White Paper: Standard Pro with a Neutral Density Attachment to replace High Lux Lighting Passport
By: Rez Mani (Application Scientist, Allied Scientific Pro)

In this white paper, it 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 transmittance 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 R and Rvalues.

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% transmittance nominal) and is shown in figure 1

Odoo CMS - a big picture

Figure 1: FROD60 from Newport

In order to make consistent measurements and eliminate variation due to spatial variability, a filter holder was designed that would clip on the Standard Pro spectrometer and holds the ND filter on top of the diffuser. This filter holder with the filter in place is shown in figure 2

Odoo CMS - a big picture

Figure 2: Filter holder to hold the ND filter in front of the standard Pro diffuser plate

The next step was to measure transmittances of the filter at high intensities for lamps of different colour temperatures. This has been done with the Spectrum Genius Transmission (SGT) app to determine the transmittance of the filter for these light sources. For the transmittance measurement, the High Lux unit was used with and without the filter.

Two 90 watt lamps of different colour temperatures, one at 5000 K and the other at 3000 K were used to make these measurements and the following results were obtained.

The illuminance levels were adjusted by different positioning of the Hi Lux unit with respect to the light source and measurements were done at 50,000, 100,000, 150,000 and 200,000 lux. The tables and pictures s in Section 1 show the results. The High Lux unit has some data filtering issues and ripples appear on the spectrum. This does not affect the transmittance measurement since both the filtered and unfiltered units have these ripples. However, it does affect the photometric measurements which will be discussed later.

Section 1: Transmittance measurements of the neutral density filter

1. 90 watt, 5000 K lamp

Odoo CMS - a big picture


1.1  Measurement at 50,000 lux

Odoo - Sample 1 for three columns
Odoo - Sample 2 for three columns
Odoo - Sample 3 for three columns
Odoo - Sample 3 for three columns

1.2  Measurement at 100,000 lux

Odoo - Sample 1 for three columns
Odoo - Sample 2 for three columns
Odoo - Sample 3 for three columns
Odoo - Sample 3 for three columns

1.3  Measurement at 150,000 lux

Odoo - Sample 1 for three columns
Odoo - Sample 2 for three columns
Odoo - Sample 3 for three columns
Odoo - Sample 3 for three columns

1.4  Measurement at 200,000 lux

Odoo - Sample 1 for three columns
Odoo - Sample 2 for three columns
Odoo - Sample 3 for three columns
Odoo - Sample 3 for three columns


Average of 4 measurements for 5000 K lamp was 24%.

Odoo CMS - a big picture



2. 90 watt, 3000 K lamp

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