Neutral Density (ND) Filters are generally gray in transmission, reduce light intensity equally over a specified wavelength range and result in no change to image color or contrast. MidOpt offers two types of Neutral Density Filters: “ND” series filters that use absorptive filter glass, and “Ni” series filters which partially reflect a portion of the light entering the lens.
MidOpt Neutral Density Filters (ND) are defined according to their optical density (OD). For example, ND060 is an ND Filter with an OD of 0.60. The higher the OD, the lower the transmission.
MidOpt ND Filters have male and female threading, so they can easily be stacked to test various optical densities. For example, an ND030 Filter, which has an OD of 0.3, mounted together with an ND120 Filter, which has an OD of 1.2, will result in an ND150 Filter, which has an OD of 1.5.
LIGHT SATURATION REDUCTION
When an item being inspected is surrounded by an unmanageable amount of light, using a Neutral Density Filter (ND) may be the only way to image the item.
Opening the lens aperture creates a shallower depth of field but lets in more light. ND Filters allow for larger apertures to be used, while limiting overexposure by attenuating incoming light.
MidOpt® ND Series Neutral Density Filters
| Description: | Useful Range: | Optical Density: | |
 | ND030 Neutral Density Filter - Absorptive 50% Transmission | 425-675nm | 0.3 |
 | ND060 Neutral Density Filter - Absorptive 25% Transmission | 425-675nm | 0.6 |
 | ND090 Neutral Density Filter - Absorptive 12.5% Transmission | 425-675nm | 0.9 |
 | ND120 Neutral Density Filter - Absorptive 6.25% Transmission | 425-675nm | 1.2 |
 | ND200 Neutral Density Filter - Absorptive 1.0% Transmission | 425-675nm | 2.0 |
 | ND300 Neutral Density Filter - Absorptive 0.1% Transmission | 425-675nm | 3.0 |
 | ND400 Neutral Density Filter - Absorptive 0.01% Transmission | 425-675nm | 4.0 |
MidOpt® Ni Series Neutral Density Filters
| Description: | Useful Range: | Optical Density: | |
| Ni030 Neutral Density Filter - Low Reflectivity 50% Transmission | 400-2000nm | 0.3 |
| Ni060 Neutral Density Filter - Low Reflectivity 25% Transmission | 400-2000nm | 0.6 |
| Ni090 Neutral Density Filter - Low Reflectivity 12.5% Transmission | 400-2000nm | 0.9 |
| Ni120 Neutral Density Filter - Low Reflectivity 6.25% Transmission | 400-2000nm | 1.2 |
| Ni200 Neutral Density Filter - Reflective 1% Transmission | 400-2000nm | 2.0 |