Absolute intensity of an image

I read a line saying "In some cases we may not want the filter to respond to the absolute intensity of an image"

What is the difference between absolute intensity of an image and intensity of an image?

Answer 1

[Image Analyst]

Intensity is always a positive value so the absolute value of the intensity is the same as intensity. Of course I don't know the context for where that was said, which may help to understand what they really mean. Perhaps they mean "pixel value" which can be positive or negative depending on what the image represents. For example a topographic image may have values above or below 0 (sea level). Maybe they just generically called the pixel value "intensity" even though it's not really an intensity.

[DGM]

I think the likely distinction is between absolute intensities and some form of relative intensity. Of course, without context, it's hard to say what to do with that information. If this is part of medical imaging, I imagine there's a lot of scaling and normalization that happens between the raw image and anything that's visually useful. Might be related to that.