(((((((((((((((CFLs are still fluorescents, despite being physically smaller than the traditional long tubes. Fluoros make low intensity light; the intensity drops dramatically only a few inches away from the lamp tube. This is generally OK for slow-veg of small plants. However, good bud development requires the high-intensity light you only get from HID lighting.
CFLs as such are not revolutionary nor in any way 'the next big thing.' They DO have some good applications with clones and early vegging, though. Even the big 100-300W CFLs as used in Envirolites and other fixtures, while brighter (more intense) than their small grocery-store cousins, still produce low-intensity light. These big CFLs will do better with flowering than the small ones but simply can't produce the same results as even a small HPS. A 150W HPS will kick the pants off a 150W CFL in flowering due to the difference in luminous intensity.
One point that even long-experienced growers miss is that
lumens don't 'add.' Lumens are a measure of light intensity, which the human eye interprets as brightness. If you have a 1500 lumen CFL and you put another 1500 lumen CFL beside it, the total luminous output in the effective coverage area near your two CFLs is- wait for it- 1500 lumens. Just because you put one CFL next to another does not make either lamp any brighter or more intense.
Reduced: 64% of original size [ 800 x 601 ] - Click to view full image
For the above image, I set up two 20W CFLs in two fixtures, let them warm up for about 5 mins and measured the luminous output around them at a distance of 50mm. The
lux meter read around 63-65K lux from the sides of either CFL by itself. When the lux meter sensor is placed so that it is as close as practicable to within 50mm of both tubes, the meter still reads 63-65K lux.
Luminous intensity from multiple sources acts like voltages in parallel. If you put two 1.5V batteries in parallel, you get 1.5V. Same with luminous intensity. As said previously, if you put two 1500 lumen lamps next to one another, you have... 1500 lumens. Neither lamp gets any brighter just because they are next to one another. Luminous intensity is not a measure of the volume or number of photons being thrown at a given point but rather the energy pushing them, analogous to voltage in an electrical circuit.
Consequently, you can put all the 1500 lumen CFLs you want in a grow but the luminous intensity will remain at 1500 lumens. If you need more intensity, you need a more intense (brighter) light, not more low-intensity lights.))))))))))))))
Here is an article from a different website.