Spec
Fixed ND (Neutral Density) Filters
Fixed ND Filters
Our absorptive neutral density (ND) filters are available in four sizes with optical densities (OD) ranging from 0.1 to 8.0. Unlike their reflective, metallic counterparts, each ND filter is fabricated from a Schott glass substrate that has been selected for its spectrally flat absorption coefficient in the visible region from 400 nm to 650 nm. By varying the type and thickness of the glass used, we are able to produce the entire line of absorptive ND filters from just four types of Schott glass. Due to the variations between different lots of glass, Thorlabs recommends that each filter be calibrated in the user’s setup before taking quantitative measurements. The Specs tab contains the typical transmission and damage threshold of each filter type, while the Graphs tab contains transmission and reflectivity curves for the 300 – 1100 nm wavelength range.
For each filter size option available, Thorlabs also offers a filter kit option at the bottom of this page. Each kit contains a selection of 10-12 of the most popular absorptive neutral density filters for that size. A lockable metal case with a foam insert for storing loose square filters is also available below.
| Model | Description | Transmission Data |
|---|---|---|
| NE01B | Unmounted Ø25 mm Absorptive ND Filter, Optical Density: 0.1 |  |
| NE02B | Unmounted Ø25 mm Absorptive ND Filter, Optical Density: 0.2 |  |
| NE03B | Unmounted Ø25 mm Absorptive ND Filter, Optical Density: 0.3 |  |
| NE04B | Unmounted Ø25 mm Absorptive ND Filter, Optical Density: 0.4 |  |
| NE05B | Unmounted Ø25 mm Absorptive ND Filter, Optical Density: 0.5 |  |
| NE06B | Unmounted Ø25 mm Absorptive ND Filter, Optical Density: 0.6 |  |
| NE07B | Unmounted Ø25 mm Absorptive ND Filter, Optical Density: 0.7 |  |
| NE08B | Unmounted Ø25 mm Absorptive ND Filter, Optical Density: 0.8 |  |
| NE09B | Unmounted Ø25 mm Absorptive ND Filter, Optical Density: 0.9 |  |
| NE10B | Unmounted Ø25 mm Absorptive ND Filter, Optical Density: 1.0 |  |
| NE13B | Unmounted Ø25 mm Absorptive ND Filter, Optical Density: 1.3 |  |
| NE15B | Unmounted Ø25 mm Absorptive ND Filter, Optical Density: 1.5 |  |
| NE20B | Unmounted Ø25 mm Absorptive ND Filter, Optical Density: 2.0 |  |
| NE30B | Unmounted Ø25 mm Absorptive ND Filter, Optical Density: 3.0 |  |
| NE40B | Unmounted Ø25 mm Absorptive ND Filter, Optical Density: 4.0 |  |
| NE50B | Unmounted Ø25 mm Absorptive ND Filter, Optical Density: 5.0 |  |
| NE60B | Unmounted Ø25 mm Absorptive ND Filter, Optical Density: 6.0 |  |
| NE70B | Unmounted Ø25 mm Absorptive ND Filter, Optical Density: 7.0 |  |
| NE80B | Unmounted Ø25 mm Absorptive ND Filter, Optical Density: 8.0 |  |
Variable ND (Neutral Density) Filters
Variable ND Filters
Thorlabs offers both continuously variable and step variable ND filters. Round filters are available unmounted or mounted. The mounted versions allow the appropriate optical density to be quickly set. The continuously variable round filters can also be purchased in a 30 mm cage-compatible version. Our rectangular variable ND filters are available in one of two sizes and a number of optical density ranges. Additionally, we offer an adjustable, absorptive ND filter in a post-mountable, 30 mm cage-compatible housing.
| Model | Description | Download |
|---|---|---|
| NDC-50S-1 | Unmounted Step Variable ND Filter, Ø50 mm, OD: 0.04-1.0 |  |
| NDC-50S-3 | Unmounted Step Variable ND Filter, Ø50 mm, OD: 0.04-3.0 | |
| NDC-100S-4 | Unmounted Step Variable ND Filter, Ø100 mm, OD: 0.04-4.0 | |
| NDC-50S-1M | Mounted Step Variable ND Filter, Ø2.5″, OD: 0.04-1.0 | |
| NDC-50S-3M | Mounted Step Variable ND Filter, Ø2.5″, OD: 0.04-3.0 | |
| NDC-100S-4M | Mounted Step Variable ND Filter, Ø4.5″, OD: 0.04-4.0 | |
| NDC-25C-2 | Unmounted Continuously Variable ND Filter, Ø25 mm, OD: 0.04 – 2.0 | |
| NDC-25C-4 | Unmounted Continuously Variable ND Filter, Ø25 mm, OD: 0.04 – 4.0 | |
| NDC-50C-2 | Unmounted Continuously Variable ND Filter, Ø50 mm, OD: 0.04 – 2.0 | |
| NDC-50C-4 | Unmounted Continuously Variable ND Filter, Ø50 mm, OD: 0.04 – 4.0 | |
| NDC-100C-2 | Unmounted Continuously Variable ND Filter, Ø100 mm, OD: 0.04 – 2.0 | |
| NDC-100C-4 | Unmounted Continuously Variable ND Filter, Ø100 mm, OD: 0.04 – 4.0 | |
| NDC-25C-2M | Mounted Continuously Variable ND Filter, Ø25 mm, OD: 0.04 – 2.0 | |
| NDC-25C-4M | Mounted Continuously Variable ND Filter, Ø25 mm, OD: 0.04 – 4.0 | |
| NDC-50C-2M | Mounted Continuously Variable ND Filter, Ø50 mm, OD: 0.04 – 2.0 | |
| NDC-50C-4M | Mounted Continuously Variable ND Filter, Ø50 mm, OD: 0.04 – 4.0 | |
| NDC-100C-2M | Mounted Continuously Variable ND Filter, Ø100 mm, OD: 0.04 – 2.0 | |
| NDC-100C-4M | Mounted Continuously Variable ND Filter, Ø100 mm, OD: 0.04 – 4.0 | |
| NDL-10S-2 | Step Variable ND Filter, 10 mm x 50 mm, OD: 0.3 – 2.0 | |
| NDL-10S-4 | Step Variable ND Filter, 10 mm x 50 mm, OD: 0.1 – 4.0 | |
| NDL-25S-2 | Step Variable ND Filter, 25 mm x 100 mm, OD: 0.3 – 2.0 | |
| NDL-25S-4 | Step Variable ND Filter, 25 mm x 100 mm, OD: 0.1 – 4.0 | |
| NDL-10C-2 | Continuously Variable ND Filter, 10 mm x 50 mm, OD: 0.04 – 2.0 | |
| NDL-10C-4 | Continuously Variable ND Filter, 10 mm x 50 mm, OD: 0.04 – 4.0 | |
| NDL-25C-2 | Continuously Variable ND Filter, 25 mm x 100 mm, OD: 0.04 – 2.0 | |
| NDL-25C-4 | Continuously Variable ND Filter, 25 mm x 100 mm, OD: 0.04 – 4.0 | |
