PAR value lighting questions.

[wattsupdoc]

I'm a little confused on the par values of MH and T5HO's. I mean, I totally understand each lighting method, but in PAR comparisons is where I need a little guidance. In sanjays reef lighting page, it gives some specs for each lamp, lit by ballast. My question here is, is the PPFD the par value for that lamp/ballast combination? Or is it representing something else that can reflect the PAR value in some way. I understand that the higher that number the better the PAR, but is that the exact Par value? Granted I understand that there may be variances from bulb to bulb, ballast to ballast, day to day.

Also, I believe I saw a thread or some reference to different lamp PAR values for T5HO's somewhere. Heck, I know I did I've seen them several times, but for the life of me cant find them now. Can someone please point me in the right direction?

TIA,
Charlie

 

[juststartingout]

Hi Charlie,

"My question here is, is the PPFD the par value for that lamp/ballast combination?"

I don't belive so, when recently discussing a lamp ballast combo, someone stated they were getting sometning like 900 PAR, when the same combo on Sanjay's site stated it was 182 PPFD. The combo was a 10K 250wt SE XM bulb driven by a PFO 250wt HQI ballast. With that being said, they must be different?

 

[GSMguy]

on sanjays site each value represents a bulb ballast and reflector combination.

 

[juststartingout]

Charlie,

Try this link...
http://www.reefcentral.com/forums/showthread.php?s=&threadid=918935

 

[kgross]

Sanjay's site does give the actual par value he measured, but this can not be used to compare with other par measurements. Sanjay standardized his tests with no reflector at a set distance so that the numbers he has are valid to compare the different bulb/ballast combinations. If you change the distance to the meter your par level will go up, If you add a reflector your par will go up. If you add a better reflector your par will go up even more.

So use Sanjays site to compare bulb/ballast combos to get the par/color that you want. Then add a good reflector your setup, and you will get more par that Sanjay did.

Lighting is very confusing and with different people publishing par data, it is even more confusing, since if they do not use the exact same setup, you can not compare the par levels directly. I know with JBNY's 250 watt setups, he also standardized his testing, but to compare with Sanjays, there is a conversion factor, since they measured at a different distance, if I remember correctly.

Kim

 

[wattsupdoc]

Thanks for the link!!

I understand that there are different bulb/ballasts combinations.....I think that thats pretty clear that it is.

So, then PPFD IS the same thing as PAR? I didnt realize these were without a reflector of any kind. It would be very beneficial,to know the distance from the bulb that he measured at. Anybody? I understand that comparing Sanjays info, to Grim reefers T5HO info shouldnt be done. But if you look at the par of say my 250 XM 10,000k, on an ice cap EB. Then look at grim data on the Ati prosun,........It definetly looks like the T's smoke the
MH.

BTW, I recently converted from T5HO's to MH. I definetly like the look of the MH better. I would just like to see a side by side comparison of the two systems. All things else being equal, or as close as the could be.
Anyhow, thanks a lot all.

 

[kgross]

To be able to compare anything, you would need to know the distance from the bulb, which I think Sanjay has on his set, and the distance that GR used as well as if GR was using a reflector.

The problem with a side by side comparison is that the different types of light put out light in a different area. MH is a point source, so that any part of the tank the same distance from the core of the bulb, will have very close to the same amount of light, so when you move say right or left a MH light will decrease. With a T5 or other florescent bulb, when you move down the bulb, the light does not change, only when you move away from the axis of the bulb, rather than the point light source.

So if at the same distance from the bulb a t5 put out the same amount of light as a MH, the T5 would be putting out a lot more usuable light fo the tank, since that light would be put out over the total length of the bulb, which is much longer.

Lighting is a fun subject to put it mildly there is a lot to it, and most of it has not be studied enough to compare. A MH bulb will have a much higher par level at the same distance to a T5, but where it gets really complicated is the total amount of light that makes it into the tank,