Neutral Density Filters

KUPO Optics' Neutral Density Filters are a testament to optical excellence, offering an essential solution for professionals in photography, microscopy, and machine vision. These precision-engineered filters uniformly reduce the intensity of visible light across the spectrum without altering the color balance, thus preserving the vividness and authenticity of images. The range, labeled from NDF-001 to NDF-004, caters to diverse lighting conditions, with each filter providing a specific level of light attenuation to suit various photographic and observational needs.
Constructed from high-quality borosilicate glass (D263T), these filters not only offer remarkable optical properties but also boast exceptional heat resistance, enduring temperatures up to 450℃. This resilience makes them ideal for use in environments with intense lighting, where standard filters might degrade. Their spectral tolerance within the visible wavelength region (400-700nm) maintains a tight accuracy of +/- 3%, ensuring consistent performance. The ND Filters' ability to control exposure without impacting shutter speed or aperture settings is invaluable in capturing the perfect shot in photography, or obtaining clear, detailed imagery in photomicrography and machine vision applications.
KUPO's commitment to quality is evident in the meticulous production of each filter, ensuring perfect piece-to-piece and batch-to-batch consistency. Adhering to the MIL-M-13508C standards for humidity, adhesion, and abrasion, these Neutral Density Filters are not just tools but enduring investments in professional imaging and research. Their specialized function focuses on managing light intensity with precision, making them an indispensable asset in the toolkit of photographers, scientists, and industrial vision experts. 

The Applications of Neutral Density Filters

Neutral Density (ND) filters are optical filters designed to uniformly reduce the amount of light entering a lens without altering the hue or color rendition. By attenuating the light intensity, these filters enable control over exposure times and aperture settings, affording wide-ranging applications in photography, cinematography, laser systems, machine vision, and stage lighting. ND filters are crucial tools for managing light exposure, enhancing image quality, and ensuring the consistent performance of optical instruments.
Photography and Cinematography
In photography and cinematography, ND filters are used to prevent overexposure in bright environments. They allow photographers and filmmakers to maintain their desired depth of field and shutter speeds without compromising on the quality of the captured image. For instance, an ND filter can enable the use of a wide aperture for a shallow depth of field, even under the bright sunlight. In video production, ND filters help maintain a constant frame rate while adjusting to varying lighting conditions, ensuring smooth visual storytelling.
Machine Vision
ND filters are utilized in machine vision to maintain the contrast and resolution of images under varying light intensities. By controlling the light that reaches the sensors, these filters prevent the over-saturation of images and help the system accurately detect edges, patterns, and objects. ND filters are particularly valuable in high-speed imaging or when capturing images of very bright objects, ensuring the vision system operates optimally regardless of fluctuations in ambient lighting.
Stage Lighting
In the context of stage lighting, ND filters serve to balance the brightness across different parts of the stage, allowing for better control over the visual ambiance of a performance. They can be used to reduce the intensity of spotlights or to even out the lighting for a more harmonious aesthetic effect. This is beneficial for live performances or broadcasts, where subtle lighting nuances may be critical for achieving the desired production quality.
Laser Systems
ND filters are essential components in laser systems for adjusting the power density of a laser beam before it interacts with a target material or surface. This is particularly important in applications like laser cutting, engraving, or welding, where precise control over the laser intensity dictates the quality and accuracy of the process. In laser safety and medical applications, ND filters can help reduce the beam intensity to protect sensitive instruments and human eyes from damage.
Optical Instrumentation
Various optical and scientific instruments employ ND filters to control the intensity of light without influencing other variables in an experimental setup. In optical microscopy, for example, ND filters can be crucial in obtaining the correct image exposure, which is particularly important when capturing images of live cells or dynamic reactions. Similarly, in spectrophotometry, they ensure that the detectors are not saturated by intense light sources, allowing for accurate spectral measurements.
In astronomy, ND filters are used to view and image celestial phenomena, such as solar eclipses or the surface of the moon, by reducing the overall brightness without affecting the coloration. Astronomers and astrophotographers use ND filters to protect their equipment and to capture detailed observations of bright objects without overexposing the image.
In summary, neutral density filters have a wealth of applications across numerous fields where light modulation is needed. By providing precise control over exposure, ND filters are vital for enhancing image capture, ensuring consistency in vision systems, managing stage aesthetics, performing accurate measurements, and protecting sensitive equipment and eyesight. Their versatility and usefulness are testament to their essential role in industries that rely on precise light manipulation.
KUPO Dichroic/ Neutral Density Filters


● Perfect piece-to-piece, batch-to-batch consistency
● Evenly reducing the intensity of visible light

Examples of Applications

● Photography
● Photomicrography
● Machine Vision

Borosilicate Glass (D263T)

● Thickness: 0.21mm, 0.3mm, 0.55mm
● Heat Resistance: Up to 450℃

General Specification

● Spectral Tolerance: 400~700nm Tavg +/- 3%
● Available Substrate: See Glass Substrates under Products Page
● Humidity, Adhesion, and Abrasion: MIL-M-13508C


KUPO Dichroic/ Neutral Density Filters / NDF-001
Reference color #LEE 209
400~700nm Tavg = 40% +/- 3%
KUPO Dichroic/ Neutral Density Filters / NDF-001


KUPO Dichroic/ Neutral Density Filters / NDF-002
Reference color #LEE 210
400~700nm Tavg = 20% +/- 3%
KUPO Dichroic/ Neutral Density Filters / NDF-002


KUPO Dichroic/ Neutral Density Filters / NDF-003
Reference color #LEE 211
400~700nm Tavg = 6.5% +/- 1.5%
KUPO Dichroic/ Neutral Density Filters / NDF-003


KUPO Dichroic/ Neutral Density Filters / NDF-004
Reference color #LEE 299
400~700nm Tavg = 2.5% +/- 1%
KUPO Dichroic/ Neutral Density Filters / NDF-004