Create Analog Lens Flares on a DSLR with 'Lens Whacking'
Now that everyone is shooting digital (at least on the low end), it takes a few tricks to achieve an analog look. Beyond adding film grain and burnouts in post, one way to do this is to slightly detach your DSLR's lens and let in a bit of outside light during your shot. Thus the term "lens whacking," i.e. letting light in from the sides and creating lens flares the analog way. Don't literally whack your lens -- but through subtle manipulation you can allow light to refract through the rear lens elements, giving you some interesting-looking flares:
More videos and details on the process over at planet5D.
Link: Lens Wacking - planet5D