Glass Neutral density filters These Glass Neutral Density Filters are an inexpensive form of absorption density filter. They are made using the Schott range of NG glass types.  Neutral density filters attenuate light by absorption whilst achieving minimum reflection. The density of neutrality of the filters is achieved through selection of the filter type and calculation of the thickness. The optical density is reasonably consistent in the visible (400-600nm) but may be higher or lower in the NIR depending on glass type.
Knight Optical > Filters > Neutral density filters - Glass type > 25 diameter (mm) Only UK and EU customers are charged VAT at 17.5%, customers outside the EU and EU customers based outside the UK who have a valid EU VAT number will not be charged VAT Bulk Discounts! Where (B) appears next to a price below, bulk prices are available, click the (B) button to view! PDF Part No. Material Thickness (mm) Density @546nm Trans (%) @ 546nm Trans (%) @ 700nm Trans (%) @ 780nm Trans (%) @ 850nm Trans (%) @ 1060nm Trans (%) @ 1500nm Price Qty Buy FNG0125 NG11 0.6 0.1 79 80 78 75 69 77 £17.95 FNG0225 NG11 1.4 0.2 63 64 60 54 43 59 £17.95 FNG0325 NG11 2.3 0.3 50 52 46 39 27 44 £17.95 FNG0425 NG11 3.2 0.4 40 42 35 28 17 34 £17.95 FNG0525 NG11 4.1 0.5 32 33 27 20 11 26 £17.95 FNG0625 NG5 2.3 0.6 25 31 30 24 15 32 £17.95 FNG0825 NG5 3.1 0.8 16 21 20 15 8.2 22 £17.95 FNG1025 NG5 3.9 1 10 14 13 9.4 4.3 15 £17.95 FNG1525 NG4 2.9 1.5 3.2 5.3 6.7 4.6 2.7 11 £17.95 FNG2025 NG4 3.8 2 1 2 2.7 1.6 0.79 5.5 £17.95 FNG2525 NG3 2.4 2.5 0.32 1.4 2.5 2.5 1.2 9.8 £17.95 FNG3025 NG3 2.9 3 0.1 0.6 1.2 1.2 0.51 6.2 £17.95 FNG4025 NG3 3.9 4 0.01 0.11 0.29 0.29 0.087 2.5 £17.95 FNG9200 SET OF 13 Filters NA NA NA NA NA NA NA NA £219.00 Knight Optical > Filters > Neutral density filters - Glass type > 25 diameter (mm)
Specification   Material: Schott Colour Glass Optical Density : ± 12.5% (@546nm) Diameter: +0.0 / -0.2 mm Length / width: ± 0.2 mm Thickness: ± 0.1 mm Surface quality: <60-40 Flatness: <2.5λ over 90% test area Parallelism: <3 arcmin
Specific requirements We can manufacture Schott Colour-glass filters to any size at short notice, so if your requirements are not listed please contact us by telephone / fax or email: stockrequirement@knightoptical.co.uk Options available   · AR Coating   · Cutting down or edged to special shapes and sizes   · Mounting (circles) Technical Data Sheets Set of transmittance curves are available for each filter on request, please specify type. See also Metallic neutral density filters Gelatin neutral density filters See also FNG0400 12.5mm dia set (13 filters) FNG0200 125mm dia set (13 filters) FNG0300 50 x 50mm set (12 filters) For storage boxes (see accessories)