Hellma Analytics neutral density glass filters are made from filter materials produced by Schott AG, which were selected on account of their homogeneity and stability. Thanks to a relatively constant transmittance within the wavelength range of 405 nm to 800 nm, they have been used to check photometric accuracy and linearity in the visible wavelength range (> 405 nm) for decades.
Please note, the thickness of the filter is set at the manufacturing so that the specified nominal optical density (values from 0.04 to 3.0 Abs) obtained at 546.1 nm. This results in slightly increasing absorptions at shorter wavelengths.
Typical spectrum for Neutral density glass filters F390 - F303 im Bereich von 405 - 800 nm, measured with a slit width of 1 nm.
|Type||Art.-No.||440 nm||465 nm||546.1 nm||590 nm||635 nm|
|F390||666F390-25||F390: Optical Glass BK7 (0.04 Abs)|
|F2||666F2-39||Neutral Density Glass NG11 (0.25 Abs)|
|F201||666F201-39||Neutral Density Glass NG11 (0.3 Abs)|
|F3||666F3-38||Neutral Density Glass NG5 (0.5 Abs)|
|F204||666F204-37||Neutral Density Glass NG4 (0.7 Abs)|
|F4||666F4-37||Neutral Density Glass NG4 (1.0 Abs)|
|F202||666F202-36||Neutral Density Glass NG3 (1.5 Abs)|
|F203||666F203-36||Neutral Density Glass NG3 (2.0 Abs)|
|F301||666F301-361||Neutral Density Glass NG9 (2.5 Abs)|
|F303||666F303-361||Neutral Density Glass NG9 (3.0 Abs)|
|F0||666F0-71||empty frame (without glass), reference filter|
|Standard Measurement||F390 - F303 Wavelengths: 440, 465, 546.1, 590, 635 nm |
Slit width: 1 nm; with DAkkS calibration certificate
|Possible Measurements||all wavelengths from 405 to 890 nm possible. - Over 890 nm is also possible with Hellma Analytics calibration certificate. |
Slit widths: all up to 5 nm
If you have several Neutral density glass filters with different nominal absorbances, you can check the linearity of your absorbance scale by plotting the absorbance values measured for each wavelength against the measurement values on the calibration certificate in a diagram.