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Lighting
>
>Date: Fri, 29 Oct 1999 19:50:41 -0500 (CDT)
>From: Ivanstein at webtv_net (Ivan Trail)
>Subject: Lighting
>
>It was mentioned that a t-5 bulb puts out more than a t-12. Why is
>that? I had thought that a larger bulb would have more phosforescent
>(spelling?) material in it which would produce more light. I am
>interested in being corrected. Thanks.
>
>------------------------------
>
>Date: Fri, 29 Oct 1999 23:00:57 -0400
>From: "wayne jones" <waj at mnsi_net>
>Subject: Lighting
>
>>It was mentioned that a t-5 bulb puts
>out more than a t-12. Why is
>>that? I had thought that a larger bulb
>would have more phosforescent
>>(spelling?) material in it which would
>produce more light. I am
>>interested in being corrected. Thanks.
>
>T5 normal output lamps put out less
>light than a normal output T12 but most
>T5 lamps are high output lamps and will
>put out more light than the same length
>normal output T12. The phosphors in the
>T5 are also somewhat different than a
>regular T12 lamps. T5's always seem to
>employ rare earth phosphors which I
>presume are relatively expensive but not
>so much is required in such a small
>diameter lamp. In Europe linear T5's 1
>1/2 meters long have been available for
>a number of years and the HO version
>puts out a whopping 8000 lumens. The HO
>T5's unlike VHO T12's have long lamp
>lives and are quite efficient; somewhere
>around 80 lumens per watt.
>
>Wayne Jones
>
There are lot of factors involved into T8/T5 lamps. They run with higher
wall load (="current density over lamp surface"). That increases
efficiency. They mostly run with electronic ballast (ballast factor 1.0 -
1.1, comparing to 0.8 - 0.9 for conventional ballast. ballast factor shows
how many lumens you can get using that ballast comparing to nomial
"laboratory" ballast). High-frequency ballast also increase lumen output.
In general T5/t8 have better efficiency than T12
Model Philips TL80 lamps produce about 95 lumen per watt (comparing to
Coolwhite 75 LPW), their silhuette lamps have efficacy of 105 LPW. Silvania
makes similar lamps. You can also check European catalog at
www.philipslighting.com and www.osram.com. They make much better lamps for
Europe where people care about energy cost and efficiency.
CCT (corellated color temperature) is important. Coolwhite lamps have
largest LPW. Not because they produce more light. Just because lumens are
corellated with human eye and CW lamp has the advantage
Also, CRI (color rendering index) is very important factor when we talk
about lamp efficiency. Lamp with higher CRI has wider spectrum and this
reduce efficiency. FOr example, the most efficient light is a green laser -
about 700 LPW. (1 w = 683 lm at 555 nm wavelength)
And the most important factor why T5/T8 are better is that their brightness
is much higher. even if T8 produce same amount of lumens as T12 its
brightness would be 1.5 times higher, T5 - 2.5 times higher. And efficiency
of reflector is higher when brightness is larger.
Mike, who design weird optics around weird lamps