Puis-je faire confiance en mon smartphone pour mesurer de PPFD ?

I don't think mine is that far out, maybe says the light is a little stronger then it actually is.

That's why calibration is important. Even Apogee's quantum meters need regular recalibration. In a video, Bugbee talk about a tool you can use to get sunlight metrics for where you live, so you can calibrate your equipment on a clear day. I'm currently trying to find this video. 😋

I use the photone app and have used it for quite a while. I have not Calibrated it so its been a bit trial and error over the last few years but I have found the readings my plants like throughout there life span. Just hope when I change my phone the readings will be the same.

i have had different results with different phones depending the quality of the photo sensor it can be accurate enough or totally funky.

For those who are coming in after the battle (literally), the original presentation is in the first comment all the way at the bottom of the page (GD doesn't allow for much text in the question titles). ^^

> The emitted luminous flux (in lumens) of an LED lamp is a transmission quantity. The illuminance (in lux) describes the luminous flux received and is therefore a reception quantity. Fun fact: in this sentence, you can replace "emitted luminous flux (in lumens)" with "PPF," "The illuminance (in lux)" with "PPFD," and "luminous flux" with "irradiance," and it still works. And I thank Polyphemus here for debunking himself for once. ^^

> Questions is like a separate part of the site for whatever reason. My guess is one dev (or one team) make GD in the first place, and later someone else added the Grow Questions sections. :3

> and i'm going to ensure that by blocking you It don't work: i've blocked you days ago.

Polyphemus, you're repeating yourself. Lux is a measure expressed in lumens per square meter per second. It's exactly the same as between PPF and PPFD… You really have to be stupid to stab yourself in the foot like that. I presented well-supported arguments, you just keep shouting without citing a single viable source. End of story.

angus, i wont' reply to you ever again.. and i'm going to ensure that by blocking you

due to inverse sqare law in effect with lights... a matter of 6 inches can greatly impacat resulting DLI... light spreads out quickly. you can take a lazy approach.. or you can fine-tune it. each to their own on that. you want to waste money (electricity) .. that's your choice.

lux and lumen are 1:1 so it doesn't fucking matter except to nit-pick. "Difference between lux and lumens The emitted luminous flux (in lumens) of an LED lamp is a transmission quantity. The illuminance (in lux) describes the luminous flux received and is therefore a reception quantity." it's measuring the same exact thing the difference is transmission vs reception. irrelevant. light meters measure klux.. not lumens. you jsut made up a useless argument again.. go re-read. never said anything about only in 1 m^2... i but it is relative to 1m^2 .. that way you can compare DLI in a 4x4 to a 3x4 and it means the same thing.. and in this case PPFD too. your cmos censor explanation is narrow-sighted and missing sevearla important other foactors at play. A phone is still shit at measuring umol/s any which way you slice it. the apps even say so if you read the fine print. DLI and PPFD are not the same thing and part of what you obvisouly do not get... lol.. ppfd is a factor in cacluting DLI.. ppfd can be comapred accros different sized areas but not different hours of operations. DLI can be compared apples to apples across both contexts.. inherently different things even if one is a factor of another. One is a rate of photons per m^2 the other is the total moles of photons applied per day.. FFS it's in the equation. just fucking read it... are you trying to be obtuse? i'm not replying to you anymore.. you either are fuckign ignorant beyond help or you are purposefully spewing nonsense for a response. also, your perception of how much your respect means to be is very over-bloated, lol.. your repsect is nothing. you are one person that clearly is missing more than half of the needed knowledge to udnerstand this stuff, lol. your superficial understanding and narrow-sighted focus is laughable. you are objectively and verifiably wrong. no respect from an obstinate person that refuse to do a little reading is no loss.

@Organoman no no no, it's not a question: I'm presenting studies that explain that a photo sensor can perfectly be used to measure light intensity. I'm just trying to reassure beginners by reminding them that it's a viable tool, despite Polyphemus's petty bourgeois behavior, who clearly can afford an overpriced tool that we will only use a few times. You should go read the first comment all the way at the bottom. ^^

There is no controversy on this site. Just a bunch of morons that know fuck all. Oh that's all of you.

Keep your light at the recommended height the manufacturer gives........your planrs will be fine and will not notice or complain. Tiny, tiny details make microscopic differences that you will never, ever notice!

OMFG! The automatic translator on GD is so bad. > < 'q

> You still don't distinguish between PPFD and umol/s correctly. Coming from someone who clearly can't tell the difference between Lux and Lumen and has repeatedly proven they can't calculate areas correctly, I find it endlessly comical. > To accurately convert from Lumens to umol/s requires […] Lux. The application takes the value received in Lux and converts it to PPFD using the type of lighting specified by the user to apply the associated conversion factor in the software's database. Although I've said several times that I appreciate being corrected when I say nonsense, one must still learn to read. > ppfd is not a single point measurement. it is the total rate of umol/s PER meter-squared. You'd need many, many measurements from the entire area, then average them together to get an idea of PPFD As I mentioned earlier, you clearly have issues with the concept of area. Although PPFD is a measurement expressed in mol per square meter per second, that certainly doesn't mean it's a value that can only be measured over an area of one square meter. If we follow your reasoning, then we can only measure speed in Km/h by moving for one hour. However, it is perfectly possible to measure a value over a smaller area (or distance) and then extrapolate the results. That's the principle of a unit of measurement. Honestly, I wouldn't want to be in your head when faced with the coverage map of a light fixture. It must be hell in 2D. > The "PPFD" (wrong terminology if a single point) it reports is suspect for several reasons you simply cannot avoid. the wide angle of light entering the lens is a big problem too. It causes wildly inflated lux readings, for example. Actually, I'm talking about a CMOS sensor, and if I take the time to explain that it's a surface covered with photosensitive sensors, it's to highlight the fact that it's a surface and therefore it will measure values over the entirety of the surface. Moreover, since the size of the sensor and the angle of view of the optics are known values, the manufacturer (Sony in the vast majority of cases) takes these values into account to return a measurement in Lux through the API. Now, if you don't want to trust the skills of Sony's engineers… Furthermore, photo optics receive an anti-reflective treatment precisely to prevent light from bouncing around and skewing the sensor measurements. > Also, DLI is what matters.. not PPFD. It's absolutely the same thing, just on a different time scale. And both are important. And since you only seem to try to discredit the validated research on which I base what is supposed to be a small article for beginners and not for pseudo-nerds who are just stroking their egos, I'll just remind you that in the debate about flushing, I vigorously criticized AutoflowersMachin because he refused to consider the unverified study you presented as an absolute fact to support your claims. So I'll make the same remark to you: Your inflated ego makes you stupid and blind to the point where you quote scholarly names but refuse to consider serious studies when they don't align with your views. It's a pathetic behavior, but at least it allows us to understand that your strategy consists of dispersing information in your overly long, boring, poorly written, insulting, and poorly sourced explanations, in order to make everyone believe that you master a subject that at best you struggle to explain, and at worst don't understand and on which you just embellish. I'll be frank with you: not only have you completely lost my respect, but I refuse to continue playing your stupid game as long as you have nothing but whines as arguments.

heck, "max" dli changes every day in every garden that doesn't have precise controls over it's environment. you potentially need something a little differenet each day..

You still don't distunguish between PPFD and umol/s correctly. you seem to use them interchangeably and you don't understand the difference between measuring Lumens and photons. this is part of the problem.. you incomplete understanding. To accurately convert from Lumens to umol/s requires the SFD, or spectral flux density, of the light in question. A camera lense definitely does not have this capability. Therefore, all they can do is use a one-sized-fits-all conversion factor that could have enormous error for some people and less for others.. but some error for all except for the lucky few whose light directly matches whatever conversion factor they whimsically choose to use. This is incontrovertibly true... it is fact. Cannot deny it. mathematical certainty. ppfd is not a single point measurement. it is the total rate of umol/s PER meter-squared. You'd need many, many measurements from the entire area, then average them together to get an idea of PPFD.. the more points of measurement, the more accurate the guesstimate will be. It is a time-intensive and focus-intensive operation. if not measuring from same exact distance at each point and perfectly level each time you do measure, it's going to contain human error as well as rounding errors due to possible low resolution of measurments (how many across canopy and evenly distributed poitns on top of that). Lumen meters and phone apps are effective at giving you proportional intensity. That is useful. The "PPFD" (wrong terminology if a single point) it reports is suspsect for several reasons you simply cannot avoid. the wide angle of light entering the lense is a big problem too. It causes wildly inflated lux readings, for example. Also, DLI is what matters.. not PPFD. PPFD is an incomplete picture when assessing how much energy you are providing per day (DLI). A single measrument will be of umol/s of PAR. you need trial and error based on observation of plant growth to fine-tune power, distance of light etc, regardless. A more accurate guesstimation of DLI provided will definitely shorten this learning curve, but totally uneccessary to achieve the same goal. It is helpful in comparing relative intensity of various locations in canopy in order to more evenly distribute light. That's it. Calculating DLI from hours of use and light's specs is a faster and more accurate process given basic common sense. Can you dream a context in which it is not? sure, but it would be a context that wouldn't match any rational garden space. reading lux does not mean it can read umol/s in an accurate way or else there'd be apps available that don't convert from lumens. That method is inherently inaccurate given the context. The apps that come with a meter and can effectively convert lumens to umol/s do exist, but you need a bluetooth/wifi probe to do so. those apps aren't the free ones, either. Yeah, you can accurately measuer lux, but that isn't what matters. I'd still argue a 10 dollar light meter is a better way to go because it is far more directional than a wide angle lense. you'll see those meters measure lux much lower than a phone app. My diy lights burn the shit out of plants at 32-35klux over 12 hours of operation, for example, and i see people with readings of 65klux from their phone apps with lights that pale in comparison in quality/power. That's with a real light meter.. not a phone app with inherent issues beyond the physical chip you mention. no one said don't use a smartphone app.. they merely put it in proper perspective of what its real capabilities are. you just made up soem weak argument that was never used (scarecrow logical fallacy). proportional intensity is useful.. but don't lie to yourself that your phone accurate can give you a PPFD measurement or umol/s LOL... it cannot beyond some wide ranaging +/- 10% or more error. the consitency of it's measurement is what is useful. they number may not be right, but if you find your corners or edges are 50% of readings in center, you know your umol/s is also 50% at corners and edges compared to center... even if you don't know exactly what that umol/s is in either spot. it can help you even out canopy.. choose a more effective hanging distance etc. regardless, you need trial and error observing plant over long periods of time to know if oyu have your light that is providing max DLI -- i.e. you amp up until you have damage, then you back off to the point where no damage occurs over long-term. sometimes light damage takes 2-3 weeks to see the symptoms if only a small bit off vs off by a large amount. local enviornmental variables make any DLI suggstion a ballpark concept, regardless. There is no 'single" DLI recommendation because what is optimal will vary quite a bit from 1 garden to the next.

"That migro guy from youtube" the name is Shane Torpey. ^^ And if I refer to the studies I've taken the trouble to link to, in fact even uncalibrated the results are fairly accurate. But yes, it's better to calibrate the application and it's really not complicated if you have access to precise measurements for your lamp model.

A CMOS sensor, which has equipped the majority of digital cameras since 2000, is a surface made up of thousands of photosensitive cells that convert photons into electrons. Each pixel in a photo is generated from 4 photosensitive cells, covered with red, green, and blue filters (with green being doubled), forming a matrix that allows for the interpolation of the pixel's RGB value. If your smartphone's front camera is advertised as 3Mpx, it means that the sensor is composed of at least 12,000,000 of these photosensitive cells. All of this is protected by a low-pass filter, which filters out IR frequencies, making the CMOS a tool perfectly capable of measuring the quantity of photons strictly within the PAR, perceived across its entire surface. In fact, two studies from 2013 and 2017 confirm that it is perfectly possible to use a webcam or the photo sensor of a smartphone, provided that the pixel value is converted to black and white, calibrated, and results are obtained that are sufficiently precise to be used by a hobbyist or even a pro. https://www.researchgate.net/publication/261031459_Development_of_a_webcam_based_lux_meter https://www.researchgate.net/publication/317596937_Smartphones_as_a_Light_Measurement_Tool_Case_of_Study On Android devices, the light sensor value is calculated by the photo module or driver and is retrieved directly in Lux via the API: https://developer.android.com/reference/android/hardware/SensorEvent#values (see Sensor.TYPE_LIGHT) The mobile application, whether it's PPFD Meter or Photone, simply converts this Lux value to PPFD and offers various presets to use the coefficient most suitable for the type of light you are using. It is also possible to correct the drift by calibrating the sensor using the values that testers or the manufacturer have recorded at full power at a given position and distance from the light fixture. By the way, I would also like to highlight this study from 1993 conducted by the Department of Plants, Soils, and Biometeorology, Utah State University, co-signed by the highly esteemed Bruce Bugbee, which demonstrates that Quantum Sensors measuring PPF and YPF tend to return erroneous results in the presence of red LEDs. Given that the vast majority of horticultural fixtures nowadays are equipped with red LEDs, this is a significant point. https://journals.ashs.org/hortsci/view/journals/hortsci/28/12/article-p1197.xml In conclusion, as an amateur grower, it is therefore perfectly possible, and even recommended, to use your smartphone to get a fairly realistic estimate of the PPFD, without needing to spend money on a professional device, which would be more useful and robust for outdoor installation.