75W is good, and yes there is a point of regres, but it is still a questionabl topic. Remember some serious growers are dropping a 1K light on one plant for tramendous results. Now if they put a 600W on the same plant who is to say that they wouldn't have the same or better results. But for a 4x4 a 1K is perfect in my opinion.
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BlueBear Reviewed by BlueBear on . 115 watts per square foot I plan on using around 115 - 120 watts per square foot during bloom in a room 4x4 or 4x6. Is this way overkill for very high quality mary jane? Rating: 5