Reddit reviews Hoya 52mm R-72 Infrared Filter

For what it's worth you can buy filters for your DSLR that remove all the visible light and only expose IR light to the CCD. Then you can do IR photography and take pictures like these.

The problem is you are now filtering out most of the visible light and the filter covering the camera's CCD is filtering out most of the IR light so you are left with very long shutter speeds. The solution is to modify your DSLR and take out the filter that covers the CCD. Hard-core IR photographers will do exactly this and then they can do much faster photography in the IR spectrum. Of course, now your camera is gonna take weird normal photos so you better make the mod to an older camera you don't care about...

PS: A lot of webcams "night vision" modes are just a bunch of IR LED's (the kind you'd see in a remote except much brigher) that illuminate the darkly lit room... You can't see the LED's cause your eye doesn't do IR but the CCD on the webcam sure as hell can...