What is neutral density filtervs ndfilter

NOTE: Do not place ND filters in series with their surfaces parallel. Parallel surfaces may cause multiple internal surface reflections which can combine to cause an increase in transmittance; this is especially true of the metallic type filters.

Neutral density filterOphthalmology

Neutral Density filters can be stacked in series to produce higher densities. The total optical density is the sum of the individual densities. The total transmittance of a stack of neutral density filters is the product of the transmittance of each filter.

Solid glass absorptive ND filters are relatively neutral in the 400 to 700 nm range. They are usable from 350 nm to 2500 nm, but the transmittance is different from that expected from the density value. Since most of the incident energy is absorbed, there filters produce fewer problems from multiple reflected beams comparing to the metallic type, but they are intended only for use with lower power sources.

Neutral density (ND) filters are used to equally attenuate the intensity of a light beam over a wide wavelength range. ND filters range from colorless to gray in appearance. Metallic neutral density filters provide a relatively consistent degree of attenuation over a wide spectral band. We offer a variety of catalog ND filters for UV/VIS applications including absorptive, metallic on glass or fused-silica, and variable linear or circular, as well as filters for infrared applications.

What is neutral density filterused for

Neutral density filterchart

The metallic ND filters use a thin coating of inconel on a glass or fused silica substrate. The inconel material contains a number of different elements such as nickel (Ni), chromium (Cr), cobalt (Co), and iron (Fe). Careful control of the alloy composition and vacuum deposition produces coatings which are spectral neutral over a wide wavelength range. The metallic ND filters are generally more neutral comparing to the absorptive type of ND filters. UV Fused silica substrate are useful in the ultraviolet spectrum, while the cost effective B 270 optical glass substrate provides excellent performance in the visible and Near-IR spectrum range. Always use these filters with the reflective side facing the radiation source. The metallic ND filters withstand higher power and thermal shock better comparing to the absorptive type. These filters are spectrally neutral beyond 2 µm.

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Optical Density (OD) is defined as the logarithm to the base ten of the ratio of the power of the incident beam to that of the exiting beam. The optical density can be convert to transmittance using the following equations:

These ND filters attenuate by absorption (and Fresnel reflection, the constant reflection from the air-glass interfaces). The absorption is iconic in anature so this type of density filter follows the Beer and Bouguer"s Laws.

Shop and browse all of our standard Neutral Density Filter models, or select a product series below for more information on our products and capabilities.