This is my second grow ever. This is what I am using as a reference point. Other than the DLI schedule because it seemed my plant could handle more than what was listed there.
Best source I've found for VPD is
here. Pulse was the first generation of VPD hardware that I used. Inkbird was next and I've settled on AC Infinity.
AC Infinity has an excellent IR gun because it can be calibrated and you can change the emissivity factor. The latter can make a small difference. Overall, VPD is really keeping things between the guardrails.
The second upload is just general info. You can't go wrong with those values but there's a very wide range between those temp and RH bands. I'm (was) a software engineer for 30+ years before which I was an artillery officer so I'm used to process and precision.
The growlightmeter.com graphic is complete garbage. I tested Photone years ago, when it was called "Korona", and it was pretty inaccurate but you
can get accurate readings off of it if you're using a diffuser and it you hold the phone in the right position. To my thinking, I'd advise growers to get a lux meter because it's a light meter so, over time, I believe you will tend to get better results than if you're using a camera with a strip of paper over the lens. A lux meter is $25± and they're accurate to 5%±. There is some possibility for inaccuracy if you don't use the right conversion factor but I've written a document that provides some info on that and, overall, you can get as close as is needed.
OK, why did I call the GLM graphic garbage? My bias is that I'm a high light grower so ramping up slowly the way he recommends is just not my cup of tea but I understand the mindset that supports the slow ramp up and it works for a lot of people. Having said that, there's nothing anywhere that substantiates dropping PPFD when you go into flower.
Last time I checked, GLM had a link to another site to provide more information for what they were recommending but, when I clicked on the link, I got a 404-Page not found error.
There's scads of research re. light levels using LED's and many growers on this site are feeding their plants well but that means completely disregarding the silliness in what GLM.com has posted.
Interestingly, the folks at the website for autoflowers is firmly in the "600µmol is plenty for flowering". The information on Migro.com is also not evidence-based and that's strange because Shane, the owner of Migro, has interviewed Bugbee and is fully aware of how much light cannabis can use but his recommendations are, in many ways, simply not valid.
Virtually all of the cannabis sites use the "legacy light levels" of 300 in seedling, 300-600 in veg, and 600+ in flower. Those are not based on what the plant can used but are based on the light output from HID lights those being MH and CMH in veg and then HPS in flower.
HID is obsolete technology having been surpassed by LED's. The recommendations for light levels by the most popular vendors have, over about the past year, fully embraced what "the research" has been telling us for about a decade but habits and attitudes are sometimes hard to change.
Unfortunately, a lot of growers follow the guidance at GLM and end up getting a "modest" crop. If you search for my postings here and on another web site where I'm a member you'll see that I'm fairly outspoken (cough, cough) about this—it pains me to see growers put their heart and soul into something for three or four months and end up with "modest" yields when they could be getting so much more for their efforts.
</soapbox rant>
If your plants are doing well at 900, that's excellent. The diagram below is a good checklist of things to set up in a grow environment. I've used it more than once since I started growing and found it to be really helpful. Since I'm a process person, I approach the growing problem by optimizing one aspect of the grow environment at a time. to me, it's just a process of removing the variables and, when you do, you get a shitton of weed. Perhaps that graphic can help.
I have had a hard time getting my EC above 1 unit my last 2 waterings. Watering before last got EC up to 2. Hand watering. But not getting nearly as much runoff as I was.
Soil, eh? That's all "magic" to me, I drown my roots.
Perhaps a soil grower can poke their nose in here or you can post something in the "beginner questions" section for some advice. I'm not up on the techniques needed for soil .