[smilez]

Does anyone see a problem using a 400w mh conversion bulb on a 600w hps digital balast?

Another question I have is do people ever continually shorten the light period during flower to mimic the suns gradual shorter days?

[D.I.Y]

Yer your waking 600w through a bulb only rated to 400w.dont fuck about with electrics yuo dont want a fire that would really piss on your cornflakes.go get yourself a new bulb

[Robert]

You'll burn your bulb out with a quickness.
If you turn your light cycle back slowly, your plants will be more likely to stretch, and will take longer to finish.

[theherbalizor]

Ballast and Bulb must be matched. PERIOD!

It can be useful on some sativas to start at 16/8 and slowly work down to 10/14 lights on / off.

But only on extremes that wont ripen otherwise, or will take 20+ weeks.

[The Kind Man]

I agree, I wouldn’t do that. You might burn your place down if it sparks and you are not there to put it out. The answer to your second question is I wouldn’t do that. You have to find an equilibrium so it will still flower but not revert back to vegetative state. More light = more photosynthesis = bigger, healthy and happier plants = better final result
|The Kind Man|
|Scientia Ipsum Est Vox|

[drpressure600]

the cores in a 600w ballast are built to control the power running to the electrons inside a 600w bulb, the 400w wouldn't stand a chance, dangerous messing with power like that bro . .

[arpege]

As everyone has stated.. Dont Do it!