There are many ways you will read about to convert a colour digital image to Black and White, there is the lazy way of just performing a de-saturation or just selecting Mode and Greyscale, I use a method called the Lab technique, there are several steps to perform, but I feel that I have more control over the final image.
First step is to open up your colour image in Photoshop, open up the path dialog, Window > Paths
Convert the image to Lab Color, Menu > Image > Lab Color
Now just select the lightness channel
Convert the image to Greyscale, Menu > Image > Greyscale
Convert the image to RGB Color, Menu > Image > RGB Color
Now we need to duplicate the layer, Layers > Duplicate
Choose Channels on the Paths dialog and select Multiply
Next Change the Opacity to 50%
Now create a new adjustment layer for channels, Layer > New Adjustment Layer > Channel Mixer
On the dialog check the Monochrome box and adjust the color sliders until you are happy with the image
Now you can do any other adjustments and save with a new name
