What do colour calibration and Background Neutralisation actually do?

[stevek]

^^^^
?

I know they are important steps on the RGB chrominance but I see little change in the image when i actually perform these two functions.  What is going on in the background?

Neutralizing the background?  With respect to what?
Calibrating the colors?  With respect to what?
Many thanks,

Steve

[Geoff]

http://pixinsight.com/forum/index.php?topic=2542.0

[Alejandro Tombolini]

Hi Steve, those tool are explained in the documentation of the tools.

From BackgroundNeutralization:

The background neutralization task equalizes the average red, green and blue components of a color deep sky image to yield a neutral gray rendition of the sky background. Neutralization is carried out by applying per-channel linear transformations computed from a set of pixels sampled on a background reference image.

A neutral background is a necessary precondition to perform a correct color calibration. The BackgroundNeutralization tool can be applied prior to ColorCalibration or other color calibration tools and procedures.

BackgroundNeutralization requires a good background reference. A good background reference includes mainly data that actually represents the sky background in the target image.

From Color Calibration:

The ColorCalibration tool performs a balancing of the colors of a linear RGB deep-sky image based on the following documentary criteria:

Maximize information representation in the calibrated color image.
Don't favor any particular color or spectral type as a white reference.
Note that this is a spectrum-agnostic color calibration procedure, very different from other methods based on fixing a white reference with respect to a particular spectral type.

Our approach originates from the fact that —in our opinion— the concept of real color makes no sense in deep-sky astrophotography. Real color doesn't exist in the deep sky because, on one hand, the objects represented in a deep-sky image are far beyond the capabilities of the human vision system, and on the other hand, the physical nature, properties and conditions of the deep-sky objects are very different from those of the subjects that can be acquired under normal daylight conditions.

This video and this video could be also of helps about the use of both tools.

Saludos, Alejandro.
 

[stevek]

 
Thankyou guys!  I have got it at last! Never realized that!
Many regards, Steve

[RickS]

Both processes log some details on the process console so you can see what effect they had.