Intensity and depth penetration of pc lighting.

[saltyrich]

I'm aware of the different intensities between popular reef lighting (vho, pc, mh). Many have commented on this board about effective depth of pentration of vho and mh lighting. I'm curious about the intensity and penetration of pc lighting. Can someone offer up some words of wisdom?

 

[melbournefl]

Good Morning Salty,
Since I'm not a lighting engineer I'm going to quote from John H. Tullock's book, Natural Reef Aquariums here ...
***
In order for the light to reach from the surface to the bottom of the tank, we must take into account a principle of phisics called the Inverse Square Law. This states: "the intensity of light falling upon an object decreases in proportion to the square of the distance between the object and the light source." For our purposes, this can be translated, "If you double the distance between the lamps and a photosynthetic organism growing in the tank, you'll need four times as many lamps in order for the organism to continue to grow at the stam rate."
***
Hope this helps you more than me, all it told me was, no matter how many lights I cram in this big ol' hood, it ain't gonna be enough LOL
Later,
Paul

 

[jonthefb]

mel, thats pretty much my conclusiion as well, and to think all i have is a 20!!!! that reference makes sense though if you think about it!
good luck
jon

 

[melbournefl]

*sigh* I know it makes sense Jon, that's the sad part! I'm building a 250 gallon tank right now and the lighting costs haven't even started yet (my probably-soon-to-be-ex-wife, is going to kill me when she finds out those costs!) I've already concluded that the most practical approach to my next tank will be to:
1) pave over the entire back yard
2) build the tank outdoors, thereby avoiding all lighting expense
3) make tank only 6 inches high but REAL WIDE & LONG
Should make the whole thing much more reasonable!
Later,
Paul

 

[saltyrich]

I'm really only concerned with the intensity of pc lighting at the top of the tank. For example, how intense in comparison to other types of lighting etc. is pc that is approximately 6-8 inches above possible corals?

 

[slowest is fastest]

For an example of how much light penetration is realized from two 55watt PC bulbs go here (and a lot more info)
http://www.aquabotanic.com/lightcompare.htm
But to answer(?) your question the example calculation used in the above article yielded PAR illumination as 123 uE/s/m2 of light at 16" from two 55watt PC bulbs(the effective intensity and penetration of PC measured in PAR)
If you want a better understanding you should really read the entire article (as well as others) Without a working knowledge of all factors that have to be considered the lighting issue only becomes more confusing. With a little time and patients you will quickly understand why it is much easier to understand the "whats" and "whys" while at the same time find it difficult to articulate them in laymans terms in a short post (or at least I do).
In short I believe anyone is capable of understanding lighting issues but it takes a gift few have, to explain and corroborate with some integrity the specifics, as there are far to many subtle variables to get a "black and white" answer. IMHO
Regards,
SiF

 

[jonthefb]

man i am gonna have to borrow the light intensity meter from the bio dept here at the university. we always use this thing on our research trips and it measures the same in micro einsteins per second per meter squares. im gonna have to borrow it and check out what the reading is over my tank!
good luck
jon