The light output is measured just in this center area.

They also require a warm-up period of 4 - 7 minutes to reach full light output.

It gives a more uniform presentation of the light output in operation.

These units can deliver a similar light output with reduced power consumption.

A 10 watt fluorescent would give the same light output.

That makes the glass appear darker and reduces the light output.

They are not very energy efficient, and the light output tends to decrease over time.

The light output is quite low, however, and very sensitive to variations in temperature.

This model has no low mode for light output.

The light output varied from 156,000 to 248,000 candlepower over many years.