alton
Valuable Member
Since I have both meters, I check with both and the drop off between PAR and Foot candles is very close at least for MH.
Lux Meter, Par Meter, whats the difference??
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Cool, check it with something that has good blue and green in it and it would be interesting to see how they measure.
agreed.
I had understood/assumed it had more to do with the chemical make up of the photocell and its limitations rather than by design. thus the optical refinements in a par meter rather than simply expanding the spectral range of the cell.
it does than beg the question, what is a more accurate way of the intensity(only) of the visible light spectrum.
Its up to the user to observe intensity fall off over a long period and compare to the published studies. At 10% I would assume that loss in the first few months or a drop in household voltage(really happens).
coral husbandry is already a game of estimation and trial and error. Regardless of the method that is used to measure light or any parameter. You still have to gauge "what the coral likes" in placement of a coral and water parameters. Even a through Par mapping of a tank gives odd readings to the uninitiated, like 50 on the white sand bed and 50 half way up on a dark rock, the course of action is determined by the experience of the user in the big scheme of things ,as the available par from the light did not change. The rock just does not reflect. so personal responsibility and use of the available knowledge is always up the the user.
Lux is somewhat inaccurate,yes, so is an api test. But to rule them out as a first step for users or as a teaching tool of par is unfair, to the science and to the user.
On of the largest boons to the use of a lux meter to advanced users such as ourselves is, on a forum, if a new aquarist has difficulty he or she can report the light parameter. At 30k lux and we estimate the constant based on the fixture, 60-67, we know the light is likely ok. Or at 20,k lux on a higher end lamp @ a constant of 72, its likely ok too. But in the end he might just have one coral that wants a higher par.
leds make this much more difficult, as from manufacturer to manufacturer the constant will vary wildly. A good fixture should according to AA is around 67. Id bet money this is NOT true of many fixtures(looking at you JBJ intermediate.)
he is. Its a MH.
I was not trying to tell people to rule out Lux. I just want people to understand what they are using so they can make the proper decision about how best to use it or not use it in their tanks. I this were ten years ago, I would not be as hesitant to use lux, but now with LEDs the current trend is to have a tank that is extremely blue. The wavelengths that are being used in LED are not well represented in lux measurements. It could be easy for someone to crank up the blue LED only to find that it is not measuring much on their lux meter, then later find that they have burn up some of their corals with too much light, even though the lux meter was telling them that there was not too much light.
cool thanks. absolutely agreed. Totally same page.
One reason Par meters dont do well on LED isnt spectrum I believe. my theory:) in a multi chip array, each focused led is sending tiny beams(disco) down not a broad wash (mh t5). The Par meter dome receptor a small disk rather then a large flat disk used for indecent intensity readings . so its only picking up the individual led not the overall "incedent" reading. a wider disk would help getting more accurate readings. The Apogee 500 I believe has a wider disk now.
same reason a phone lux App doesn't work as well as the hand held, but does if you put a piece of printer paper over it.:eek:
so it likely works great on a Kessel, but not as well on as maxspect.
Is one reason Id rater pick up a less expensive Hydrofarm and play with it on led rater than the higher quality apogee. and do a comparison of those.
Great..., can you chime in on the 67 factor used to covert lux to par for blue/white LED?
http://www.advancedaquarist.com/2013/2/equipment
which meter?
I have 2 150 MH, one is twice a bright because of the reflector.
meters are fun:)
yes please.
And Imo its a good safe number to use. (been thinking about this) . Better safe than sorry.
you can also run the number from 60 to 70 and get a feel for the difference.
http://www.apogeeinstruments.com/conversion-ppf-to-lux/
Seneye -- it was given to me by someone. I am aware some people say its not very accurate but based on my tests I would say its pretty close. It gets the kelvin ratings pretty close and when I have tested floodlights with LUX/Lumen output on the box its pretty close to matching. Color temp is fairly close too although I should note the radions dont get a temp because of all the different color bulbs.
sweet thanks Ill take a look at those..
check this out from above. The paer wont cut too much or change the color too dramatically.
One reason Par meters dont do well on LED isnt spectrum I believe. my theory:) in a multi chip array, each focused led is sending tiny beams(disco) down not a broad wash (mh t5). The Par meter dome receptor a small disk rather then a large flat disk used for indecent intensity readings . so its only picking up the individual led not the overall "incedent" reading. a wider disk would help getting more accurate readings. The Apogee 500 I believe has a wider disk now.
same reason a phone lux App doesn't work as well as the hand held, but does if you put a piece of printer paper over it.:eek:
DMan
Active Member
Using a lux meter to determine when your bulbs need changing may not be that efficient. As bulbs age its not the intensity that you have to worry about its the spectrum. That will change long before the intensity changes. I've seen a few odd explanations. So here's mine (others can decide if it is just as odd). Lux is used for the human eye. It is how bright we perceive the light. It could have nothing to do with Par. Generally you don't want anything lower than 3000lux. Par is has nothing to do with the quality of light as I saw described earlier. It is more quantity of light that plants and corals need. The quality of light is referred to as PUR. Which basically means how much of a given light source is actually usable.
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