Photo mosaic overlays are a very cool effect that can be a great way to tie a set of images together around a main photo. Traditionally, they're quite a bit of work to make, but this awesome tutorial will show you a shortcut to creating them using Lightroom and Photoshop.
Coming to you from Phlearn, this helpful video will show you how to create a photo mosaic overlay using Lightroom and Photoshop. The effect can be really stunning: imagine taking all the delivered photos from a wedding and creating an overlay on a shot of the bride and groom or the like. Instead of building it from scratch, though, which would be very time-consuming, the trick is to do a little math to determine the correct dimensions, then use Photoshop's built-in contact sheet feature to make the mosaic. From there, you'll define it as a pattern that can be then stretched or compressed to fit whatever image you'd like to apply it to. After that, it's simply a bit of blending mode changes and adjustment layers to alter the effect to taste and you're done! It's a fun and different effect that doesn't take much effort, so grab a set of images and give it a try!