Lighting TOPled The Manual.

[Dr. Frog]

The light meter might help me suss out a light pattern in the tent.

Definitely. On my Galaxy S3 the light meter app is very sensitive and responsive. I can't speak for the accuracy of it's lux readout, as I don't have a proper meter to compare to. However, it does a great job of comparing different light levels in varying areas of the grow space. It's a lot better than relying on my vision, which only says, "It's bright as fuck, everywhere."

Just skimming over the details of lux as a unit I found that it's a measure of lumens over a given area. We know lumens don't tell much about PAR, so I doubt the actual reported values are of much use when measuring LED light, but it does help to compare relative intensities across a range of distances and orientations. As Torched mentioned, it could be useful in identifying patterns of light within a grow area.

For those who are interested, here's the specific app I've been using. There's more on the app store that I'll try out eventually.

https://play.google.com/store/apps/details?id=com.bti.lightMeter

I'll take some readings in my tent and post them here soon.

 

[Dr. Frog]

Alright so I've taken a range of lux readings in my tent under my Mars II. Here's what happened.

Light meter: Samsung Galaxy S3 with app from https://play.google.com/store/apps/details?id=com.bti.lightMeter

Light: Mars II 700 by Topled, regular spectrum, U.S. voltage

Tent: Gorilla brand, 2.5x2'

Procedures: taped a spirit (bubble) level to phone to ensure level readings. LED is also level. Held phone at varying heights in the center of the tent and recorded observed lux readings.

Results:

45" = 16,000 lux
30" = 25,000 lux
20" = 36,000 lux
10" = 75,000 lux
5" = ~200,000 lux *

*(a lot of jumpy readings at 5", no doubt from human error and whichever diode happened to be closest to the sensor... plus it's blindingly difficult to see)




My tent also includes 4 CFL's in work light reflectors at the same height as my panel. These are mostly for my benefit in examining plants, for color balancing. Sometimes I'll switch them on to raise temperature slightly. I took the same measurements with them turned on

45" = 23,000 lux
30" = 32,000 lux
20" = 42,000 lux
10" = 85,000 lux
5" = ~200,000 lux*

*(same as above reading, as being this close to the center of the panel doesn't allow CFL light to hit the sensor)




So switching the CFLs on definitely kicked the numbers up, but remember these readings are in lux, a unit based on lumens, therefore it is difficult to assume that such jumps in lux power actually make a difference in terms of PAR.

All these measurements are done with the tent door wide open, so they don't take into account the amount of light gained by full reflective enclosure. I did do two tests to get an idea of what the reflective material adds.

LED only, 45" with door open = 16,000 lux.

LED only, 45" with door closed = 18,000 lux.

LED and CFL, 45" with door open = 23,000 lux.

LED and CFL, 45" with door closed= 26,000 lux.

So of course reflectivity definitely boosts the numbers. This was pretty rough though as I had to open a tent window to glance at the sensor reading, thus light was lost.

 

[medic grower]

So Dr. Frog u want a 35-50k Lux at the Canopy of your Ladys Thats the Maximum Production. 90.000 is Sunlight on Earth Surface and already Overkill for the Girls. 20" and 42.000 lux seems perfect for them i would go with this height thru Flowering Stage it will not disapoint you.

 

[Darth Vapour]

Very cool work Dr frog, did you take any readings off centre? I'm trying to finalize a decision on my next indoor set up for the fall, 4x2 tent with 4 plants in 3 gallon pots

 

[Dr. Frog]

So Dr. Frog u want a 35-50k Lux at the Canopy of your Ladys Thats the Maximum Production. 90.000 is Sunlight on Earth Surface and already Overkill for the Girls. 20" and 42.000 lux seems perfect for them i would go with this height thru Flowering Stage it will not disapoint you.

I've got to firmly disagree here with your recommendation. Those lux levels you recommended may be great for more traditional light sources like HID, but when talking LEDs, PAR is the name of the game. I don't mean to speak as if you didn't know this or what I'm about to explain already, but it may be useful for those new to LED light sources.

Lumen/lux only applies to applications where human vision is concerned. We can still use lux if we know our light source's spectrum. This is why such recommendations exist for HID light systems for indoor gardening.

As humans, we are much more perceptive to light in the green spectrum.

Here's an example:

3 light sources, all being driven at the same output level or wattage. 3 colors: red, green, and blue. Our eyes would perceive the green source as "brightest." That's just how human sight has developed. Our usual tools like lumen and lux measurements therefore are also more sensitive to green light.

Plants are practically the opposite. Green light is hardly used by plants. You could try to use the green light from the example to grow a plant based on its higher lux rating, but it wont do much without the reds/blues that a plant needs.

So it gets even rougher when you consider how spectrums from various LED panels differ. There are models for veg, bloom, full spectrum, plus each company's own little twist like diodes in white, IR, and UV flavors. Even if all their PAR readings were the same, their lumen/lux readings could vary wildly.

Therefore, it's nearly impossible to recommend adequate light levels in lux from an LED source.

However, you can still use lux readings to get a general feel for the RELATIVE light intensities at different heights/locations/orientations in the grow space. So while the numbers mean practically NOTHING to plants at face value, it allows the grower to compare the values proportionally. Doing so may help to see how their LED lense angles perform, or how their reflective surfaces behave. Maybe you'll even find a hotspot. A hot spot's lux number may not be all that high, but if it's proportionally much higher than other readings in a similar area, you'll know.

 

[Dr. Frog]

Very cool work Dr frog, did you take any readings off centre? I'm trying to finalize a decision on my next indoor set up for the fall, 4x2 tent with 4 plants in 3 gallon pots

Thanks! I took a ton of readings, but I only recorded the ones in the center. I don't know if it's my tent or my light, but the readings were usually very similar at different locations at the same vertical height. They were highest in the center, but not by much. My tent is pretty small, not much larger than the footprint of the LED panel itself. If my grow space was larger, I'd imagine readings further away from the center would start to drop even more. Yay Mylar! [emoji2]

 

[Gloomshade]

Distance off centre amd how that affects the readings is something I'd be interested in too. So you can work out at what height you would get x amount of light footprint

 

[medic grower]

Something Diffrent tha the Lux stuff.... Topled has reduced the Prices on some Units + their Freight Charge for Europe n Uk is really low atm. For all thoose which plan to Buy any stuff over there. Defo gonna order a Unit asap when my Paycheck arrives this coming week. The lil more wait saved me gd 50.- euros hehe.

 

[Dr. Frog]

Distance off centre amd how that affects the readings is something I'd be interested in too. So you can work out at what height you would get x amount of light footprint

I'm out of town at the moment, but I'll take some more lux readings when I get back. The tent is so small, so I'm not too sure it'll be all that different. But if at sometime I'm between grows, I'll take some readings without the tent so we can get an idea of the panel's footprint.

 

[Dr. Frog]

Something Diffrent tha the Lux stuff.... Topled has reduced the Prices on some Units + their Freight Charge for Europe n Uk is really low atm. For all thoose which plan to Buy any stuff over there. Defo gonna order a Unit asap when my Paycheck arrives this coming week. The lil more wait saved me gd 50.- euros hehe.

Nice one! I'm in the states, but just saw on their site that several of their units prices dropped by about $20. Now it's an even better deal! [emoji1]