MECO Neutral Density Filter. The following models of ND filters are listed by the number of aperture stops and the amount of light reduced during a specific time. A larger number means a lower amount of light and a lower light density. Note: ND filters on the market are by no means perfect. And they may not reduce the density of light of all wavelengths equally, which can lead to color cast of pictures, especially with inexpensive filters. More importantly, most ND filters are specified only over the visible region of the spectrum, and do not block proportionally all wavelengths of far infrared rays and ultraviolet rays. Thus using an ND filter to adhere to these ray sources such as the sun, incandescent metal or glass can be dangerous. These sources emit intense non-visible radiation that can damage the eyes, Even if they don't look bright when viewed through the filter. Special filters must be used if such sources are viewed safely. Typical uses of the ND filter include the following: Blurring water motion (such as waterfalls, rivers and oceans) Reduces depth of field in very bright light (such as daylight) Reducing the visibility of moving objects Adding motion blur to subjects ND Filter It is also used on catadiopic telescope cameras, which have no aperture device that seriously affects WAN imaging quality.
