Re: T-8 lighting constr., part II
> From: james at home_xo.com (James F. Redfern)
> Date: Wed, 19 Feb 1997 22:59:24 -0800
> A bulb that is mirrored on half the surface is going to produce more
> light out the non-mirrored side than if it wasn't mirrored. Half the
> lumens do not disappear (nor just convert to heat).
Maybe, maybe not.
From a posting of mine long ago:
| I've collected more light data that should be of interest to folks
| plannng on buying new flourescent bulbs.
| We had a discussion some time ago about the possible effectiveness of
| bulbs with built-in reflectors. I had a chance to directly compare
| the same bulb with and without a built-in ("built-on" in this case :-)
| We have a month-old Coralife Trichromatic bulb with their version of a
| reflector (a piece of silver tape attached to the outside). We just
| got two Trichromatics without reflectors. I assume the bulbs
| themselves are the same and Coralife adds the tape and charges $3
| extra. Before installing them, we set them up in a spare shoplight to
| see what the differences might be. We also compared them to a 1 year
| old PennPlax Ultra Trilux.
| For the first test, a bulb was put in the Sears magnetic ballast
| shoplight with a Triton bulb in the other half. Both the Triton AND
| the reflector were covered with a black cloth to eliminate any
| external reflections and light. Two lux measurements were made. The
| first was done 3" from the bulb with the meter supported by a piece of
| 2 1/2" dia. PVC pipe. This is like a "spot" measurement and should
| show the intensity coming from the surface of the bulb, i.e., like
| from a single spot not including integration over the length. The
| second test was done 12" from the bulb and should be indicative of the
| light reaching the middle layers of the water, including the light
| summation from the whole bulb (more light at the middle than the
| ends). All values are in Lux (lumens per square meter).
| 3" 12"
| Trichromatic with reflector 5400 1060
| Trichromatic without reflector #1 5300 1100
| Trichromatic without reflector #2 5400 1160
| Ultra Trilux 7300 1480
| These results indicate that the Coralife concept of a reflector
| (silver tape on the outside of the tube) doesn't do anything for bulb
| intensity. It also shows that the Trilux is much brighter than the
| Coralife bulbs. They both appear to be the same color. Coralife
| claims a "6500K" color temperature; I measured 6150K to 6750K for
| the TriLux bulbs in a previous test.
| For the second test, just the Triton bulb was covered by the black
| cloth. This allowed the shoplight reflector (white paint or a white
| coating) to work sort of normally. Since the other bulb was covered,
| a little under half of the reflector was "out of service". I would
| expect higher measured values with a complete reflector, except in the
| case of the bulb with a built-on reflector. (The first measurements
| are in parenthesis for comparison).
| 3" 12"
| Trichromatic with reflector 5600 (5400) 1400 (1060)
| Trichromatic without reflector #1 7900 (5300) 1900 (1100)
| Trichromatic without reflector #2 7500 (5400) 1820 (1160)
| Ultra Trilux 10800 (7300) 2820 (1480)
| As I expected, the bulb with a built-on reflector did poorly here,
| since the bulb's reflector prevented most of the light from getting to
| the fixture reflector (the bulb refector covered 1/2 the bulb; some
| "side light" did get to the fixture reflector increasing the overall
| intensity a little).
| Bottom line: the Coralife "reflector" does nothing for bulb intensity
| and actually cuts the available light if used in a fixture with a
| reflector. I see no reason whatsoever for paying extra for a bulb
| with a built-on reflector. I see no reason to get the Coralife bulb
| instead of the Trilux, except perhaps for availability.
| Some time ago, using a different setup, I measured a Rainbow Lifeguard
| "BioLume" bulb with a built-IN reflector and was also unimpressed.
| The Biolume measured 4600 Lux and a group of TriLux bulbs measured
| 6700 to 7800 Lux (old to new bulbs).