I'm frequently using LAB color method in order to turn my images into monochrome. I first convert the file into LAB, then I dump a, b and alpha 2 channels, just preserving alpha 1 (i.e. luminosity). This way I avoid the hassle of some artifacts appearing, for instance, in blue sky areas when converting into monochrome via the usual Photoshop color mixer.
What amazes me in this process is the increase in overall sharpness of the converted image, especially in the details. My technical knowledge doesn't go far enough to understand why. So I'd be grateful to anyone explaining to PhotoGraphia readers and myself why a LAB-converted image is (or looks) sharper than an RGB unsaturated one.
Thank you in advance.