This Technical Farm lens flare adapter is all about light leaks
At the 2015 Interbee show the Japanese company Technical Farm had on display a new "lens flare adapter" prototype that intentionally leaks light in order to create flare effects. Pricing and shipping dates were not announced. The flare adapter will be available in PL to E-mount, EF to E-mount and EF to EF versions. Additional information:
"It’s called a Flare Adapter and is designed to sit between the lens and the camera sensor, allowing outside light to pass through. This means you can create more controllable flaring effects that may be useful for certain types of projects. You can limit how much light passes through it by placing your fingers over the adapter or using gaffer tape to block parts off."
Via Newsshooter