Here is one good tip to convert some picture into a B/W colors.
Sometimes black and white pictures are too flat. This problem is a result of conversion of colors with same lightness into a black with same tint. For example, in RGB picture Red 200 and Blue 200 will become all Black 200.
This tip will give you possibility to choose a depth of the BW picture.
First open the picture and create a adjustment layer Hue/Saturation. Click OK without any changes.
Set this Hue/Saturation Layer to Color
from blending options (there is still no visible changes on picture).
Make another Hue/Saturation layer and set the Saturation (-100) and click OK.
Now the good part. Click double on the first Hue/Saturation layer
and move the Hue
slider. When you move the Hue slider the colors of picture are changing and the depth become different.