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hahnmeister · 11/17/2007, 12:19 AM

"why don't you go read Dana Riddle to whom you refereed me to"

Because it wont tell me anything needed for this 'argument'. Dont get me wrong, Im not saying I know it all, just that I know what things are wrong with what you posted. You told someone that UV exists at both ends of the visible spectrum... just beyond 700nm/red and right before 400nm/purple. Uh... the 700+ range was Infra Red last I looked. If you cant pass the 9th grade, theres no use talking about the SAT's... know what I mean?

You posted:
"Just how much data do I have to provide for you to listen. Maybe a Physics Professor from the University of Arkansas can explain to you:"

Its not a matter of how much. You can post as much as you want, but if its not correct, it doesnt make a difference.

That professor is not correct, at least not in our context. It seems in that case, he is talking about a fixed spectrum (as in, for land plants), so a relative conversion is possible. This is the only circumstance that you can compare PAR to Lumens, and only in a relative aspect at best. Its like asking how much diesel you can use to replace unleaded gas in an engine and get the same power... it just cant be done. Sure, there are relative comparisons for horsepower and torque based on the engines you use these fuels in, but you cant compare them directly.

PAR takes the raw photon count per an area... raw visible radiant energy (radiometric scale). It wouldnt make a difference which planet you are on, or what species you are (how you percieve the light), the PAR would be constant. The photometric scale is scaled to what our eyes see. Its the total photon count, but the blue is only counted at 10%, the green at 100%, and the red at 85% (I know those numbers are not exact, but off the top of my head, thats pretty much what its like). Its because our eyes dont see blue light (only 10% of our cones are tuned to see blue in daylight conditions), so having a very blue light might make it seem very dull to us (or in the photometric scale), yet to a coral, which is more than likely primarily depending on blue light in the first place... it could be very bright.

It may seem extreme, but to convert PAR to lumens is something like asking this: "how much red light does it take to equal a given amount of blue light?"... as if there was some way to keep adding red light until you get blue or something. It just doesnt work like that.

So a 10,000K bulb that looks very bright to us may have a PAR of 400 w/o a reflector at 12", and the matching lux rating might be 800 (unitless ratio number). But lets say you have a 20,000K bulb with a PAR of 400 at 12" w/o reflector... one with a huge 460nm blue spike. Well, a lux meter isnt going to pick this up so well, so it might register at 400 only, even though the PAR is the same. To the coral, what we cant see as well (blue) means very little. In fact, bluer light (shorter wavelength, higher frequency) contains more energy (and needs more energy to produce) than longer wave light (red uses less than green, green uses less than blue). And UV is even harder to make (contains more energy). If you read Dana's articles, you will see how he talks about UV photoinhibition alot... he covers it pretty well. But in the same respect, you could have a coral under 200 micromol/m2/s of light with a daylight spectrum and it could do just fine, but if you switch to a primarily blue bulb of that same 200 micromol/m2/s you could end up photoinhibiting (burning) the coral. This is also why bluer halide bulbs tend to have lower PAR than daylight bulbs... bluer light takes more energy to produce.

So its not that manufacturers are manipulating PAR readings by boosting the blue spectrum. Most mfg's give lumen ratings anyways for their bulbs, so trying to manipulate these readings by creating artificially high blue spikes wouldnt do them much good, as the photometric scale doesnt pick it up as well.

If you want, I can go around to all your posts, quote every piece of untrue info, and we can deal with it one on one to get you on the right track.

11/17/2007, 12:19 AM	#58
hahnmeister Moved On Join Date: Sep 2005 Location: Brew City, WI Posts: 10,156	"why don't you go read Dana Riddle to whom you refereed me to" Because it wont tell me anything needed for this 'argument'. Dont get me wrong, Im not saying I know it all, just that I know what things are wrong with what you posted. You told someone that UV exists at both ends of the visible spectrum... just beyond 700nm/red and right before 400nm/purple. Uh... the 700+ range was Infra Red last I looked. If you cant pass the 9th grade, theres no use talking about the SAT's... know what I mean? You posted: "Just how much data do I have to provide for you to listen. Maybe a Physics Professor from the University of Arkansas can explain to you:" Its not a matter of how much. You can post as much as you want, but if its not correct, it doesnt make a difference. That professor is not correct, at least not in our context. It seems in that case, he is talking about a fixed spectrum (as in, for land plants), so a relative conversion is possible. This is the only circumstance that you can compare PAR to Lumens, and only in a relative aspect at best. Its like asking how much diesel you can use to replace unleaded gas in an engine and get the same power... it just cant be done. Sure, there are relative comparisons for horsepower and torque based on the engines you use these fuels in, but you cant compare them directly. PAR takes the raw photon count per an area... raw visible radiant energy (radiometric scale). It wouldnt make a difference which planet you are on, or what species you are (how you percieve the light), the PAR would be constant. The photometric scale is scaled to what our eyes see. Its the total photon count, but the blue is only counted at 10%, the green at 100%, and the red at 85% (I know those numbers are not exact, but off the top of my head, thats pretty much what its like). Its because our eyes dont see blue light (only 10% of our cones are tuned to see blue in daylight conditions), so having a very blue light might make it seem very dull to us (or in the photometric scale), yet to a coral, which is more than likely primarily depending on blue light in the first place... it could be very bright. It may seem extreme, but to convert PAR to lumens is something like asking this: "how much red light does it take to equal a given amount of blue light?"... as if there was some way to keep adding red light until you get blue or something. It just doesnt work like that. So a 10,000K bulb that looks very bright to us may have a PAR of 400 w/o a reflector at 12", and the matching lux rating might be 800 (unitless ratio number). But lets say you have a 20,000K bulb with a PAR of 400 at 12" w/o reflector... one with a huge 460nm blue spike. Well, a lux meter isnt going to pick this up so well, so it might register at 400 only, even though the PAR is the same. To the coral, what we cant see as well (blue) means very little. In fact, bluer light (shorter wavelength, higher frequency) contains more energy (and needs more energy to produce) than longer wave light (red uses less than green, green uses less than blue). And UV is even harder to make (contains more energy). If you read Dana's articles, you will see how he talks about UV photoinhibition alot... he covers it pretty well. But in the same respect, you could have a coral under 200 micromol/m2/s of light with a daylight spectrum and it could do just fine, but if you switch to a primarily blue bulb of that same 200 micromol/m2/s you could end up photoinhibiting (burning) the coral. This is also why bluer halide bulbs tend to have lower PAR than daylight bulbs... bluer light takes more energy to produce. So its not that manufacturers are manipulating PAR readings by boosting the blue spectrum. Most mfg's give lumen ratings anyways for their bulbs, so trying to manipulate these readings by creating artificially high blue spikes wouldnt do them much good, as the photometric scale doesnt pick it up as well. If you want, I can go around to all your posts, quote every piece of untrue info, and we can deal with it one on one to get you on the right track.