In order to add a nice contrast punch to an image using Photoshop, go to your adjustment layer and click on the black and white adjustment layer. Then go to your "blend modes" and change it to "overlay". If you find that the effect is too harsh you can adjust your opacity settings or you can switch your blend mode to "soft lights". In "overlay" using the black and white adjustment panel you can change your settings to meet your preference. If you are using a previous version of Photoshop that does not have a black and white adjustment layer, simply duplicate your layer by dragging it down to the new layer icon. Then go up to "image", "adjustments", "desaturate" and change your blend mode from there and you get the same effect.