The popularity of Apps for post processing photo's can easily be seen in the very number of options to those who use the iPhone as a creative tool. They give users a chance to change the look and feel of an image in a variety of different ways. While purists may say this is not photography, I say it is just another tool in our box to create our vision.
Still it is nice to experiment with other means of manipulation with out using apps. Those of us who have been taking photographs for years remember using filters of different types to give interesting looks directly on the film. Some of these techniques would be a challenge to create in post production using apps.
One of my favourite tricks is to shoot through different transparent medium. I have worked with glass bricks in the past and they can give a look of ripples on water. Today I tried something new, some Mylar that came with some glasses that the boys got with a book. Holding it over the lens of the iPhone I watched the way the light bounced around on the screen and then snapped when I got some patterns I liked. This one was the best, an almost kaleidoscope effect.
It is fun to continue to experiment with different techniques as it keeps photography fun and fresh.