FLOWERING: MH vs. HPS YEILD Q'S

With all things the same, roughly how much more yeild can you expect using HPS over MH? Im kinda in a situation where Im not able to use my HPS for flowering my current crop so this batch is going all the way through under MH. How much less of a yeild could I be looking at?

Come on people I figured this was an easy question to answer for those with experience with both types of bulbs. I've never flowered with MH before so Im curious if my yeilds will be much less than using my HPS bulb? Theres gotta be some rule of thumb for % reduction or something?

How many watts?

not sure how much less you'll get by using a mh, but I know it will be better than cfl...I'm in the same boat, I am vegging under flo light and am going to have to flower with a 400 watt m.h......not ideal but will work

Im using 600w MH for veg and Im going to have to use the same light for flowering, instead of the usual 600w HPS.

guessing the difference in yield is almost impossible. plant size, pot size, enviorment, nutrients given all determine your original yield along with light of course. i would say dont worry about it unless you have plans on buying the hps if your yield would be effected largely. I would guess 15% less just because of the amount of lumens from mh to hps also spectrums. this is just a guess i really dont know

Thank KAOSOWNER for the input, a % less is really the answer Im looking for. And with all things the same, pot size, plant size, nute, etc. everything, the only variable changing is the light used for flowering, both cases being vegged under MH.