Hello
I'm relatively new to Pixinsight but I'm slowly working my way through the many different functions. One function that I'm having difficulty with is understanding is the CurvesTransformation tool. Specifically, I'd like to work in the LAB colour space to increase the colour saturation of my images. The reason I wish to do this in the LAB colour space, is because it was designed to the perceptively uniform for human vision.
Unfortunately, I cannot see how to achieve this without impacting the colour balance of the image. For instance, say I take an RGB image and use the CurvesTransformation tool. I select the "a" channel in the LAB space by clicking on "a" channel button. If I now modify the "a" channel by first clicking on the point 0.5, 0.5 and I pull down on the lower curve portion I will create a symmetric "S" shaped curve. If I now apply the result to the RGB image, the saturation of the reds are increased but the colour balance of the image has changed. I don't understand this behavior since the CurvesTransformation document states that the "The CIE a* chrominance component corresponds to the red/green ratio" - so if I create a symmetric "S" curve on the a channel then why does it introduce a colour imbalance ?
I should point out that increasing colour saturation in non LAB space work as expected - eg clicking on the CurvesTransformation "S" button (saturation) and modifying the curve changes the saturation without introducing a colour imblance. I'm also aware of the ColorSaturation tool, which works as expected - eg colour imbalance is again not created.
So, can someone please explain to me how you increase colour saturation in the LAB space without impacting the colour balance of the image ?
Alan
