I know there have been many effective threads on how to get rid of it - but I'm curious as to what causes it and if it is only common to Canon as a Nikon friend told me?
It seems to show up against white mostly - of course.
Rgb Color Noise In Shadows
I know there have been many effective threads on how to get rid of it - but I'm curious as to what causes it and if it is only common to Canon as a Nikon friend told me?
It seems to show up against white mostly - of course.
Good tutorial here: http://www.cambridgeincolour.com/tutorials/noise.htm.
In a nutshell: There are two types of information in a color image; brightness (luminance) and color (hue and saturation), which equates to two types of noise; color and luminance.
The noise in the color channels can be corrected for separately from the noise in the luminance channel.
Noise is bad image data arising from random events and other factors as it relates to the sensors Signal-to-noise ratio. And you will see noise mostly in the shadow areas where the signal (digital data) is lower. This includes whites in shadow.
Color noise is generally perceived as more objectionable then luminance noise. Color noise can be removed with minimal degradation to the image. Removal of luminance noise, can leads to featureless images with significant loss of detail.
Noise reduction software like Noise Ware, Noise Ninja and Neat Image have separate controls for reducing color and luminance noise.
Color noise, the visible red and blue spots in the dark areas of high ISO Canon images is present because of Canon's approach to noise reduction in camera image processing. Canon chose to take this different approach compared to Nikon's. With some of the newest Canons such as the 40D there is an option to turn up the color or chroma noise reduction.Originally Posted by Bill McCrystyn
Nikon has choosen to be more agressive with color, chroma, noise and less agressive on luminance noise. This means that more detail is preserved and the noise that is there has more of a film grain type of look. Color or Chroma noise looks more like tiny colored poka dots.
Usually noise will be worse in dark underexposed areas but that is a different topic.
Robert
I Thank both Roberts for their instant response. As always your answers were complete and understandable. I will follow the tutorial link as well. You guys are great! Many thanks! I will subscribe to this thread should anyone else want to chime in.
Your welcome Bill. I am glad Robert expanded on my initial response as I got waylaid and was not able to finish describing the Canon vs. Nikon difference on noise handling.
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