Its complex, if you want to maximize yield.....
Autos tend to be a squat plant by their make up. To get an auto to yield its best to have a taller plant structure, hit them with too much light early on and they remain too short and little light gets though to where its needed.
I find the easiest way to do this is to stretch the plants during the rapid growth stage at 3 to 5 weeks. To do this raise the lights and run them at 18/6. When you have the stature you can then put them up to 20/4 and lower the lights and give them all you have got. If you have 2 lighting circuits then you can switch one off and leave the other on constantly.
I run on an 18/6 schedule with everything running then switch off the main lights and run LED only during the 6 hours, so really its 24/0 but with reduced lighting for 6 hours, I hope that makes sense.
This means you can encourage the autos to grow a decent size and give room and space for great bud development, then when you have things right you can give them everything they need to fill out.
The plant in these pictures is a lowryder 2, which was grown following this schedule in one of my CF/LED boxes.
Peace and love.......