When you send images for print you need to check them for flaws that might not be visible when viewed on a screen. Typical flaws include sensor dust, uneven gradients, and healing/clone problems.
A simple and very effective way is to use what is often referred to as a solar curve adjustment layer.
As you can see in the image above, this technique will complete distort your image and expose any flaws.
You can download an action that I have created from here:
Solar Curve | connywallstrom.zip