I stumbled upon lens whacking while spying the inter-web for the new Black Magic camera. Lens whacking is such an awesome technique to add flares and light leak to your videos. What is lens whacking? Lens whacking is filming with a 50mm lens or lower not attached to the camera body. As you're filming you shift your lens in various angles allowing light to hit the sensor. This is a great way to add flares manually without doing it in post. I prefer this technique because the video feels very dreamy and the light leaks are consistent with the light source on location.