Cheap Par Meter Hack
- Thread starter S4m
- Start date
Check this MIGRO article instead - apparently the Photone smart phone app is pretty accurate.
Edit: Here's the corresponding MIGRO video:
Edit: Here's the corresponding MIGRO video:
What stage of growth are you in (seedling/veg/bloom), and what's your light cycle (# hrs per day - e.g., 18/6, 20/4, 24/0, etc)?
1200 is on the upper level of typical ranges, but not overly excessive (unless maybe for seedlings). If they've been doing well otherwise, than I wouldn't worry. For LEDs, what's usually called "light burn" from excessive light levels is typically just nutrient / VPD / water issues that develop because the plant is using more light and growing faster.
For reference, 2000 PPFD is max noon summer sunlight, and 1000 PPFD is typical average direct summer sunlight.
Growth-wise, I've seen recommendations of ~300 PPFD for seedlings, ~800 PPFD for veg, ~1000 PPFD for bloom. Those are usually based on the fact that the efficiency of photosynthesis and transpiration can start to decrease around ~800 PPFD, not because more would necessarily be bad. The plants can still make use of the extra light, and as far as total yield is concerned (which is what we ultimately care about), cannabis plants don't typically "plateau" like other plants.
Technically, high light levels (1000+ PPFD) can cause various "photoinhibition" processes in cannabis, but there's not much research to say whether those processes are good or bad, what's too much, what's best, etc. For example, light levels may have a slight effect on final terpene and cannabinoid profiles, but those can often be affected just as much by spectrum differences (UV vs. no UV, etc) than by intensity levels (1000 PPFD vs. 1500 PPFD, etc).
Note that the other metric is DLI (Daily Light Intake) - which is basically (PPFD) x (Number of Seconds Lights Are On Per Day) / (1 Million). So, 1200 PPFD for 18 hrs would be 77.6 DLI. "12 Hours of summer sunlight" would be 30 - 45 DLI and "max outdoor summer light" being about 60 DLI.
One benefit of autoflowers is that they can use longer light cycles than photoperiods, and so get the same DLI at lower PPFD values. You could dim the lights to save on electricity / reduce heat, or raise them to get better / more even coverage across the space - but again, if your plants have been doing fine otherwise, there's no real need.
1200 is on the upper level of typical ranges, but not overly excessive (unless maybe for seedlings). If they've been doing well otherwise, than I wouldn't worry. For LEDs, what's usually called "light burn" from excessive light levels is typically just nutrient / VPD / water issues that develop because the plant is using more light and growing faster.
For reference, 2000 PPFD is max noon summer sunlight, and 1000 PPFD is typical average direct summer sunlight.
Growth-wise, I've seen recommendations of ~300 PPFD for seedlings, ~800 PPFD for veg, ~1000 PPFD for bloom. Those are usually based on the fact that the efficiency of photosynthesis and transpiration can start to decrease around ~800 PPFD, not because more would necessarily be bad. The plants can still make use of the extra light, and as far as total yield is concerned (which is what we ultimately care about), cannabis plants don't typically "plateau" like other plants.
Technically, high light levels (1000+ PPFD) can cause various "photoinhibition" processes in cannabis, but there's not much research to say whether those processes are good or bad, what's too much, what's best, etc. For example, light levels may have a slight effect on final terpene and cannabinoid profiles, but those can often be affected just as much by spectrum differences (UV vs. no UV, etc) than by intensity levels (1000 PPFD vs. 1500 PPFD, etc).
Note that the other metric is DLI (Daily Light Intake) - which is basically (PPFD) x (Number of Seconds Lights Are On Per Day) / (1 Million). So, 1200 PPFD for 18 hrs would be 77.6 DLI. "12 Hours of summer sunlight" would be 30 - 45 DLI and "max outdoor summer light" being about 60 DLI.
One benefit of autoflowers is that they can use longer light cycles than photoperiods, and so get the same DLI at lower PPFD values. You could dim the lights to save on electricity / reduce heat, or raise them to get better / more even coverage across the space - but again, if your plants have been doing fine otherwise, there's no real need.
It works you should get one of the models he lists and match it to the correct conversion factor. Mine is the yellow one in the pic above and the conversion is lux × 0.022 I also have a different model that reads way different from these with a conversion of 0.015 I think. What im getting at is these meters aren't all the same so Nox Vidmate VLC definitely order one of these that he's working with.
Last edited:
I got the Uni-T BT and use the PPFD android app https://play.google.com/store/apps/details?id=com.homestudio.ppfdmeter&hl=sv&gl=US
I used to work as a comercial photographer so I have a color temp meter from the old film days laying around
Measured my Mars Hydro TS serie and got 3550 Kelvin and the app only had 1 option for 3500K and that was low CRI 3500K so I contacted the app developer and had a really nice convo where he recommended to use that option.
Since Shane @ Migro recommended one guy asking about quantom bord style light with 3k+5k and red diods what conversion to use he recommended the Uni-T lux value x 0.017 for PPFD.
I fixed my Uni-T at a place where I got 40 000 lux and the app should in this case show 680 PPFD ( 40 000x 0,017) but it was lower so I calibrated lux meter settings in the app to + 5% and then I was spot on.
It's not going to be 100% but I think I got it closer by doing this.
I used to work as a comercial photographer so I have a color temp meter from the old film days laying around
Measured my Mars Hydro TS serie and got 3550 Kelvin and the app only had 1 option for 3500K and that was low CRI 3500K so I contacted the app developer and had a really nice convo where he recommended to use that option.
Since Shane @ Migro recommended one guy asking about quantom bord style light with 3k+5k and red diods what conversion to use he recommended the Uni-T lux value x 0.017 for PPFD.
I fixed my Uni-T at a place where I got 40 000 lux and the app should in this case show 680 PPFD ( 40 000x 0,017) but it was lower so I calibrated lux meter settings in the app to + 5% and then I was spot on.
It's not going to be 100% but I think I got it closer by doing this.
Similar threads
