The IR heating function serves to assist in heating the camera during cold circumstances, by taking advantage of the IR LEDs' heat dissipating property while turned on. Since the IR LEDs are located very close to the camera lens, this function is especially useful to keep the front glass clear.
This feature was introduced in the PD910 and PD920 cameras, where it’s found in the web page Camera menu, under IR function:
In the PD950, the selectable options were rephrased to better reflect the actual behavior:
PD950 IR heating mode "Colder" best matches PD910 entry "Off". It better represents the function, since the IR heater does not turn completely Off, it only turns on when it's colder.
Likewise, for "Warmer" and "On": it doesn't mean that the IR heating is always on, it rather means that the heating function turns on when it's warmer.
The extra PD910 mode "Intense" was dropped.
It is planned to have an extra PD950 IR heating mode "Disabled", which completely turns off the IR heating function.