Bespoke Ordering Available
Knight Optical offers a comprehensive range of neutral density filters (ND filters), designed to reduce light transmission across a specified waveband or wavelength with consistent attenuation, either by absorption or reflection.
Our ND filter portfolio includes:
- Absorptive filter glass that reduces light through absorption, utilising Schott (or equivalent) filter glass, polished to achieve the desired optical density (OD) at specific wavelengths or ranges. These filters are robust and not affected by the angle of incidence but require attention to avoid overheating.
- Metallic ND filters, created by depositing a thin metallic layer onto standard glass materials like borosilicate or UV fused silica. These filters attenuate light via reflection, mitigating the overheating risks associated with absorptive filters.
- Wratten ND filters offer an economical alternative, absorbing light similar to ND filter glass but with more wavelength fluctuations and a narrower effective wavelength range.
Our stock catalogue includes a variety of ND filters ready for order, with dimensions such as 12.5mm and 25mm diameters, and 50x50mm squares. These can be further customised to smaller sizes upon request.
For those looking for specific applications, such as 82mm ND filters, PolarPro ND filters, Freewell ND filters, NiSi ND filters, and more, we invite custom orders to meet your precise needs. While we excel in fixed ND filters, including options like 82mm variable ND filters, GoPro ND filters, ND filter for Canon, K&F ND filters, and iPhone ND filters, please note that currently, Knight Optical does not offer variable or graduated ND filters.
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Metrology Testing and Quality Assurance
Our commitment to quality assurance means all filters undergo rigorous testing in our metrology lab, equipped with state-of-the-art Agilent Cary Spectrophotometers to measure transmission and absorption. Test data, including .CSV and ASCII files detailing spectral properties, is available upon request.
Frequently Asked Questions
What is a neutral density (ND) filter and how is it used?
A neutral density (ND) filter is a camera accessory that reduces the intensity of all wavelengths or colors of light equally, without altering the hue or color balance. It’s like sunglasses for your camera, allowing for slower shutter speeds, wider apertures, or lower ISO settings in bright conditions. This makes ND filters ideal for capturing motion blur in waterfalls, reducing depth of field in bright light, or preventing overexposure in video shooting.
How does a variable ND filter differ from a fixed ND filter?
A variable ND filter consists of two polarizing layers that, when rotated, adjust the amount of light passing through, offering a range of light reduction levels within one filter. This flexibility allows photographers and videographers to quickly adjust for changing light conditions without swapping filters. Fixed ND filters, on the other hand, reduce light by a specific amount, requiring you to change filters for different levels of light reduction.
What should I look for in the best variable ND filter for my camera?
When looking for the best variable ND filter, consider factors like optical quality to ensure minimal image degradation, the range of light reduction it offers (measured in stops), and the size compatibility with your lens. Additionally, look for features like low color cast, minimal vignetting, and ease of use. Reading reviews and comparing brands like Polarpro, Freewell, and NiSi can help determine which filter meets your needs.
Why would I need an 82mm ND filter, and what are its benefits?
An 82mm ND filter is needed if your camera lens has an 82mm diameter thread. This size allows you to control the amount of light entering the lens, enabling longer exposure times and wider apertures even in bright daylight. It’s beneficial for creating motion blur effects, such as smooth water or cloud movement, and for video recording to maintain a cinematic frame rate and depth of field.
Can ND filters be used on action cameras like GoPro or smartphones like the iPhone?
Yes, ND filters are available for action cameras like GoPro and smartphones like the iPhone. These filters can enhance the quality of photos and videos by controlling exposure and reducing shutter speed for smoother motion blur and reduced jello effect in video. Brands like GoPro and third-party manufacturers offer ND filters specifically designed to fit these devices, improving the versatility of action cameras and smartphones in various lighting conditions.
How do I choose the right ND filter for my Canon camera, and are there specific brands to consider?
Choosing the right ND filter for your Canon camera involves considering the lens thread size (e.g., 82mm) and the desired effect (e.g., number of stops). Brands like Polarpro, K&F, and NiSi are reputable and offer high-quality filters that cater to different needs, from fixed ND filters for specific light reduction to variable ND filters for flexibility. Ensure the filter matches your lens’s diameter and look for features like anti-reflective coating and water resistance for durability and improved image quality.
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With our in-house state-of-the-art metrology laboratory you can be confident that your optical components will meet your requirements. You can find out more about our testing facilities here.
Operating for over 30 years
Knight Optical has been operating for over 30 years, with our managing director Colin Overton at the helm. Over this time, we have become a global leader in the production and distribution of scientific optical components and bringing quality into focus for all of our products and services that we provide.