Since the last set of reflector tests in 2004, I have received
five new reflectors for various metal halide lamps. This article
presents test results on the fixtures/reflectors available for
these lamps. The reflectors were tested using the same setup and
methodology as used for the tests on other reflectors, described
in [1]. The data is also presented in an identical manner with
plots for light dispersion for each reflector at distances of
6″, 9″ and 12″ from the center of the lamp. This
article continues in a similar vein as the previous reflector
articles and presents the data and analysis of the remaining
reflectors in my inventory.

Reflector Data and Analysis

The data plots for each reflector at the distances 6″,
9″, and 12″ are plotted as a surface graph, top view
graph, and a % distribution graph to illustrate the intensity and
spread at different points on the measuring grid. Table 2 below
shows the list of figures associated with each reflector.

One of the measures of a reflector performance could be its
ability to direct light into the aquarium. A reflector’s
total incident light upon a surface of a given area is
representative of the performance of a reflector. It is computed
by adding up all the measurements taken at the discrete points
within the region. It demonstrates how much light the reflector
is able to focus downward when compared to other reflectors with
similar operating conditions (same ballast and lamp). While it
can be argued that adding all the PPFD values is technically not
a valid measure as per the definition of PPFD (since PPFD is
defined as microEinstiens/m²/sec), it can be used to
provide a metric for reflector performance. Further summing over
the data points on a given area can easily be used to compute the
average, if so desired. Since the area under consideration is the
same for all reflectors, we can just as well use the sum of the
PPFD values distributed over this area (169 data points) instead
of an average as a performance metric.

Table 3 presents this data for the reflectors in this article.
Note that the initial PPFD values of the lamp/ballast combo used
to test the reflector influences this data. For example, the PFO
DE reflector used a 400W DE lamp on an HQI ballast with a PPFD
value of 229 where as the Sunlight Supply Lumenmax used an Ushio
400W lamp on a magnetic ballast with a PPFD of 120.

In addition to knowing how much light is incident on a given
area, we could also look at how much loss of light occurs on a
given area when moving the lamp and reflector higher. Table 4,
presents the % of light lost on a specified area as one moves the
lamp/reflector from 6″ to 12″ above the surface. A
higher % loss would indicate that the reflector is creating a
larger spread.

Conclusion

This article is the 5th (and possibly last) in this series and
presents the data and a brief analysis some of the new reflectors
I received in the past year.

Acknowledgements

We would like to thank several people whose help made this
study possible. They were kind enough to provide us with lamps,
reflectors and ballasts for testing: Patrick at PFO Lighting,
Andy at Icecap, Dave at Sunlight Supply.

References

1. Joshi, S. and Marks, Timothy. 2003. Analyzing Reflectors:
   Part I – Mogul Reflectors
   
   http://www.advancedaquarist.com/issues/mar2003/feature.htm