Playing with a lux meter and reflectors

[Rider509]

Curious about how much light was hitting my plants I bought a light meter. I'm running a 600W MH during the veg stage. To take measurements I held the light sensor pointed up and at plant top level. Directly below the light I was getting 60,000 lux, but the light fell off to 35,000 lux on the edges. Not bad. I raised the light by 4" and things evened out somewhat, to 55,000 and 40,000.
I then played around with some magnet mounted home-made reflectors. The light on the outside edges jumped 5000 lux with the light sensor held straight up. The biggest difference was the amount of light reflected back into the outside of the outer plants. The reflector added 10,000 lux to the peripheral plant edges.

Disclaimer: I was bored and left unattended. Your mileage may vary. Objects in side mirrors are closer than they appear.

 

[Fuzzy Duck]

Interesting experiment

Any chance off providing a grid reference of lux readings and grow box size please.

 

[Rider509]

I'll double check and document my findings and create a graphic representation over the weekend. I'm glad someone found this interesting!
Thanks Fuzzy Duck!

 

[Weaselcracker]

You don't happen to have a dimmable hps ballast do you?

 

[Rider509]

Now you have me curious!
Yes I do. What do you have in mind?


Sent from my iPhone using 420 Magazine Mobile App

 

[Weaselcracker]

I'm wondering how much efficiency is lost when a bulb is dimmed. And how efficient a larger bulb is when run off a lower wattage ballast.

Like- how a 1000w bulb dimmed to 600 compares to a 600w bulb on the same setting
or- how a 600 dimmed to 400 compares to putting a 400 in the socket on that setting.

My practice has been to put the largest size bulb in the socket- and then just dim it to whatever setting I want, as opposed to switching bulbs all the time.

For the last few years my 1000w ballast has been running at 600, with a 1000w bulb. (I only need a 600 watt light- I just happened to have the 1000w dimmable ballast because the stoners at my grow supply place sent it to me by mistake. They're always screwing up my orders, it's just what they do. )

That ballast finally died. I ordered and just received a 600 W ballast for its replacement, but it didn't arrive with the bulb I ordered because the stoners in shipping forgot to include it. So this 600w ballast is currently running the same thousand watt bulb I was using before.

So this question of switching bulbs around is something that's been on my mind pretty often over the years- but it's especially on my mind right now. I've looked online in the past and I just went and scoured the internet again this week but there's really not much technical information out there. There is one decent study which says they do lose efficiency when dimmed, and also the spectrum range is affected, though not by very much especially for a hps.

Online mostly all I get is people who don't have any clue at all what they're talking about, just reacting saying that it's 'dangerous' and the bulbs will explode or, apparently, whatever other random bit of scary 'information' comes into their minds. It's amazing how frightened people are about such things, and how eager they are to tell you what an loser and an idiot you are for not being as frightened as they are. So sweet and touching. But not very helpful when I'm just looking for the facts.

Dimming a bulb does not make it explode or cause any other dangerous reaction. Hid bulbs are widely used for industrial lighting and often dimmed in these situation- warehouses at night, etc.

I emailed the maker of my replacement ballast with a bunch of questions but haven't got a reply yet. Chances are they don't have any idea and don't even actually make the ballast- just buy it retail from some Chinese distributor and re-label it.

If your curiosity with the meter ever leads you to doing a little investigating of the light intensity levels in these different situations, I'd be super grateful and you'd be doing growers a big service, because there really isn't any worthwhile info out there other than the one study, which isn't really complete enough to stop me from being curious.

Only if it works for you of course. I'm not actually asking you to do this- just putting it out there. I wouldn't want you to be blown to pieces or burnt alive and die a horrible death because I asked you to dim a lightbulb. That would be bad.

 

[Fuzzy Duck]

I'll double check and document my findings and create a graphic representation over the weekend. I'm glad someone found this interesting!
Thanks Fuzzy Duck!

Yes indeed a superb discovery & got my attention

What surprised my was your DIY added reflector bits which increased lux/ greater concentration to the outer edges of the grow area & in my mind that only means one thing more light for the plants to use = bigger yield in theory.

I'm a lil bit of geek when it comes to reflectors as through various designs you may get light loss from open ended types to closed end reflectors & i may say some air cooled types/designs, what you did with your DIY added wings was to improve a more direct light source towards where it is needed !

Ya deserved some reps for that & for doing the grid reference

 

[Rider509]

No time to get serious about documenting yet, but I did a quick check this am before work.

Pretty impressive jump in light strength for a couple of dollars in materials. FYI, I'd raised the light to work under it.


Sent from my iPhone using 420 Magazine Mobile App

 

[Weaselcracker]

I remembered that there is a lux-meter app for the iPhone so I'll try that.
Besides which- I'm getting the impression that lux meters are quite cheap since quite a few people seem to have them.
So you no longer have to worry about dying a horrible death just to try to answer my questions. I know it was bothering you. Now you can sleep. Thanks anyway.

 

[Nismo12]

I remembered that there is a lux-meter app for the iPhone so I'll try that.
Besides which- I'm getting the impression that lux meters are quite cheap since quite a few people seem to have them.
So you no longer have to worry about dying a horrible death just to try to answer my questions. I know it was bothering you. Now you can sleep. Thanks anyway.

Lux meters are relatively cheap. It's the PAR meters that'll run you a few hundred bucks.

 

[Rider509]

Well then, I need a PAR meter! More toys!


Sent from my iPhone using 420 Magazine Mobile App

 

[rlaboca]

Wht is the optuim light reading fr 600


Magazines Mobile App

 

[Spitz]

I remembered that there is a lux-meter app for the iPhone so I'll try that.
Besides which- I'm getting the impression that lux meters are quite cheap since quite a few people seem to have them.
So you no longer have to worry about dying a horrible death just to try to answer my questions. I know it was bothering you. Now you can sleep. Thanks anyway.

I really want to hear your results!

 

[425jesse]

When I was measuring my lux, when I close my tent door, the reading goes up 6-10%, it was pretty cool. Lots of gain from the door.

 

[Rider509]

So much to learn about lighting! This page does a good job of explaining it.
Horticulture Lighting Metrics - Fluence Bioengineering