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Neutral Density Glass Filter

The Neutral Density Glass Filters by Hellma Analytics contain a filter material by the company Schott AG. These materials were chosen due to their homogeneity and their stability. They provide a relatively constant transmission over the visible wavelength spectrum from 405 nm to 800nm. Furthermore, they have been used for decades to test the photometric accuracy and linearity in the visible wavelength range (above 405 nm).

Please note:

If you have several neutral density glass filters with different nominal absorptions, you can test the linearity of your absorption scale by entering the measured absorption values for each wavelength in a diagram against the measured values on the DAkkS calibration certificate.

Absorbance table of F390 - F303

Filter type (Art.-No.)Average absorptions at wavelength
F390 (666F390-25)0,03790,03760,03700,03670,0366
F2 (666F2-39)0,26680,24160,25250,29150,2944
F3 (666F3-38)0,54570,49700,50500,56040,5513
F4 (666F4-37)1,09351,00581,00251,06451,0225
F201 (666F201-39)0,31610,28640,30160,35020,3554
F202 (666F202-36)1,66361,53501,50661,54241,4525
F203 (666F203-36)2,17212,01052,00232,04781,9275
F204 (666F204-37)0,75510,70120,70360,71870,7229
F301 (666F301-361)2,66782,48562,50892,54432,3797
F303 (666F303-361)3,18762,96922,99563,03782,9046

Neutralglasfilter Typical spectrum of the neutral density glass filter, taken with a slit width of 1 nm

Article-no.666F0-71, 666F2-39, 666F3-38, 666F4-37, 666F201-39, 666F202-36, 666F203-36, 666F204-37, 666F301-361, 666F303-361, 666F390-25
ApplicationTo check the photometric accuracy in the Vis range (405 nm until 890 nm)
ContentF0: Empty frame (without glass)
F2: Neutral Density Glass NG11 (0,25 Abs)
F3: Neutral Density Glass NG5 (0,5 Abs)
F4: Neutral Density Glass NG4 (1,0 Abs)
F201: Neutral Density Glass NG11 (0,3 Abs)
F202: Neutral Density Glass NG3 (1,5 Abs)
F203: Neutral Density Glass NG3 (2,0 Abs)
F204: Neutral Density Glass NG4 (0,75 Abs)
F301: Neutral Density Glass NG9 (2,5 Abs)
F303: Neutral Density Glass NG9 (3,0 Abs
F390: Neutral Density Glass BK7 (0,04 Abs)
Standard certificationWavelength: 440; 465; 546.1; 590; 635 nm
Slit width: 1 nm
with DAkkS calibration certificate
Possible certificationsAll wavelength from 405 nm to 890 nm possible
Over 890 nm also possible with Hellma Analytics calibration certificate.
Slit width: all until 5nm possible

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