They are best used with Photoshop Blend Modes. Try different modes, layer them, change colors, etc. They are a very cool way to take your art to the next level.
Don't have Photoshop? That's ok. You can use these as backgrounds. Simply place them over a solid white page and bam! You have a new background. You can layer them too.
This kit includes:
60 light leaks and vignettes
300 dpi .jpg backgrounds/papers