These are a couple articles I ran across after my brother talked to me about the Lux light meter that is on my Samsung Galaxy S3 smart phone. Some very interesting stuff. I will not take credit for the information content, just bringing it here.
A link to this post samsung galaxy s2 + s3 built in LUX meter - BreedBay
" Just wondering how many people with either a galaxy s2 or s3 have found there built in digital , light LUX meter ?
to access it dial *#0*# to enter the hidden menu, you will be faced with 13 icons to test various things such as screen , speaker,camera , the interesting one is the sensor icon,
press it to enter menu and display info on gyroscope,accelorometer,magnetic sensor, click on light sensor to display the LUX value on screen, it uses the the sensors next to the front facing camera to detect light levels, pretty accurate too !
I would imagine every so called "Smart" phone has one of these meters and a way to access it.
now everybody can see how much light there plants are receiving and how to optimize there reflection to suite there need"
ANOTHER ARTICLE.
PAR: Photsynthetically Available (or Active) Radiation. All radiation with a wavelength of 400nm to 700nm.
PPFD: Photosynthetic Photon Flux Density. A way to measure PAR. It's the number of photons of light falling on a given area in a given amount of time, and its units are micromoles per meter square per second (µmol m-2 s-1).
Lux: A measure of illuminance, measured in lumens per square metre.
Now, a given light source will produce a certain amount of its output as PPFD. This amount can be related directly to illuminance by way of a multiplier, and, importantly, is constant for each source type*.
Here are the multipliers to convert illuminance in Lux to PPFD for some common light sources:
Code:
Source Multiplier
Sunlight 0.0185
Fluorescent (Grolux) 0.029
Metal Halide 0.0141
Fluorescent (865/840) 0.0135
High Pressure Sodium 0.0122
Figures provided by Apogee Instruments.
So, we can multiply the Lux value by the multiplier in the above table to find the PPFD in µmol m-2 s-1.
Worked example:
Code:
60 cm x 60 cm space (0.36 m²)
250 Watt HPS lamp (33,200 lumens)
Lux = (total lumens) / (total area in square metres)
= 33,200 / 0.36
= 92,222
PPFD = Lux x factor
= 92,222 x 0.0122
= 1,125
What level of PPFD is good? I don't know, but I imagine that, like everything in this game, "More!" is probably the answer**. The proper information is almost certainly out there though.
As a reference, direct sunlight at midday, with a Lux value of about 100,000, will provide a PPFD of around 1,850 µmol m-2 s-1.
There's also another measure of PAR, and that's YPF (Yield Photon Flux) PAR. It's weighted more to the plant response curve, and the red end of the spectrum, than PPFD and so is probably a better measure for growing purposes, but I don't have any conversion factors.
Finally, here's a table showing the PPFD for a few lamp types and sizes:
*For suitable values of 'constant'. It's mostly constant, but may vary with specific or specialist lamps.
**There probably is a maximum upper limit, and the law of diminishing returns will probably start to take effect before that limit is reached.
A link to this post samsung galaxy s2 + s3 built in LUX meter - BreedBay
" Just wondering how many people with either a galaxy s2 or s3 have found there built in digital , light LUX meter ?
to access it dial *#0*# to enter the hidden menu, you will be faced with 13 icons to test various things such as screen , speaker,camera , the interesting one is the sensor icon,
press it to enter menu and display info on gyroscope,accelorometer,magnetic sensor, click on light sensor to display the LUX value on screen, it uses the the sensors next to the front facing camera to detect light levels, pretty accurate too !
I would imagine every so called "Smart" phone has one of these meters and a way to access it.
now everybody can see how much light there plants are receiving and how to optimize there reflection to suite there need"
ANOTHER ARTICLE.
PAR: Photsynthetically Available (or Active) Radiation. All radiation with a wavelength of 400nm to 700nm.
PPFD: Photosynthetic Photon Flux Density. A way to measure PAR. It's the number of photons of light falling on a given area in a given amount of time, and its units are micromoles per meter square per second (µmol m-2 s-1).
Lux: A measure of illuminance, measured in lumens per square metre.
Now, a given light source will produce a certain amount of its output as PPFD. This amount can be related directly to illuminance by way of a multiplier, and, importantly, is constant for each source type*.
Here are the multipliers to convert illuminance in Lux to PPFD for some common light sources:
Code:
Source Multiplier
Sunlight 0.0185
Fluorescent (Grolux) 0.029
Metal Halide 0.0141
Fluorescent (865/840) 0.0135
High Pressure Sodium 0.0122
Figures provided by Apogee Instruments.
So, we can multiply the Lux value by the multiplier in the above table to find the PPFD in µmol m-2 s-1.
Worked example:
Code:
60 cm x 60 cm space (0.36 m²)
250 Watt HPS lamp (33,200 lumens)
Lux = (total lumens) / (total area in square metres)
= 33,200 / 0.36
= 92,222
PPFD = Lux x factor
= 92,222 x 0.0122
= 1,125
What level of PPFD is good? I don't know, but I imagine that, like everything in this game, "More!" is probably the answer**. The proper information is almost certainly out there though.
As a reference, direct sunlight at midday, with a Lux value of about 100,000, will provide a PPFD of around 1,850 µmol m-2 s-1.
There's also another measure of PAR, and that's YPF (Yield Photon Flux) PAR. It's weighted more to the plant response curve, and the red end of the spectrum, than PPFD and so is probably a better measure for growing purposes, but I don't have any conversion factors.
Finally, here's a table showing the PPFD for a few lamp types and sizes:
*For suitable values of 'constant'. It's mostly constant, but may vary with specific or specialist lamps.
**There probably is a maximum upper limit, and the law of diminishing returns will probably start to take effect before that limit is reached.
