Today’s Question: I almost always shoot at ISO 100. Consequently, there is very little noise present most of the time. I’m never quite sure whether to reduce the barely noticeable noise or if I should just leave well enough alone. What do you do in such a situation? I have never really read or heard anyone address this problem about when or when not to reduce noise shot at lower ISO settings.
Tim’s Quick Answer: Even when noise is minimal in an image, I recommend at least applying color noise reduction. I would only apply luminance noise reduction if the noise was significant enough to detract from the overall quality of the image.
More Detail: Noise is unavoidable in digital photos, so the real question is how much noise is present. Even under optimal conditions, however, if you can see color noise when you zoom in to a 100% zoom setting for the image, I feel you should apply color noise reduction.
When applying color noise reduction, it is important not to be too aggressive. In some cases, you may be able to remove all visible color noise. However, if you apply settings that are too strong you may cause color artifacts due to the averaging and blending of color values caused by color noise reduction.
With luminance noise reduction the risk of causing problems in the photo are more significant. Strong luminance noise reduction will have the effect of blurring the photo, reducing the amount of texture and detail that is apparent in the image.
Therefore, when applying luminance noise reduction, it is especially important to carefully evaluate the settings, striking a balance between reducing the perceived noise and retaining texture and detail in the photo.
Based on all of this, I would generally apply color noise reduction for any image where you can see color noise. I would only apply luminance noise reduction if there is a fair amount of luminance noise, to the point that the noise is clearly contributing to the appearance of reduced image quality. If luminance noise is minimal or barely noticeable, I would tend not to apply luminance noise reduction.