Effect of Tip Diameter on the Irradiance from Curing Lights

This video uses the Bluephase Meter II to show the effect of the light tip diameter on the irradiance value. Using the power value (mW) overcomes this problem as you do not have to enter a tip diameter.
The reason why tip diameter has such an effect is because the irradiance is the power divided by the area. Even small changes in the diameter have a large effect on the area (πr²).