Okay, so these were not made with a Holga... but they were made with a digital camera and absolutely NO photoshop other than cropping and minor density change.
I saw this technique on Zack Arias's blog the other day, and figured I'd have to give it a try for myself... and this is the result. If I have some time, I will try to do a little writeup of the technique and take a photo of my contraption, but if you don't want to wait you can just head over to his blog and see how it was done!
