Just learned this fix for images that are too light and lack contrast. If you have a later version of Photoshop click on Control/Alt/2 (If that doesn't work because you have an earlier version, try Control/Alt/~ (tilde) and this will highlight the light areas. Then you can either Control-J to add the selection to a new layer and use Multiply blend mode to darken the light areas, or you can make a levels adjustment. (No doubt a Curves adjustment too!) On keyboard, the tilde (~) is found to the left of the number 1. I may have overdone this one just a bit!