What is PAR?

[mraafat]

I am new to this, so what does the PAR value mean on MH Bulbs? I currently have 13k AB, but was looking for something with more blue. I was looking at Hamilton 14k but someone told me the PAR isn't high, so I would like to know what that is. Thanks for your help!

 

[elephen]

Photosynthetically available radiation (PAR; 400ââ"šÂ¬Ã¢â‚¬Å“700 nm, E mââ"šÂ¬Ã¢â‚¬Å“2 dââ"šÂ¬Ã¢â‚¬Å“1) is the fraction of the total solar energy (Mjoules mââ"šÂ¬Ã¢â‚¬Å“2 dââ"šÂ¬Ã¢â‚¬Å“1) that is used by organisms for photosynthesis and vision.