new to autos just need some info on light distances??

Hello,
Im currently going to be getting some auto blue cheese and auto lemon haze ultra and i just ordered a 400 watt apollo frow light mh and hps and i was wondering, with autos should i start out with and keep with the hps or use mh in veg until i see white pistils then switch over to hps? Also with a 400 watt am i correct in saying i need to keep it at one foot or 12 inches away from plants at all times with autos??
Thanks guys!

seedlings i try to keep them around 2' away 12-18" after they are up and have real leaves...... the plant will preflower but its just showing sex it will continue to veg until it actually starts getting pom-pom like flowers/ the buds ball up and vertical stretch stops , thats when i consider the plant to be in flower

when in doubt on light distance use the back of your hand at canopy level .......

Ok cool thanks tekdc911, on another note i have some romulen bag seed going for my.second run while.im waiting on seeds and just using cfls which i used last tine but now im having weird issues with the leaves and im not sure if this is an actuall problem to be concerned with, ive risen and lowered the lights and it hasnt effected the plant at all with the leaves im running 2.5 teaspoon grow big and 2 tablespoon big bloom