This almost sucks

Hi all,

been sampling my white widow from last grow tonight. I am a light weight and only do every month or so… but i just love to grow.

And my latest quest is measuring PPFD… at a single point let alone an area of one meter squared.

I ran across some advanced equations (way above my head so to speak) that will convert LUX to PPFD accurately. I have spent many hours working with this authors example and all i can say is he nailed it! I was able to work his math with a spreadsheet and nailed his results to within .0003 decimal points. Could be coincidence, but I really do think he nailed it.

the part that sucks is the most important part, LUX meters have either end of the spectrum heavily filtered to match the way people see so we loose resolution for the way plants see, the deep reds and blues.

I cant wait to spend the next few weeks digesting why this math worked so well!

If you want to research it do an internet search of the of this brilliant fellow: look this up:

Photometry and Photosynthesis


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You’ll love this thread:

There’s many on here using the info to truly push the reefer to the max.
Along with the far red, uva, and uvb threads you can’t go wrong… Tons of knowledge here.

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excuse me?

your kidding… a smart phone?

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I have measured the app against a $500 apogee meter and the readings were very close. The light sensors on newer phones have gotten really good.


@AxisCat I have checked against my much cheaper quantum sensor as well… Even the camera on my Surface Duo v1… Which is known for its crappy camera… Checked out.

I use it for the dli occasionally… I had already owned my quantum sensor and created separate veg and flower tents for their specific needs…
So my lights and environments are dialed in and know when and how much to adjust.

You should look into bruce bugbee on youtube i think you’d really like his videos

I have an Apogee PPFD meter. I’ll have to download Phototone anddo a comparison too. Would be an interesting experiment.


I know @Hellraiser compared his results too. Also very similar readings.

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Conversion factor changes depending on what/how wavelengths are represented. Not an exact science because one brand 3000k may be slightly different than another brand 3000k. 3000k 70cri, 3000k 80cri, 3000k 90cri are all different. But if you get semi accurate conversion factor is reasonable to use.

off the subject, I cannot find a place to post anything. I can reply but not post WTF

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You gain the create post privileges by reading, liking, commenting. Your comments will be limited for the first 24 hours. These are measures put in place to prevent spam bots from flooding the forum.


i finally was given posting rights, didnt realise it took time. thanks for your kind words. Budme


I was unthrottled last night at @8:34 pm. New to the site too.
I feel(t) your pain…

Thanks for your respons. Growing indoors can be extremely technical or easy depending on what you are growing and desired outcome. I believe forums like this are a rich resource of info, and you have to take with some caution. Thank you again for your info, it was spot on. Grow in peace my friend.

I apologize for posting and disappearing the other night… I have a lot going on at home. I appreciate everyone’s replies. I am going to keep plugging away at this until I hit a brick wall or get bored and move on to another project… I will follow up with any results I come up with

Go to the Migro channel on you tube, Shane has done a video on this question. He’s taken the top 4 Amazon LUX meters and provided given a conversion number for each. He’s done all the hard work. I use a $25 LUX meter and, using his formula, I can get my PAR measurements to within 50 or so of an Apogee.

PS yes, he also has a video for using a phone camera, he’s devised a system so that you can get reasonable accurate numbers from that too.

Check out his channel y’all, he’s a godsend to us budget growers.