I usually do droste effects with special software, but this time I decided to do it with Pixelmator.
The droste effect is interesting, and actually quite simple to do. You take part of a photo, and repeat it, over and over, giving the appearance of infinite repetition.
Here is the original photo. I asked my son, Tim, to hold a piece of colored cardboard, and took the shot.
I used Pixelmator's Paint Selection Tool and Magic Wand Tool to select the cardboard, and then used Edit->Refine Selection... to expand the selection by 1 pixel, and feather it slightly.
Then, I used the Eraser Tool to erase the cardboard, leaving a transparent hole in the photo.
I duplicated the photo, and then shrank and rotated the bottom layer, so it fit into the hole in the top layer.
I merged the two layers, which left me with a new picture with my first recursion, which of course had a smaller hole in it.
Then, I just repeated the process a couple of times: Duplicate, shrink, rotate, merge...
I exported the resulting photo, imported it into Aperture, and gave it a final touch, increasing definition, brightening it, and increasing the saturation just a touch.
Easy to do, and fun.