We're all familiar with vintage-style camera effects thanks to popular apps like Instagram, but applying those modifications after you take the image doesn't look as authentic and can hurt the image quality. Instead, you can create true light leaks and special effect colour with a plastic sandwich bag and a coloured marker.
DIY Photography explains:
Take two plastic sandwich baggies, colour one with a marker some bright colour like pink or purple and leave the other clear.
On the opposite end as the zip-lock (the closed end) rip it, tear it or cut it in some uneven fashion so that it is now open on both ends.
Wrap the zip-lock end around your camera lens leaving the torn end overlapping the lens a little bit. Most of us are holding the lens while we shoot so now you are holding the plastic bag on the lens with your hand.
Now manipulate the bag as you shoot so the centre of the lens is unobstructed and have fun!
The image above demonstrates how this all should look when you're done, plus one sample photo created with this nifty DIY trick. To see more awesome examples, check out the full post over at DIY Photography.