I would like to say what a great write up you did on how to build a par meter. I have a 250 gallon salt water tank with live coral and have been trying for awhile to find out exactly what the light out put from my bulbs is. and compare I run three 250 watt 14000K double ended Phoenix metal halogen bulbs for lighting. I have read your article and obtained the VTB8441BH diode that you talked about. I have also got the Cinegel samples that you mentioned. Towards the end of your post it appears that you choose only to use the 4815 Rosco filter. Is this correct? I am going to attempt to build one of your devices following the directions you supplied. Also do you know what number diffusers you used is this a trial and error thing? (As per the question below if required could I purchase a Par meter from you and if so how much would it cost? I also live in Canada.