Converting from RGB to LAB Color Space to Reduce Colors In many papers I see the following:


  First we have to convert image from RGB to LAB color space to reduce colors then algorithm can run faster.


I can't understand this. How can this happen? What I read is that Lab color space has support for more colors than the other. But I see people says converting to Lab reduces the colors to better calculation. Why and how does this happen?
You should read about LAB Color Space.

Its main advantage on RGB is by having 1 channel dedicated to the Luminosity of the Image and 2 others dedicated to the color information.

This means if you need to process only Luminosity / Color you can do that using LAB without having any effect on Color / Luminosity.