Join Date: Jan 2008
Location: Bangalore, India
Once you use any source of light, the brightness reduces by about 15-20% in the first few weeks. Then for the next few months the amount of light gradually reduces. You have a continuously varying Par value for the lights that are used. This is true for MH, PLL, T5/T8, CFL blubs. I'm not so sure about LED's. This may be one of the reasons no one specifies the values.