Experience with Mars Hydro FC1500EVO?

Read up on DLI (daily light integral). Light meter of any kind can help. App ppf/ppe readings are not entirely accurate, becuase they are simply converted from klux readings and displayed as ppf, which is going to deviate from light to light based on varying characteristics like CCT. A real quantum meter is probably 300-500 USD and not worth the cost. Important to know that single point measurements are not "PPFD". Readings don't have to be accurate. They jsut have to read consistently, which a 8 dollar lux meter can do or an app. Proportional intensity is the key. assign "100%" to the central reading and probably want to keep edge and corner of coverage at 50% or higher of that reading... minimize that difference, but don't sacrifice overall average doing so. With a 'bar' style frame, 16-18" is usually good when it is properly sized for the tent, but you are using too small of a light for 8 sq ft. Hanging distance is normally about best coverage wall to wall.. You are better of focusing on a smaller size than the full tent unless growing autoflowers. Even then, the size of the frame and spread of light from that frame may not be optimal for 4x2. Ideally, don't want more than 6" out from the sid of the bars, and only 4" out from the ends of the bars. After that more distance will start to impact how much light is getting out to the edges of area of coverage. The umol/s PAR output is supposedly 427, assuming spec sheet is accurate. With this you can calculate 'max' estimated PPFD relative to the area you have focused the light upon and reflective walls enclosing it. PPFd is relative to 1m^2, so merely have to divide 427 by m^2 of area. Whether you are growing autoflowers or photoperiods impacts what you should plant for. Targets: 38-39 target DLI for ambient co2 and at least a loosely controlled environment to avoid extreme VPD conditions. 600ppfd over 18hours or 900 ppfd over 12 hours. You can see it is inversely proportional to hours of operation, as long as nothing else changes, like hanging distance, which could impact ppfd. Some conversions... 8sq ft / 10.764 = .74 m^2 427 / .74 = 577 PPFD 18h operation vege or autoflowers will max out approaching 600 ppfd: So, that light at full power is fine as far as photon production for autoflowers in a 4x2, or a dedicated vege area on 18h operation. The bigger problem will be the size of the light frame relative to the 4x2 area as stated above... It will be too weak for 12hour operation of flower phase in a 4x2. ~600ppfd over 12 h is only 25.9 DLI. (577 falls negligibly below that). It "can" flower a plant at ~25 DLI but yield will suffer for sure compared to ~35-40 DLI. It won't be a catastrophe at 25.9 DLI, but it will definitely hurt the yield (grams/sq ft) and impact density of buds. Mars suggests 2.3' x 2.3' (5.3 sq ft). This seems wiser. This is just under .5m^2 and turns that PPFD into ~854, which is good enough for 12 hours... approaching 900. So, unless you are growing autoflowers, stick to a smaller footprint in that tent with this light, because as you get to 12 hour needs, the light can keep up. If you follow that recommendation, run the light at roughtly 67% power over 18h, and use a light meter to best focus (hanging distance) it on that ~5.3-5.5sq ft area inside the tent. These are intitial targets that will require minimal adjustment based on the growth you observe. That is the verificiation -- internode length. If it stretches, needs more. If it remains too tight in new growth, needs less. The growth pattern is the culmination of all your environmental factors that equate to how much light you can provide per day. Except in very tightly controlled environment, you will see variance in how much light you can provide compared to other gardens or even due to local seasonal changes. No matter how good the initial suggestion is, some adjustment is likely and you may even need slightly different settings at different times of the year. No matter the suggstion, resulting growth dictates what is correct. it accounts for all the local variables. temp, rh, vpd, ambient co2 in atmopshere are the primary variables that will equate to max dli you can provide without damaging the plant. 20-25 DLI is a minimal to form 'some' decent buds. 35-40 DLI should max out ambient CO2 conditions. 1300ppm co2 and tightly controlled climate? 55-60 dli might be the target. I've never supplemented co2, so less defnitive suggestion on that.