Worksheet on Radiometric vs Photometric Units

This worksheet was developed to help you better understand the difference between photometric and radiometric units.

I find very often that when people try to convert between photometric units and radiometric units, they are confused because the 'm2' and 'sr' are not where they expect them to be. Did you know that when you re-write the photometric unit you're trying to convert with only 'lm', 'm2 and 'sr', the convertion is straight-forward. This might seem a little odd, since the SI base unit of photometry is 'cd', not 'lm'. This is the reason why I developed this worksheet.

It is based on Figure 7: Measuring light – Luminous measures and their units in SynthLight Chapter 1: Fundamentals. If you haven't yet perused Section 1.2 Photometry of this document, now would be a good time before you get your fingers dirty on the worksheet.

Here is a local copy of Synthlight Chapter 1: Fundamentals, just in case the Internet breaks as you are reading this.


Click here or on the image above to download the worksheet (PDF, 50kB)