So this meter tells you what Carcass, how many watts you're pulling from the wall? Why is that need-to-know info?
Say I'm using a light meter of some sort to regulate the light my plants get. And let's say my desire is 500 par and I adjust the lights (height or intensity) to make it so. Then I use a kill-a-watt meter and find that my, say 100w light, is only pulling 85 watts. Then what? As long as I'm getting 500 par to the plants why would I care? Are you using wattage targets during various stages of your grows?
I wouldn't use Photone.
I've tested it twice, once when it was called "Korona" and I tested it against a Kind blurple. It could not produce a reading. At the time, growlightmeter.com didn't specify the paper weight so I tested 20, 22, and 24 pound papers and sent my test results to the programmer (I've been a software engineer for 30+ years). He didn't have an answer for why Korona failed but he gave me licenses for all light sources. I bought an Apogee because I didn't believe that light meter + using a factor was valid.
About a year later I tested Photone again and measured it using my Apogee. Photone read 16% high, at all dimmer settings. It's good it was consistently high but 16% high? I was using an iPhone xsMax with the prescribed weight paper.
There are advantages to Photone but accuracy is not one of them unless the users' phone + light setting has been shown to be accurate. The problem — how do I know if it's accurate?
After Photone crapped out on me, I decided to look into lux meter + conversion and that's the route I recommend. Per above, if your iPhone + Photone is known to be accurate, good on ya. If not,I recommend a Uni-T light meter and then use the conversion chart in the document I've attached.
One of the weaknesses of using an iPhone is the need for a diffuser. In the programming world, that's called "kludge". "hack" is a trendy phrase but it's not a hack. The diffuser is a hit and miss solution to a weakness of the sensor in a mobile phone - it's designed to meter light coming directly into the sensor. In comparison a light meter and a PAR meter have a parabolic cover over the sensor.
Again, it might work, it might not but for $32 a Uni-T light meter is about as (in)accurate as my Apogee.
Photone on Android? If you can calibrate it to a known good source, good. If not, I wouldn't touch it. In my correspondence with the programmer, he lamented the problems that they have with widely varying quality levels of the huge number of Android devices. That is one argument for Apple - they control the platform so they will tend to have more consistent results (I'm a former Apple employee — no biggie, they're another huge company, just sclerotic in less visible ways than other companies).
I like using an Apogee. I use it daily and run my grows pretty close to 1kµmol. I can do that with a Uni-T (I have the both the Bluetooth and the non-Bluetooth models) but I wouldn't do it with Photone.
The factors in the PDF are from lights I own or the source for the factor is cited. Chilled and HLG publish a lot of data so, anyone using those lights is getting good info. If a given light isn't listed, 0.015 will get you really close. Add a little if you've got a light with far red (0.0153 or 0.155) , drop a little for a light like the Vipar XS1500Pro which has a lot of blue (0.0145?)
To my way of thinking, I'd rather spend $31 and get something that's 5%± (that's the Uni-T spec for that meter) + the slop in the factor than use a product that I have no idea if it's accurate and then wing it from there.
BTW, the three results I've seen from Photone vs a lux meter have been the Photone reads high. I can make the argument that being high is OK (pun intended) because by that builds in a safety factor. That's important to some people. My preference is steel on target in the first volley.
The other two are looking GOOD !
