HPS Bulbs

This is a general question (not sure I have EVER heard it asked though)
Why are some HPS bulbs elongated and tubular and others are short and round?

My first thought was the varying wattages, but then I've seen 400W in both styles.
Can anyone shed some light on this?





Shack

I think some are only compatable in certain ballasts. Not sure tho...

Long ones should be High Pressure sodium

Bulbus Ones - should be Metal Halide - they put and extra bulb on them to contain chemicals should they blow up.

Peace -

golddog said:

Long ones should be High Pressure sodium

Bulbus Ones - should be Metal Halide - they put and extra bulb on them to contain chemicals should they blow up.

Peace -

Click to expand...

explain this...





Shack

Not sure Shack,

But... most of them follow the pattern I described.

I know they put the extra glass on Metal Halide due to safety concerns.

.

It's a 150W bulb, they're wider and shorter than higher watt bulbs. Check out Ceramalux' 250W for comparisson. Ceramic bulb with an HPS spectrum. The scale ratio is not the same but you can see the shape difference.





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because some lighting nerd with a big calculator, a crazy computer and enormous access to an insane laboratory determined that the arc length of the spectrum is most efficient when compared to the highly volatile gasses that are contained inside the bulb.


in other words, I have no idea

i just thought it was for varying applications. the arc looks the same length in the pictures i've seen, with a 400 elongated next to a 400 "rounded" HPS

i was wondering if efficiency or anything like that could be affected.

probably not a big deal whatsoever.


Shack

different reflectors hold different bulbs and also different shape different spectrum