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In a message dated 98-09-15 04:00:54 EDT, you write:

>  >The main disadvantage with mercury lamps is you get about a third more 
> light
>  >[photosynthetically  active radiation] out of a metal halide of the same
>  >wattage.
>  snip snip ..
>  yes but how are they compared to flourecents ... and another thing .. they
>  cost 1/3 of the price MH bulbs go for too ..and i THINK .. they produce
>  heat that MH bulbs .. is it true that they produce blue light .. ive never 
> seen
>  any of these in action .. just an idea id be willing to try .. seems more
>  hi-tech than the normal flourecents .. SEND FEEDBACK

Mercury vapor (MV) lamps are not as efficient as fluorescents (35 - 55
lumens/watt, where fluorescents can be as high as about 92).  I think they
maintain there light level better than MH, but I'm not sure.  One thing you'll
really have to watch out for though is the color rendering.  Uncoated MV only
have a CRI of 15, which is worse even than high pressure sodium lights (those
pinky-yellow street lights).  MV's are available in "Deluxe" coated bulbs, but
the CRI (color rendering index) is still only 50, which is a little worse than
the old "cool white" fluorescents (CRI 62).

MV's produce the same heat as the same wattage MH's, but you get less light
and poorer colors.  On the other hand, you don't have to change the lamps as
often. There are special MH lamps that can be used in MV fixtures, but they
are probably gonna be expensive.  Still, if you set up MV lights and don't
like them it might be a good way to convert to MH.

best regards,