MrStinkyanswered grow question 3 years ago If you start photoperiod or an auto at 12/12 they wont get very big - the auto wont reach potential as it blooms based on life cycle & not light schedules, and the photo wont get very big as you wouldnt be giving it a true veg cycle.
Best to start both on 18/6 - keep this constant until the end for autos and change to 12/12 to trigger your photos to bloom.