Not to split hairs, but the PAR rating of a bulb is what's important. Lumens are a unit of measurement (to determine the relative brightness from a source of light) relating to the human eye.
Whatever your reason for growing, there is no need to be wasteful. I really hope some noob doesn't read this and thinks it's a good idea to change their lights 50 times a year.
You say your not trying to split hairs ! Are you serious , who cares if its lumens or par used to describe the fact that 99% of all 600 watt hps bulbs are the same brightness,lumens,par , brightness ect , its all the same no matter how you word it , a 600 hps is a 600 hps when it comes to light output ,period .
Your 3 posts have made it perfectly clear that YOU HAVE A PROBLEM with my " wastefull " spending as well as enviromental issues about saving space at the landfill , ive read every post in this thread & nowhere do i see you offer the OP any advice related to his questions about how to increase his yields.
Then you nit pick my advice over trivial issues that will in no way ever apply to the OP's questions or help him in any way with his yield ,next you go as far as saying you hope a newb dont read my post & replace his bulbs 50 times a year , pretty dramatic dont ya think .
Since you felt the need to correct me on using precision terminology in describing light values i'll respond with this fact , every hour ANY BRAND high intensity bulb is used the bulb's light output decreases & gives off less light , that isnt just my opinion but a well known fact , most renowned grow guru's recommend installing new bulbs every 2 grows due to this measurable light loss & the effect of the lost light output on overall yields .
Just because we cant see a change in light output dont mean the bulb is still operating at peak output , dollars lost in wasted electricity powering an inefficient bulb could easily pay for the bulbs replacement costs after 2 grows on wasted electricity alone , thats not even counting lost/added bud weights .
It seems your reasons for posting are more about your enviromental issues & personal spending than helping the OP's questions about increasing his yields , pretty sad .