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2.5 OD Absorptive Glass ND Filter 12.5mmdia x 2.4mmthk

SKU: FNG2513
More Information
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Diameter (mm) 12.5
Thickness (mm) 2.4
Type Absorptive Glass ND Filter
Density @ 546nm 2.5
Material/Equivalent NG3
Transmission (%) @ 546nm 0.32

Glass Neutral Density filters attenuate light by absorption just like the gelatine neutral density filters. Glass ND Filters are more robust and tend to have more uniform absorption characteristics. They also attenuate by absorption and so care must be taken to avoid overheating. Attenuation is achieved by polishing glass to the correct thickness.

Knight Optical offers stock absorptive ND filters in 12.5mm and 25mm diameters, and 50x50mm squares manufactured from high quality glass. Each filter is available with blocking between 0.1 and 4.0 OD and are available to purchase direct from this page.

In addition to our stock absorptive glass ND filters, Knight Optical also offers an extensive custom optic service thanks to our many years of experience in the industry. We are able to supply ND filters cut to sizes and shapes to fit individual application and mount filters where applicable. For more information on our custom glass ND filters, or for more information on our entire filter range, contact our technical sales team.

Optical Density:
Surface Quality:
Colour Glass
± 12.5% (@546nm)
+0/-0.2 mm
±0.2 mm
Varies between batches to control the OD
<60-40 scratch/dig

Mounting of diameters and squares.
Antireflective coatings can be applied to one or both faces for improved transmission.
Cutting down or edged to special shapes and sizes at short notice.
Available in sets, supplied in a wooden storage box for research and laboratory use.