Originally Posted by JP Owens
A 42 watt led is about equivalent to a 150 watt incandescent bulb.
That would be little more than 300% efficiency gain - less than I'd expect between FL and incandescent. LED usually is at least twice that efficient. You might be however right where dedicated photographic or video lights are concerned, as these are rather inefficient LED applications, constrained by CRI requirements and a flicker-free DC source.
From a long time of location work I can tell you that there is no reasonably meaningful relation between Watt and Lux (or Lux and Lumen) when you compare between different lamp types and technologies. The power consumption of a given location's illumination (which usually is the only thing your clients will be aware of) is no useful information when it comes to figuring out what extra illumination to bring - you cannot avoid that extra trip to inspect the site situation.