Filters from this product family may be used individually, or combined in series, to obtain any desired density from 0 to 7 in steps of 0.1OD. Please note that stacking an excessive number of filters may lead to numerous unwanted back reflections. All filters are shipped with a transmission curve.

The FB-ND Optical Crown Glass Metallic Neutral Density Filter Set is a set of eight 25.4 mm diameter optical crown glass metallic ND filters of OD 0.04, 0.1, 0.3, 0.5, 1.0, 2,0 and 3.0, which includes a wood case. Our metallic neutral density coatings provide broadband attenuation for low power applications. The coating is deposited on one side of a cost-effective B 270 optical glass substrate, providing excellent performance in the visible and NIR. Filter kits provide convenience and cost savings. All filters are shipped with a transmission curve.

Optical density (OD) is given by the relationship: OD = -log(T) or T = 10^(-OD) where T is transmittance (0≤T≤1). Optical Density, unlike transmittance, is additive. When multiple filters are stacked, the total density is easily found by adding up the densities of each filter in the series. For example to achieve desired transmittance of 8%, first calculate the equivalent density (OD = -log(0.08) = 1.097 ≅ 1.1), then find a combination of filters that adds to the desired number, such as a combination of an OD1 filter and an OD0.1 filter.

To prevent unwanted interference from etalon effects, filters should be angled slightly with respect to the incident beam. To minimize back reflections, the filter should be oriented with the coated metallic surface facing the incident beam. Any light reflected from the uncoated second surface will pass through the metallic coating first, which will greatly attenuate unwanted back reflections.