I added 32% to the underwater par number. Then I used 50 as the lux/par conversion. I didn't add anything to the lux reading because the "immersion affect" is unknown. That 32% number only applies to the mq500, nothing else.
Par to lux conversion - real world T5 numbers
- Thread starter Scott.h
- Start date
- Tagged users None
from the white paper.
More radiation is backscattered out of a radiation sensor diffuser in water than in air because the refractive index of water (1.33) is greater than for air (1.00). This is called the immersion effect. Without correction, sensors calibrated in air provide only relative values underwater
you should add it to the lux too.
and the bouncing 7% and 32% factor model to model makes NO sense according to the white paper.
OP
OP
Scott.h
Valuable Member
That used to be the case but the MQ 500 is supposed to be able to read those wavelengths around the 400 wavelength mark properly, where previous meters lacked.
OP
OP
Scott.h
Valuable Member
its kind of mind boggling. If a measure of light is "X", would a coral not see the light just as the meter and receive "X" weather it's in the water or air?
This is from the RB article:https://reefbuilders.com/2016/08/26...ent-is-strongly-impacted-by-immersion-effect/
Chief Scientist at Apogee Mark Blonquist explained that the different measurements is an ‘Immersion Effect’ which affects their different sensors differently. Apparently, measuring light intensity underwater is a field all its own because of the interplay between diffusing material, translucence, refraction and light scattering and this passage from “Measurements of Spectral Irradiance Underwater” by Tyler & Smith:
‘When a translucent, diffusing material is submerged in water the change in index of refraction at the boundary of the diffusing material results in a larger percentage of the incident radiant flux being back scattered into the water than would be back scattered into air. This immersion effect is the result of changes in interface reflections, both internal and external, combined with multiple scattering within the diffusing material.’
The SQ200 uses a completely different lens than the MQ500 so the refraction index under water is different. Also the lens outer cover an sq200 is clear while the mq500 is frosted. No one knows what the refraction index is for an underwater milkwaukee lux meter so doing it makes matters worse.
true, but it should only change the conversion number. So its plausible that and older meter would give you a slightly par/lux number.
What I was referring to is a C+ has more par than a B+. according to those sources. a 20k has less par than 14k according to the AA and apogee at the same lux intensity.
.
Its where the convo becomes circular a bit. the coral is only goind to see light one way. its the meters that react differently in air and water.
The implication is, if you did par chart in a dry tank, you would get a 30% lower reading than after you put it in water. because of refraction in water you lose 30% on the meter.
personally I think once you know that you have X amount par at the top, you can assume is X all the way to the bottom. you can substitute lux for par, as long as your aware of the coversions.
in fact if there were no par meters youd still be fine. as you be judging on intensity alone. couple that with most corals ability to take incredibly wide ranges of par.
it used to be said you need a LOT of light. In fact new science says we dont. thus my confusion in the lux par debate, if the conversion est its off 75 to 100, a xenai will take near 0 or nrealy full blast led like in my tank.
sps and acros. 250 and 350 is now recommended. some took 150 w mh inches above the tank. thats a lot more than 350. I get 65000Lux or more at 10 in from my MH w a 20k radium bulb. use the AA calculations to figure that par out.
like the dome on a lux meter.
so your both still saying lux par doesnt work because of what apogee is saying.
even though apogee says lux par conversions work and are on the site.
same for the AA articles mentioned.
How accurate is the question your both targeting. Id say in this t5 test the est of 40 as a conversion was pretty good. Id recommend to anyone using lux and always do to do the est at 40 45 and 50 to get a ball park range. Most corals seem to be fine in that kind range if the nutrients are balanced for it.
OP
OP
Scott.h
Valuable Member
Thats true. I have corals that have broken off and are growing by the sand in the back of the tank with almost no light. And I have Xenia spreading up next to an acro and loving it. They'll definitely adapt. I feel if you have light that produces a touch over 300 you can keep anything, maybe less.true, but it should only change the conversion number. So its plausible that and older meter would give you a slightly par/lux number.
What I was referring to is a C+ has more par than a B+. according to those sources. a 20k has less par than 14k according to the AA and apogee at the same lux intensity.
.
Its where the convo becomes circular a bit. the coral is only goind to see light one way. its the meters that react differently in air and water.
The implication is, if you did par chart in a dry tank, you would get a 30% lower reading than after you put it in water. because of refraction in water you lose 30% on the meter.
personally I think once you know that you have X amount par at the top, you can assume is X all the way to the bottom. you can substitute lux for par, as long as your aware of the coversions.
in fact if there were no par meters youd still be fine. as you be judging on intensity alone. couple that with most corals ability to take incredibly wide ranges of par.
it used to be said you need a LOT of light. In fact new science says we dont. thus my confusion in the lux par debate, if the conversion est its off 75 to 100, a xenai will take near 0 or nrealy full blast led like in my tank.
sps and acros. 250 and 350 is now recommended. some took 150 w mh inches above the tank. thats a lot more than 350. I get 65000Lux or more at 10 in from my MH w a 20k radium bulb. use the AA calculations to figure that par out.
OP
OP
Scott.h
Valuable Member
The diffusion of light under water in relation to air wasn't talked about a year ago. So to me, the question arises. Were these coral farms and saltwater supply companies that said coral "X" needs a light intensity of "X" taking this into account over the last few years? I'm having to assume no, even though we already know corals can adapt, even though the measurement might technically wrong, ..maybe it's not so much. Meaning those numbers were produced with that error unknowingly.
Yes, yes they were.
I came across an article By Julian Sprung and others written some years ago. They were attempting to describe corals more in zones(like agriculture) than hard numbers. Def a better idea than the stock, high med low. Imo thats silly.
and at a point I do belive its numberchasing. Beyond affordability, Its one of the reason i do think lux is an ok and reasonable way to estimate. Your looking for a range, and not really a solid number.
And its a LOT more accurate tan saying 36%. and I think there was probably a time when there was no par meter. So if watts per gallon wasn't considered stupid, im not sure why a lux meter is esp when you consider some 150w mh give half as much light as others, and Id assume the same w t5 because of ballast and reflectors..
Thanks for doing the test Scott. Very cool. To bad you live in the land of ice and snow. I have 5 brands of led, 2 Mh, and some T5s Ill be testing soon.
OP
OP
Scott.h
Valuable Member
I wasn't sure on this, so I wanted to call and talk to the companies I get my corals from. I called two well known internet companies, (I won't mention names out in the open so I can keep them to myself 
) but both said they both have the same meter as me, and when they say hit "X" range for "X" coral those were real numbers read right off the apogee screen with the probe in the water. He's telling me the highest light sps they have, such as the strawberry shortcake like 450 but other then that 400 at the surface or on the tips is good. Again, by what the meter says. So even if it's wrong, it's right 
) but both said they both have the same meter as me, and when they say hit "X" range for "X" coral those were real numbers read right off the apogee screen with the probe in the water. He's telling me the highest light sps they have, such as the strawberry shortcake like 450 but other then that 400 at the surface or on the tips is good. Again, by what the meter says. So even if it's wrong, it's right
hahahaa..I wasn't sure on this, so I wanted to call and talk to the companies I get my corals from. I called two well known internet companies, (I won't mention names out in the open so I can keep them to myself
OP
OP
Scott.h
Valuable Member
ill give you one better. My neighbor calls last night and says hey what's up. My wife asked me to ask you if you're growing weed in the basement. Lol. So I walked outside and all the basement Windows now glow blue. I'm thinking that might be more profitable, but no. Lol
hahahaa......Those lights are pink now......Ive been told.
OP
OP
Scott.h
Valuable Member
Yeah no clue. When my bulbs came
In broke last week someone said go hit up the pot shop. Never even thought of it. I kinda figured those guys would be using LEDs now. None the less this fixture is bright!
Acro maniac
Well-Known Member
- Joined
- Aug 10, 2016
- Messages
- 851
- Reaction score
- 425
- What state or country do you live in
- Florida
Ive got an all led dyi setup and recently dabbling with lerning more about lighting.
I just scratching the surface before diving all in. I downloaded an andriod app lux meter yesterday.
Sweet spot under both fixtures is 32k lux at water surface, 26k just under surface 13k-14k @12" and 5k-6k @ 24"
Im trying to convert to par which is a division of 60.
My question is did you all ever land on a correction factor for water?
I know you went back a forth but where did you end up? 33%?
I just scratching the surface before diving all in. I downloaded an andriod app lux meter yesterday.
Sweet spot under both fixtures is 32k lux at water surface, 26k just under surface 13k-14k @12" and 5k-6k @ 24"
Im trying to convert to par which is a division of 60.
My question is did you all ever land on a correction factor for water?
I know you went back a forth but where did you end up? 33%?
OP
OP
Scott.h
Valuable Member
Youre going to be really close to 100 par at 24 inches. There very well may be an error factor, but talking to the people that grow corals for a living, if they're telling me to hit between 150 par and 250 par for coral "X", with 200 being the ideal, looking right off the screen of the same meter it doesn't really matter what the number is. If that number works the best, it is what it is. I've seen comparisons from the li-core. For a 3k dollar difference it's pretty dang close. Corals adjust anyway so start low and work up slowly.
Acro maniac
Well-Known Member
- Joined
- Aug 10, 2016
- Messages
- 851
- Reaction score
- 425
- What state or country do you live in
- Florida
I have sps high, mid and some 1" from the bottom and all are well. I just wanted to understand a little better about whats going in my box.
If there was some tweeking i could do i would consider it.
