduced by an increasing amount.

Voila. With the Blend Mode set to Normal, you now have a gigantic file with much less apparent noise. If you are happy with the result, flatten the image and save it.

 
(LEFT) This is the adjusted image following the noise reduction fix. (RIGHT) The enlarged area shows dramatic noise reduction.

Be sure to check out James' latest book, DIGITAL PHOTOGRAPHY OUTDOORS: A Field Guide for Adventure & Travel Photographers, published by The Mountaineers Press.

All images Copyright © James Martin