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I was just going to tag you lolIf you are without a light meter at all, keep in mind that there's no reason to spend a big pile of money for basic measurement capabilities.
Start off with a $free [HASHTAG]#lux[/HASHTAG] [HASHTAG]#meter[/HASHTAG] app for your smartphone. Plenty of folks here have done that already, so there are probably measurements you can compare with.
$15 (delivered) will get you a much better (and safer to use around saltwater) LX-1010B handheld meter from eBay/Amazon/etc.
Surface measurements with either of these will do at least 90% of what you're likely to need - gauging intensity and comparing measurements between old and new lights, etc. (If you have a specific use-case, let us know though!)
If you follow those tags or do a search for "lux meter" you can find plenty of thread from the past year or two...
(To pre-empt naysayers, I and others have been using these meters successfully - they do work.
There is no day-to-day conversion....no need....you just work in lux.
Conversions are for communicating with people who are (so far) only familiar with PAR or for comparing with historical PAR measurements.
If you had a serious reason to do the conversion, you'd rent that PAR meter and take parallel measurements of PAR and lux on the same light fixture. That's a REAL conversion factor that will be accurate and repeatable.
But again, generally I/we don't have any reason to convert just to use the lux meter for its intended purposes. Measure in lux....stay in lux.
There is no day-to-day conversion....no need....you just work in lux.
Conversions are for communicating with people who are (so far) only familiar with PAR or for comparing with historical PAR measurements.
If you had a serious reason to do the conversion, you'd rent that PAR meter and take parallel measurements of PAR and lux on the same light fixture. That's a REAL conversion factor that will be accurate and repeatable.
But again, generally I/we don't have any reason to convert just to use the lux meter for its intended purposes. Measure in lux....stay in lux.
There are some important numbers to know:
Those are all equally important and note there's nothing about PAR or lux involved. The answers can be expressed in either units.
- What is the intensity of direct sunlight at the equator where many corals are from?
- What is the light compensation point of corals?
- What intensity levels have people had documented success with?
The answers, roughly speaking...
- 100,000 lux or 2,000 PAR (or a conversion factor of 50)
- 5,000 to 10,000 lux
- From around 10,000 up to nearly direct sunlight levels. Many corals seem visibly stressed above ~80,000 lux. Clams are more geared for surface light levels....corals seem to be more optimized for the middle depths. From around 20,000 lux to around 50,000 lux seems to be a sweet spot for most corals.
Well...it's more like I'm fed up with speaking in terms of "yeah, it's pretty bright...38%. Yours is 58%???".
That's half a step from gibberish, but it's what most of us are stuck doing when we dial in new lights in absence of a light meter.
I (like many people past and present) have toasted a tank full of corals speaking like that.
So don't get me wrong, there's nothing wrong with using a PAR meter. You'll never hear me say that.
What you will find is that when you have a lux meter, there is no need to convert to PAR. For our purpose (which is not a sophisticated one) there is nothing inherently better about PAR units.
So it's not about avoiding PAR meters....their cost yields that effect naturally.
It's about using a meter because any meter is 1000x better that an eyeball. The fact that there are $free and $15 options that are totally legit, yet so rarely get used, is a travesty IMO.
