Newsgroups: sci.aquaria

I recently made some intensity and color temperature measurements on a
bunch of fluorescent and metal halide bulbs and would like to share
the data with you.

My goal was to determine the relative brightness of various bulbs (to
check out the claims of the vendors) and to get a feel for the color
temperature of the bulbs.  A secondary goal was to determine the
effects of age on both color temperature and brightness.

To measure intensity, I used a lux meter offered by Marine
Invertebrates, Inc.  This is advertised in FAMA and costs about $100.
I'm not sure about its absolute accuracy, but, being digital, its
resolution is quite good.  The instructions claim an accuracy of +/- 5
lux and it seems very repeatable.  I'm also not sure about how color
temperature affects its accuracy.  Its response curve peaks at about
600 nm, so there is probably some effect.

To measure color temperature, I rented a Minolta Color Meter II from a
photographic supply store in Denver.  It's primary use is to determine
the correction filters required to balance a specific film for a
specifc light source, but it also indicates color temperature in
degrees Kelvin.  I'm not sure of its absolute accuracy (and I did see
some strange results with metal halide lights), so take the numbers
with a grain of salt.  This is a neat instrument that sells for about
$700, so I feel that numbers aren't too far off for the fluorescent
bulbs.  Minolta also makes a different meter for "scientific and
industrial colorimetery", but it's not available for rental locally.

BTW, I tried to call the Minolta Customer Service Department to determine
the validity of my measurements, but the "representative was busy and
his voice-mail was full", so I couldn't leave a message.
 
This posting is the raw data I collected.  I have not as yet drawn any
conclusions aside from obvious things like Penn-Plax Ultra TriLux
bulbs are brighter than Triton bulbs and they have a color temperature
closer to sunlight (whether or not that is good, I'm not saying). 

Perhaps one of the net light experts could comment on the data.

--------
George

=====================================================================

Light Fixture Effects 
---------------------

To determine if the light fixture and ballast affected the temperature
and intensity, 2 new 40 W Cool White bulbs (2 for $2.49) were tested
in two fixtures.  The readings were taken 8" from the bulbs, centered
over the middle of the fixture.

An "electronic" shop light ($15.99 at Ace hardware) with a small coil/
capacitor ballast circuit produced 5000 K and 5500 Lux.  This is an
"energy saving" type fixture.  My experience indicates this type of
fixture is hard on bulbs such as Tritons and shortens their life.

As a side note, the October '92 Consumer Reports tested various types
of energy saving light bulbs including compact fluorescent bulbs with
electronic and magnetic ballasts.  They found that a large number of
the bulbs with an electronic ballast had premature failures.

A "standard" Sears shop light with a normal magnetic ballast produced
5300 K and 6650 Lux.  The same fixture with aluminum foil behind the
bulbs produced 5300 K and 7900 Lux.  Also with this setup, the color
temperature ranged from 5200 K to 5500 K when the distance from the
bulb varied from 3" to 24".

I also tried to check the lights in a Coralife metal halide and
fluorescent fixture to see if an "expensive" ballast and polished
reflector did anything, but the bulb spacing was very different giving
readings which could not be meaningfully compared to the first three.
 
Conclusions: 
1) Cheap electronic fixtures reduce your light intensity and bulb life.
2) Cheap reflective material can increase your light intensity.

Color Temperature (single bulbs)
--------------------------------

I had hoped to determine color temperature and aging effects of metal
halide bulbs, but the temperature meter responded very strangely to
most of the bulbs I tested, giving readings of 9000 K to 14000 K
depending on the distance from the bulb.  One older, 1000 W MH bulb
read 6200 K, but I don't have much faith in that number.  By the way,
an actinic bulb caused an "overrange" reading (above 40000K).

The local fish store allowed me to check some of the bulbs in the
store.  Most of the bulbs are about 1 year old.  I was surprised at
the temperature range of the 40 W Power-Glo bulbs; possibly caused by
differing age or fixture differences or just bad quality control - I
don't know.  I believe the higher K temperature indicates more blue,
which shows up some fish colors better.

20w Ultra TriLux     5200 K   new      (in a cheapie hood)
Phillips UltraLume   5800 K   6 months
Artic Brite          6000 K   1 year
Power-Glo            7200 K   
  "    "             7850 K   
  "    "             8700 K
  "    "             8700 K                      
  "    "             9350 K
  "    "             9800 K

A local lighting store has a light bulb comparison center with various
commercial bulbs.  The age of the bulbs was unknown.  Unfortunately,
the store was remodeling and some of the display was not working, so I
didn't get a chance to try a Chroma 75.

Warm White Delux     3460 K
Warm White           3630 K   
Regal White          3640 K   
Natural              3900 K
Spectra 35           3930 K
Spectra 30           3930 K
Chroma 50            4600 K   
Cool White           5000 K
Cool White           5150 K   
Daylight             7500 K

We have quite a few bulbs of various ages on hand.  Each was tested in
the Sears shop light.  The second bulb in the fixture was covered with
a piece of cardbard so it would not affect the readings.  The age of
the the bulb is indicated, if it was known.  All readings are 8" from
the bulb.

Agro Lite            3590 K
Wide Spectrum        3900 K
Advantage X          5300 K          5100 K in electronic fixture
Artic Brite          5850 K    new   5900 K in electronic fixture
  "    "             5700 K    
Ultra TriLux         6750 K    new
  "     "            6350 K          6050 K in electronic fixture
  "     "            6150 K
  "     "            6150 K
Triton               8150 K    new
  "                  8400 K    new
  "                  7550 K    300 hours
  "                  7550 K
  "                  7350 K    4800 hours


Color Temperature (combinations)
--------------------------------

Combinations of bulbs in use on our various plnated aquariums were 
tested.  The average age of the bulbs is about 6 months. 

1 Power-Glo, 
1 Ultra TriLux       6550K   

1 Triton,            from 
1 GE Wide Spectrum,   6000 K   
1 Triton,              to 6300 K
1 Ultra TriLux          to 6500 K 

1 Ultra TriLux,      from 
1 Ultra Trilux,       6150 K 
1 Triton,              to 6050 K
1 Ultra Lume            to 5900 K

1 Artic Brite,
1 Ultra TriLux       6400 K


Intensity (single fluorescent bulbs)
------------------------------------

From the local fish store (meter was 4" from the bulbs except for the
metal halide bulb): 

1000 W Metal Halide, 12" from fixture   69,000 Lux
2 Power-Glo bulbs,                      11,000 Lux
1 Power-Glo, 1 Ultra TriLux              8,200 Lux
1 Power-Glo, bad fixture                 2,400 Lux

From the local lighting store (meter was 4" from the bulbs):

Regal White          3300 Lux 
Chroma 50            3500 Lux 
Warm White           4600 Lux 
Cool White           5000 Lux

Our bulb stock (meter was 8" - twice as far - from the bulb):

Wide Spectrum        2400 Lux
Artic Brite          3750 Lux  new   2780 Lux in electronic fixture
  "    "             3200 Lux  
Advantage X          4200 Lux        3370 Lux in electronic fixture
Triton               3890 Lux  new
  "                  3820 Lux  new
  "                  3730 Lux  300 hours
  "                  3610 Lux
  "                  3300 Lux  4800 hours
Ultra TriLux         5000 Lux  new
  "     "            4720 Lux        3520 Lux in electronic fixture
  "     "            4580 Lux
  "     "            4480 Lux


Intensity (single 5500 K metal halide bulbs)
--------------------------------------------

We have had our dual 175W metal halide fixture in use for over 1 year
and have tracked the intensity of 3 of the 5 bulbs in use over that
period.  The bulbs are on for 10 hours per day.

Directly below the bulb at the acrylic shield:

Bulb 1:  78,000        90 to 270 days
         72,000        320 days
         57,000        360 days

Bulb 2: 126,000        10 minutes
        110,000        4 hours
        102,000        2 days
         94,500        4 days
         90,000        13 days
         90,000        21 days
         86,500        62 days
         82,000        110 days
         72,000        285 days
         60,000        315 days

At the water surface, 13" from the bulb:

Bulb 2:   9,900 Lux    1 year old; replaced at this point

Bulb 3:  19,900 Lux    after 2 hours
         17,600        1 day (12 hours)
         17,100        2 days (22 hours)
         16,900        3 days
         16,400        4 days
         15,700        6 days
         15,700       16 days

I was very surprised at the rapid initial drop off of intensity from
the MH bulbs; I had expected a linear drop for most of the lifetime. 
The data indicates that MH bulbs should be changed once a year if
you have intensity sensitive applications.