How many profiles do I need?

Noise Ninja's noise profiles can contain more than a dozen annotation fields, covering everything from the camera model and camera settings, to the ambient temperature. All of these things can affect noise, but that does not mean that you have to create profiles for all the possible combinations of values. Normally, you will shoot with most settings nearly the same for all images, and you'll be varying only one or two attributes like ISO. Also, some parameters like shutter speed have negligible effect in "normal" shooting conditions.

Here is an approximate grouping of the relative importance of different attributes:

• High importance: Maker, Model, ISO, and Megapixels. For scanners, Film and Multisampling are important.
  
  
• Moderate importance: Sharpness, Saturation, Contrast. Depending on the camera, aprofile created using the lowest in-camera settings for these values might not yield good results on an image that was taken with the highest values for these same settings. However, the differences may be negligible for values that are close.
  
  
• Low importance, or camera/application dependent: Temperature, Shutter Speed, Illuminant, Quality, Color Space. Extreme values for these might be important. For instance, outdoor astrophotography may involve abnormally long exposures and/or cool temperatures.

For best results, try to create sets of profiles covering the "High Importance" attributes, with the "Moderate importance" attributes at or near the settings you use in day-to-day shooting. For specialized applications (for instance, long exposures or extreme outdoor temperatures), you might want to create profile sets that cover relevant ranges of those variables, too.

The key is to hold most things relatively constant, and not to worry about things that don't matter.. For instance, for a given camera, the Maker, Model, Megapixels, Sharpness, Saturation, Contrast, Quality, and Color Space will change only infrequently for most photographers. The difference between RAW and JPEG Fine quality might be negligible in some workflows. Shutter speeds between, say, 1/8000 second and a few seconds might have little effect on noise levels (though this depends on the camera). Illuminant and temperature probably don't have a big influence over the normal range of shooting conditions (though CCD cameras in particular may be sensitive to temperature when combined with long exposure times).

Don't get overly concerned about having a "perfect" profile. Noise removal is inherently heuristic, and there is some latitude in the noise estimates. As long as your profiles are getting you "in the ballpark" you should be okay. However, the flexibility is available to handle special circumstances, and annotations can help you to know whether a particular profile set is likely to yield good results for your particular shooting preferences.