variable

I recently performed a lighting experiment with some Dianthus, slowly bringing up light intensity over a 20-minute period of time at the beginning of the 18-hour cycle and then decreasing the intensity slowly over another 20-minute period of time, just before the 6-hour night cycle. The results...

I have a 600w variable ballast. Can anyone enlighten me as to the point of these ? How do I use one correctly as I have one 600w bulb... Do I need to turn it down to the 400w setting towards the end of flowering to simulate the ending of summer transition to Autumn to try and replicate the...