Creating a Black and White Conversion in Photoshop isn't as easy as clicking a button. You should NEVER just click 'desaturate' or 'grayscale'-- you are loosing a lot of creative control and quality by choosing these options. Instead, you should use the black and white conversion tool offered in Photoshop C3 (and newer). It is an amazing tool that gives you complete control over the black and white conversion and how each tonality is represented in grayscale. This video tutorial gives tips on conversion, including conversions specifically for portraiture.
In this tutorial Lindsay Adler will teach you how to do exquisite black and white conversions in Photoshop (cs3 and newer). Using the black and white adjustment layer tool, photographers are given complete control and simplicity for converting images to black and white. Lindsay will introduce you to the power of this tool and provide several tips on making conversions.
Adler Photo Workshops