Circle Pattern

1. Create a new document (Ctrl+N). Choose the size of the squares you want in your grid. Here I'm using 25x25, make sure your width and height dimensions are the same, they have to be squares. Very important: don't forget to make your new document transparent. Otherwise nothing will be show behind the grid. And we wouldn't want that to happen do we..

2. Create a new layer (Ctrl+Shift+N) and grab the Elliptical Marquee Tool. Hold down shift and draw a circle, I made mine 20x20. Then fill it with a color of your choice (Alt+Backspace)

Select everything on the new layer (Ctrl+A) and go to Layer > Align Selection > Vertical Centers and then Layer > Align Selection > Horizontal Centers, now your circle is perfectly centered

3. Go to Edit > Define Pattern. You will see a window appear where you have to give your pattern a name. Just as the scanlines and grid pattern (see tutorials), it wil be saved in the library so you can use it again in the future

4. Now it's time to see your pattern in action. Create a new document (or open an image) and create a new layer (Shift+Ctrl+N). Fill it with your pattern by clicking Edit > Fill. Select your Circle Pattern and hit OK

5. The pattern might be a little overwhelming when you use it on an image, so bring down the opacity and or fill in the layers palette so you end up with a better result. Don't be afraid to really bring it down with more than 50 %. You don't want the pattern to take over your whole image