So many times when you use a blur tool from Photoshop to your image and then throw on a gradient or two, you will get "banding" in your image. There is a way to minimize this, it doesn't always get rid of it completely though. First you have to create your pattern or noise pattern that you want to create. Lets start with a new document.
Make it about 80x80 pixels in size, in 8-bit RGB colour. Next go to Edit, choose Fill. Then, choose Filter -> noise -> add noise. ---> settings are: Amount - 5%, Distribution - Uniform You should see a little grey box now. Choose Edit - Define Pattern - Name it Noise, press OK.
After you have finished with your blur tool and gradient tool, add a new fill layer from your layer menu. Choose pattern. Set your blend mode to "Linear Light" and the Opacity to between 20-25%. Make sure the pattern you are choosing in the next step is the one you just created. Select OK.
Now paint the noise OFF your subject(s). Remember the noise is so small you won't think you have to, but if you zoom in, you will see how important it is to do this.
Use this tool if you want to create creamy smooth backgrounds without banding. It isn't prefect all the time, but will help a lot of the time!