Uhm….no. Sorry I meant 75 instead of 71mm. Typo………

The UF-1508 was available with either:
38, 50, 67 or 75mm head. These measurements relate to the outer diameter of the head, not to the diameter of the lens.
For instance: the 75mm head has a 69mm lens in it.

This in turn translates to 3.739 mm2 lens surface. Combine that max. luminance per mm2 of the led and you have the theoretical max throw (allow for 95% lens transmittance).

Cheers,
Nico