@Brotherman074 Lux measures Lumens. Lumens are just all visible light. Lux meters are used for people lighting, but gives a general idea of how bright a light is for plants, just based on Lumen intensity. This can work if you already know the light is for plants.
Plants don’t used the whole visible spectrum however, and the spectrum of light important to plants (400-700nm) is called Photosynthetic Active Radiation (PAR). So technically there’s no such thing as a “par meter”, since PAR isn’t a metric, it’s a type.
Photosynthetic Photon Flux Density (PPFD, or PPF) is the metric used to measure PAR. More specifically, how many photons within a given spectrum hit an area each second. PPFD is changed with a light dimmer, or adjusting the distance to the plants.
The Daily Lighting Integral (DLI), is a number standard for a 24hr period of PPFD. The DLI will change based on lighting schedule. A 12/12 schedule will have a lower DLI than an 18/6 at the same light intensity (PPFD), because the sum of light for the day will be less. This makes DLI the culmination of measurements and is the most complete representation of how much light plants are receiving.
Then you just correlate your light settings based on the meter reading with a chart/graph.
There’s still some conversation around DLI charts, but this one will suffice. You can see how the DLI drops off when the lighting schedule is changed to 12/12. An autoflower staying on 18/6 would hold consistant DLI throughout the grow. Some even recomend increasing the light the day of flip on photos to maintain a constant DLI as well, whereas this chart has the user slowly increase the light intensity over time.
Now for using PPFD readings alone, most recommendations fall in the range of:
200-400 for seedllings
400-600 for veg growth
700-900 for flowering
Hope that helps. Nicky is out on hiatus, but here’s his thread on DLI. It mostly talks about using a LUX meter and converting everything over to PPFD and DLI, but with your meter you won’t have to do any of that. Just set the meter to take the readings you want, and that’s it.