trash and the sky

There is a very cool thing you can do if your want to play with lighing of different colors. Take a shot outside at dusk or dawn. It should be so light/dark that the flash would be needed for correct exposure. Now, cover the flash with some colored filter/piece of plastic. The light falling on you will now get mis-colored by the flash, while the background will not be. Now, in a photo program you correct the mis-colored skin, but this will in turn tweak the colors of everything else. Using this technique and making the flash yellow, you compensate by boosting the blue in the picture. This will give the background an extremely unnatural/intense blue colour, which can be very suggestive for e.g. a sky (like the one on this image). Try this with different colors. It's really cool.