lighting theory - very long post!

AshK said:
LOL i read over your theory too quickly. As soon as I saw "Rex Grigg" I got thrown into a rage. I really absolutely despise that web page. So many people consider it the coolest thing since sliced bread.....and it doesnt even work. Sorry for my behavior.
Click to expand...

No problem. Fuzzy math makes me mad, too.

AshK said:
But yes, now that I actually read your entire post I give you 2 thumbs up:thm::thm:. Now to work on something involving PAR LOL.
Click to expand...

Thanks! PAR is indeed the next goal. My gut says there has to be some way to take a bulb's stated lumens/watt and *K and come up with something useful... not PAR per se, but a translation of lumens/watt into something that isn't centered on what the human eye perceives. Haven't worked it out yet...

...and seeing as I have to be bright-eyed and bushy-tailed at work in the morning, I should really put this aside for now and go to bed. But you haven't seen the last of me. I'm like a dog with a bone when it comes to stuff like this!
 
Yeah, I myself have issues with Rex, He may be a cool guy to be around, but sometimes he does come off a bit "fruity as a fruitcake". What irritates me most about Rex is that he seems to think that his way is the only way, and his followers follow blindly without question. His lighting theory is also off, by several factors. His rant about deep tanks and lighting is one. Don't care how well you slice it, deep tanks will have PAR issues unless you throw a ton of light over it. A difference of 12" in depth IS going to lower your PAR levels at the bottom. Even MH and LED will struggle past 24" depth.

And You really can't translate Lumens to PAR, Because while lumen is heavily weighted in the green, PAR is weighted in the blues and reds (where the human eye has a hard time seeing). No matter how well you try, it just doesn't translate.

But I am glad that someone here sees the big flaw with the WPG "guideline", whereas some on this forum (and others) think there is no alternative, or have failed to grasp basic electricity principles (I.E. Watts is not light). Though I have come up with an LED guideline for a planted tank, it is again, far from perfect and really depends on how tall your tank is. And I have added a disclaimer hoping people will not take it and run with it too much when better LEDs come about.
 
Accidently stumbed in here by mistake from the SW area, but just had to chime in and agree what others have said..

PAR is the ONLY measurement you should look for when dealing with photosynthetic species, whether it be plants or corals. PAR is the only meaningful measurement for them, all other measurements like Lumens and Lux only pertain to how the human eye interprets the light they are visually seeing. To me, the WPG rule went out the window last century. ;)

To get a PAR reading you need a PAR/PPFD meter and you check multiple locations underwater to get the different PAR values. PAR varies greatly at different locations underwater. It will be the highest reading at the surface of the water directly under the bulb, and taper off as you move away.
 
cellodaisy said:
Thanks! PAR is indeed the next goal. My gut says there has to be some way to take a bulb's stated lumens/watt and *K and come up with something useful... not PAR per se, but a translation of lumens/watt into something that isn't centered on what the human eye perceives. Haven't worked it out yet...
Click to expand...

I don't think that will be possible. Take a look at the following light bulb comparisons:

http://www.aquabotanic.com/lightcompare.htm

Note two bulbs: ADV850 (Philips Advantage fluorescent, 5000K F32T8/ADV850) & TL950 (Philips TL950 5000K fluorescent very high CRI (98) F32T8/TL950)

The two bulbs have almost identical specs (32w, 5000k, T8s, same manufacturer) yet the first one is one of the most efficient in terms of PAR while the other (with the higher lumens and CRI) is one of the worst. So that rules out using lumens and k ratings as an effective proxy for PAR.
 
Once misconception about deep tanks does need addressing - the idea that certain types of light can "punch down" through the water column better than others. OK, some light frequencies are scattered more than others through the water, but there seems to be an idea that there's some kind of "punching power" quite independent of intensity. The way some people talk you'd imagine that some light hits the water and gives up, whilst other kinds of light go flying past much faster and straight through. Einstein's corpse must spin in its grave.
 
Cory Keeper said:
You really can't translate Lumens to PAR, Because while lumen is heavily weighted in the green, PAR is weighted in the blues and reds (where the human eye has a hard time seeing).
Click to expand...

Ace25 said:
PAR is the ONLY measurement you should look for when dealing with photosynthetic species, whether it be plants or corals. PAR is the only meaningful measurement for them, all other measurements like Lumens and Lux only pertain to how the human eye interprets the light they are visually seeing.
Click to expand...

phanmc said:
I don't think that will be possible. Take a look at the following light bulb comparisons: http://www.aquabotanic.com/lightcompare.htm
Click to expand...

You are all right. As I was lying awake in bed thinking about this stuff, I realized that the stated color temperature (K) of a fluorescent is a weighted average of the K emitted by each of its phosphors. That's why bulbs with the same K and lumens/watt could have different PAR---they have different mixes of phosphors. :wall:

KarlTh said:
OK, some light frequencies are scattered more than others through the water, but there seems to be an idea that there's some kind of "punching power" quite independent of intensity.
Click to expand...

Hmmm... if certain wavelengths are more scattered, wouldn't they "punch down" less? And wouldn't it then stand to reason that light emitted at a wavelength that doesn't scatter as much in water would "punch down" more? I know that blue gets more scattered, but some resources seem to indicate that red passes through and others indicate that it is absorbed by the water (and turned into heat). :help:

I really have to get some work done now. Waaaay too much loafing off at AC during the work day recently. :o
 
Yeah, there would be some difference, but I doubt it's significant over the wavelengths available to us in aquarium lighting.
 
I believe the longer wave length is scattered,absorbed more(red,yellow,orange,)
while shorter wave lengths can penetrate deeper(violet,blue,green)
much of the visible light is absorbed/scattered in the first 33' the surface turbulence also comes into play as light is also reflected off the surface.

(random scattered thoughts);)
 
You must log in or register to reply here.
AquariaCentral.com
Top Bottom