Neutral Density Filter

ND-Filter

This ND-Filter is proposed to replace the Lighting Passport High Lux model which is capable of measuring illuminances up to 200,000 lux with a Standard Pro model and a neutral density filter coupled to the aperture.

The High Lux model has been discontinued and the Standard Pro model is only capable of measuring up to 50,000 lux.
Customers who would like to measure the illuminances of their high intensity fixtures and with the discontinuation of the High Lux model, have no means to do it.
The idea is to use an OD 0.6 neutral density filter that works in the visible range and has a transmission of nearly 20% to be placed on the diffuser of the Standard Pro to measure high intensity light fixtures. What needs to be calculated is the exact multiplication factor to be used once the Standard Pro measures the illuminance with the neutral density filter to give the actual illuminance. In addition, it has to be investigated if the presence of the ND filter alters the other photometric and colorimetric parameters such as colour temperature, CRI index and TM30’s Rf and Rg values. To accomplish this, the neutral density filter FROD60 from Newport was used. This ND filter is of the absorptive type and has the following specs. 12.7 mm diameter, OD=0.6 at 546.1 nm (20% transmission nominal) and is shown in figure 1.