What is the simplest way to minimize digital noise at high ISO levels?

January 14, 2013 at 6:44 am  •  Posted in Q&A by  •  0 Comments

I often photograph the interiors of old churches and cathedrals while travelling and I am rarely happy with the image quality I get at ISO 3200, called Enhanced H ISO with my old Canon EOS 40D. I do not want to use the complicated noise-reduction software that you recommended some time ago, but I definitely want to get high-ISO photos that are not grainy or mushy. What is the solution?
—Charles R.

There are a couple of techniques that you can use Charles, although upgrading to a newer camera (like the EOS T3, about $500) would be a good start. The superior sensor, processor and noise-reduction technology will provide much better quality at high ISO. Regardless of the camera however, take great care to avoid underexposure. A photo that’s too dark can be lightened in any type of imaging software but when you do that, any digital noise will become much more obvious. The graininess and mottled colour speckles can be unsightly and they can obliterate some of the fine detail in a photo.

If you take a shot and it’s too dark, set +1 exposure compensation and re-shoot. Make nice bright photos but don’t use too much exposure compensation; you don’t want a loss of detail in important highlight areas. Also turn Off any dynamic range expansion feature such as Active D-lighting or Auto Lighting Optimizer. A feature of this type uses extra processing to lighten shadow and mid-tone areas, also making the digital noise pattern more obvious than usual.

Most recent enthusiast-oriented cameras provide a menu item that allows for setting a desired level for High-ISO noise reduction. You should find at least two options. It may be tempting to set the very highest to eliminate digital noise almost entirely, but that’s not recommended. Excessive noise-suppression would produce an unnaturally “smooth” effect with serious blurring of fine detail. The default level usually provides the best results.

Consider shooting Raw (not JPEG) photos when using a high ISO. Open the photos in the Canon Digital Photo Pro software, or in Adobe Photoshop Elements 10 or 11 and use the tools available for Noise Reduction. These are not complicated at all, but you should experiment a bit to find the settings that produce the optimal results: a bit of visible digital noise but with great definition of fine detail (not excessive smoothness).

In the software, view the photo at 100% magnification on your monitor for the most accurate view of the effect of any noise-reduction tool.  If you’re using Canon Digital Photo Pro, double click on a Raw photo and then click on the NR/ALO tab at the top of the tool utility box that appears. Then, click on NR Preview to view a portion of the scene at 100% magnification. Tweak the Luminance and the Chrominance noise-reduction sliders slightly until you achieve exactly the desired effect. Then, click on Apply. Finally, click on File at the top left corner of the screen, and on Convert and Save to convert the Raw file to a JPEG or preferably to a TIFF photo.


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