The equivalent photometric quantity is known as total luminous flux, and is measured in lumens. Both of these quantities measure the total output spectral power from a light source, but the photometric value is more useful to lighting engineers as it represents what the human eye actually sees. The Photonics Cluster laboratories use a 1 metre diameter integrating sphere to measure this quantity and can measure any source up to 200 mm in diameter. The light is collected by a Bentham spectroradiometer that can measure across the entire visible spectrum. For smaller sources, the Labsphere 25 cm integrating sphere and spectroradiometer are used.

There are three other quantities commonly used in photometry:

• Illuminance (lumens per square metre)
• Luminous intensity (lumens per solid angle, also known as candela)
• Luminance (candela per square metre.)

The photonics Cluster laboratories can measure any of these quantities at a wide range of light levels, by using the Bentham Monochromator. Irradiance (watts per square metre) can also be measured in the UV and IR by using the Ocean Optics HR 2000 spectroradiometer. Together, these spectroradiometers allow the Cluster's labs to measure optical radiation from 190 nm to 1100 nm.

These instruments calculate the photometric values by correcting the radiometric spectrum by the photopic curve and multiplying by 683. This means than these calibrated instruments are repeatable to within 1%. However, the labs also have hand held light meters which incorporate filters that approximate the photopic response. These units are repeatable to about ±2%. This allows the customer to select the option of quick measurements, while making only a small sacrifice in accuracy. The labs use two Konica Minolta instruments, an LS 100 luminance meter and a CL 200 illuminance meter.

The CL 200 also takes colour measurements (see below for explanation of colorimetry.)