Neutral Density (ND) filters can reduce the intensity of light equally without appreciably changing its color. fader ND filter can change the luminous flux substantially with freedom, reducing the amount of light from 2 times of the lowest to about 400 times of the hightest. It can easily replace dozens of all grades of density ND gray filters (max. equal to 3 ND9)(1 ND9 can reduce three grade light). The operation is extremely convenient when selecting your desired density, just rotating filters. The index marks on the filter let you know exactly the amount of reduction at a glance.This ND filter is highly recommended by famous photographers and film directors. If you have it, you won't need to carry a bunch of filters for shooting. Features: This ND filter is much thinner than that of other brands, two filters fits each other better. It is adjustable from ND2, ND4, ND8 to ND400 infinitely, satisfied different shooting conditions. Neutral Density (ND) filters can reduce the intensity of light equally without appreciably changing its color. Neutral density filters are often used to achieve motion blur effects with slowing shutter speeds. Mark scale and "Min"(the lightest), "Max" (darkest) tags on the outer ring to help users accurately resets to a certain density. In a strong light environment, to shoot the scene of small depth of field (blur the background, thus showing the main body). In a bright environment, using high-density photography to shoot the scene of dynamic objects. In a bright environment, to shoot strong dynamic screen (such as streams, waves, athletes, wind and vegetation, etc), we often use a longer shutter time, to blur the whole movement or a part. Modulate to the appropriate density for flash photography at close distance. Used in variety of the scenes which need a wide range of adjusting the amount of light. With 49mm male thread/ 52mm female thread, can be mounted to 49mm lens or attached to 52mm additional filter. Fits SLR camera/ digital camera/ camcorder DV. Specifications: Material: Optical Glass Neutral density grade: 2-400 Back thread diameter (attach to lens, male thread): 49mm Front thread diameter (attach to additional filter, female thread): 52mm Item weight: 18.5g / 0.65oz Package size: 7 * 8.5 * 1.4cm / 2.76 * 3.35 * 0.55in Package weight: 44g / 1.55oz Package List: 1 * 49mm Fader ND Filter