When cropping an image in CS6 or newer, you can see the final result by matching the Crop Shield’s overlay color to the canvas color.
To do so, create your crop border, then click on the Crop Options icon in the Options Bar, and increase the Crop Shield Opacity to 100 percent, and set the Color to Match Canvas. This will cover the crop area with your canvas color, and will allow you to see what the final crop will look like.