Photographing solar eclipses and ultra-bright light sources can be extremely dangerous. This filter reduces light values by 9 stops to less than 1/500th of its original intensity and allows safe photography. It can also be used to achieve super slow shutter speeds in daylight to render moving subjects invisible..
HMC (Hoya Multi Coating) versions have 3 layers of anti-reflective coating on each surface which reduce reflections down to 1-2%.
For Long Exposure Photography the Tiffen APEX 10-stop filters incorporate an infrared hot mirror and IR blocker and is our recommended filter for doing long exposures on Digital SLR cameras.