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[BubbleCat]

So today when stepping outside and the phone screen changed brighness it came to me that someone out there must have developed an app that hops onto the data from the light sensor and interprets it as a rough lux reading.

I wasnt all wrong, the apps I found on Appstore use the camera and at least one of them, "galactica luxmeter" was free but comes with a bit of ads inside.

I will soon investigate the google play store if they also offer this for android phones.

So far a cool thing to play around with and make guesses like where behind the windows or on the balcony, under trees and such plants will get enough light for vegetative growth, or not.

Little advise on lux readings. Besides the phones camera pretty sure being not acurate or precise it id the nature of lux that they only quantify light, but dont qualify it. So if you shone a green light onto it it might read many lux, but a plant woulnt find and use for said light. When it comes to sunlight it always has roughly the same spectrum (dependa a bit on the weather) and you can be sure that around 15k lux you have the minimum for vegetative growth in plants with an average light demand. Somewhere around 80k lux you will find the maximum permissible light for said plants.

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[plantlight]

Thanks for posting this.  Just downloaded an app with digital readout.  I recently purchased an inexpensive light meter for garden use, but I keep it with my gardening equipment and it never seems to be handy when I'm looking for it.  If I can find it, I'll compare readings.

[BubbleCat]

I noticed the back is slightly off my front camera and one goes down to 18 lux the other to 23... fair enough, it seems more precise than i imagined.

Please do so, and tell what kind of device youre using.

[Mangrove]

and here comes Mangrove with this remotely related masterpiece!

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[BubbleCat]

little problem to find out about: with a clear sky, should u focus on zhe sun or keep it out of the image

[plantlight]

Perhaps I should study these a bit more to be sure I'm getting it right.  I have to do some more testing because, although I got some encouraging readings last evening,  I have not been able to get consistent readings today.
Pictures:
1.  The box the inexpensive analog meter came in.  From the description, it looks like everything I wanted and seems to respond to changing light conditions well.
2.  First app I downloaded,Whitegoods,  has calibration ability and when I calibrated it to the analog meter last evening, it seemed to work well.
3. Second downloaded app, Lux Camera, cannot be calibrated, but last evening the first reading looked good.
4. Comparison of analog reading with Lux camera first reading.

I'll try some other apps and update if I figure it out.

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[plantlight]

If I don't have an analog meter or another light reader, is there a way to get a baseline number or a way to calibrate?

I'm using the reference ranges provided here https://en.m.wikipedia.org/wiki/Lux
Hoping to verify both the analog readings and those from an app.  For example, sunset on a clear day is 400 according to the Wikipedia provided range.  I posted my results from last evening in the 4th pic above and got 300 from the meter and 345 from the app.

Post your results so we can compare notes.

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[BubbleCat]

Interestingly the reference states "Surfaces illuminated by" which would mean instead of pointing the camera up to the light source it should be pointed at the plant so it captures the light reflected, if you want the reference table to work.

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[plantlight]

Interestingly the reference states "Surfaces illuminated by" which would mean instead of pointing the camera up to the light source it should be pointed at the plant so it captures the light reflected, if you want the reference table to work.

Yeah, I'm still trying to sort this out.   I'll try what you suggested today.   The table on which the meters were placed for the evening reading is outdoors under a covered breezeway.  Perhaps I was measuring reflected light from the overhang.

[BubbleCat]

On youtube people using the ping pong ball type luxmeter expose the ball directly to the source of radiation.
The question still remains if that method can be tranferred to the camera and if the reference table given can be used in that was, as it states otherwise.

What kind of sensor is on your meter ? We should be able to assume the canera thing is about right so the orientation of both devices that yield the same numbers should be viable.

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[plantlight]

On youtube people using the ping pong ball type luxmeter expose the ball directly to the source of radiation.
The question still remains if that method can be tranferred to the camera and if the reference table given can be used in that was, as it states otherwise.

I tried the the reference table method this morning under overcast scores and got the 1000 - 1300 range on the meter and the lux app.  I then calibrated the whitegoods app to match.  I'm now waiting for a clear skies comparison and evening comparison.  Yes, and I agree for plants, orient toward the light source.

What kind of sensor is on your meter ? We should be able to assume the canera thing is about right so the orientation of both devices that yield the same numbers should be viable.

Not a ball type, a series of three flat sensors. 

[BubbleCat]

I just remembered that I have a bucnh of seminconductive light sensors lying around ... somewhere leftover from constructing a valvetrain test bench, but they are position sensitive devices so i had to run a test to see if they give any usable reference on light intensity.

But they wouldnt be a too good alternative anyways as theyre sacre and a bit pricey.

[plantlight]

I need a new meter.  The low range of the meter seems sensitive enough but the mid and high ranges seem deadened.     Got another cheap meter on order and when I get it, I'll complete the tests and comparisons.

[Urban Elements]

You should be more focused on PAR  reading.
I think Lux is mainly used for photographers.

Food for thought: http://www.lumigrow.com/demystifying-lumens-lux-par/

http://growershouse.com/lights/grow-light-parts-accessories/lumen-par-meters

[BubbleCat]

You should be more focused on PAR  reading.
I think Lux is mainly used for photographers.

I mentioned that before and it is partially true, because:

Sunlight does always havethe same spectrum (might chang a little bit when its clowdy) therefore we can compare the lux readings we get from sunlight and compare it. Cheap.

On the other side, when it comes to artificial lighting you are correct: There is no point in getting lux readings from our LEDs, MHs, CFLs ... and compare them, that would require a $$$ PAR meter.

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