I am the owner of a growing facility plus a lot of marijuana growers want to guess about my light rooms for growing, but the lights when growing cannabis can be tricky. A huge amount of it depends on the age of the plant, the temperature you want and what your growing facility looks like, however for example, smaller cultivation operations entirely should consider fluorescent lights. They are cheap, don’t produce a lot of heat plus should be inches from the plant, and you can have short ceilings and very little space however still have a healthy crop. Young plants especially do well with the fluorescent. There are HID or high intensity discharge lights along with that. These lights are more efficient plus good for flowering plants. There is also less guess labor when it comes from lighting distance to the crop. With that being said, HID bulbs get entirely hot plus the heat can burn the plants easily. What I use is LED grow lights. These are those purple, psychedelic lights that you notice. My marijuana cultivation facility is big, with high ceilings. This makes it great for my LED lights, then i don’t have to worry about the younger plants getting too warm. Just in case though, I do have an exhaust fan to vent out the heat. There is a small amount of guess labor on how hot the bulb gets. They do have a cooling function built into the bulb that pushes heat upwards… So I am pretty set there. I do think with LED lights you get a more consistent bud. I am entirely cheerful with my growing results. To each her own however.