Anyone can desaturate a color photo to produce the effect seen at left. However, there is a way to make a color image look as if it were taken in black & white. Follow along...

Layer > Adjustment Layer > Gradient Map. The default setting should work well, however, feel free to experiment.

It looks more natural already. However, we have one more step to complete.

Layer > Adjustment Layer > Brightness/Contrast. Use of setting of "7" on both.

The final result looks much more realistic. And almost as if you took the photograph with black and white film...