The Hoya variable density filter uses two polarization layers to control the amount of light that passes through the filter and into the camera lens. At least in its effect the filters let through 1/3 of the light of the scene. This corresponds to 1.5 f-stops or shutter speed values. At its maximum, the filter leaves only 1/400th of the light. This corresponds to 9 aperture or shutter speed values.
Once the filter is mounted on the lens, rotating the filter ring between ''Min'' and ''Max''' allows optimum control of the amount of light entering the lens. With the Hoya variable density filter it is possible to take pictures with open lenses such as a 50mm f/1.4 to f/1.4 in full sunlight to achieve a very low depth of field. Or to slow down the shutter speed to pause for a few seconds in full sunlight. This is enough to create artistic shots of movements that blur on water, cars, people, or almost anything that moves. The creative possibilities are unlimited.
Hoya ND's variable filter uses high-quality optical lenses from Hoya Corporation, the world's largest manufacturer of optical glass. It is available in diameters from 52mm to 82mm. For best results, it is recommended to use a tripod when shooting at slow shutter speeds.…more