It's great that you call up light manufacturers for PAR wattage and have 1000w grows. (btw...having two separate lights is often better because the intersection points of the two lights have an area that is receiving good light from two directions. It's like a Venn diagram.) But most people aren't doing grows that big. Lots of people live in foreign countries where they can't just call light manufacturers. And, again, you don't get any particular benefit from PAR watt information IMO. The people that are pimping PAR watts are grow light manufacturers. There are plenty of threads that discuss whether PAR is useful, but I'm just not seeing a whole lot of positive response from actual growers.

I'm glad you did better in a grow with a change in bulbs...but, honestly, what you're describing is a 10% difference in yield. And, as someone who has obviously done a lot of grows, you know that a ton of things can affect things that much...from having lights one inch closer, to having the dual light overlap I mentioned above, to a small change in water salts, to having a bulb that's been used twice before and has lost ten percent of its output.

For most people doing small to medium grows--let's just say under 1.75 sq meters or 20 square feet--you can make life a lot easier by using proper reflectors, keeping walls and surfaces close to your plants properly reflective, getting good ventilation. This is especially true with the small grows (under 6 sq. ft.) that a lot of people do here. My goal with this thread was to talk to them. Using lumens to compute lights needed is both easy and practical for them. Necessary light, ways to use all the light you have, not overlighting if you don't need to to avoid extra heat and stress...that's the type of practical information that I think people want. And I wish you luck with all grows, growbe.