E2S warning signals - guide to specifying visual signals
Technical Report - Intensity Distribution and Light Output Ratio
1. 1 | P a g e
Year 2 Block 5 By Martin Jesson
Intensity Distribution
and
Light Output Ratio (LOR)
Abstract
Replacement. Equivalent. Energy saving – these are key terms used in the marketing and branding of
lamps. The fallacy is that while yes, a given lamp may use less watts and have the same lamp holder,
the lamp is only one piece in a two piece puzzle. Overall efficiency is determined by light output of a
luminaire, not solely by the type of lamp used. This Report will conduct a basic photometric test of 4
common lamps and compare their light out ratio. Is a CFL more ‘efficient’ than a 100 GLS?
2. 2 | P a g e
Introduction
Light Output Ratio
Light Output Ratio (LOR) is essentially the efficiency of a luminaire expressed as a percentage. It’s a
measure of how well the luminaire distributes the lumens of its light source. This being derived from
the sum of the total lumens of the lamp and the actual measured lumens distributed out of the
fitting. These two factors can be further surmised to:
• Constant – If maintained, the luminaire will have a permanent level of efficiency as dictated
by its design, materials used and thermal dynamics.
• Variable – The lamp, any number of different lamps could be substituted into the luminaire
which would make its published LOR void. If published photometric data is to be used then it
is imperative the listed lamp is also used.
Intensity Distribution
Intensity Distribution is how a given combination of luminaire and lamp ‘delivers’ light and is often
referred to as measurements of ‘Delivered Lumens’. This information is typically conveyed in a
polar curve diagram which shows the intensity of the light at any given angle. The sum of intensity
values outlined in the polar diagram are used to determine the LOR of the luminaire.
The lamp can prove an obstruction to light output.
If the lamp ‘Centre’ dimension is changed the reflector
will not be optimized .
This luminaire is designed to take an 18W PL lamp. Note
how the CFL is positioned horizontally.
3. 3 | P a g e
We can see from this graphic that 100% of the distributed light is thrown downward. Therefore we
can determine LOR =DLOR (D =Down). Luminaires can be designed to have an indirect light
component in which a percentage of light is cast upwards. LOR of such designation is therefore split
to show an DLOR & ULOR.
This picture is a graphic illustration of how the polar curve
is derived for luminous flux. You can see here how the
light is almost at 80deg to the vertical.
Note how this distribution is only on one axis.
Photometric testing is conducted over many axis in order
to get comprehensive information.
This Figure is a Photometric illustration of the
Dot122 as published by Dot and imported into
AGi32 Design software.
Note the many planes that are used to give a
comprehensive 360deg representation of the
distribution of the luminaire.
This published photometric data represents a
symmetrical circular distribution pattern
This published photometric data lists a 100W GLS as the lamp and
represents a symmetrical circular distribution pattern with an LOR
of 65.2%. Or in other words, the luminaire will deliver 65.2% of the
lumens of the 100W GLS. This luminaire is designed to incorporate
a 100W GLS lamp and its LOR is only 65.2%. This would not seem
very efficient design. The real question is, will other technologies be
more efficient? Does an equal lamp lumen output and lower
wattage translate into energy efficient? The following experiment
will compare 4 typical lamps types LOR to find the highest achiever.
4. 4 | P a g e
Method
Apparatus:
• Dot 122 Downlight luminaire
• Lamps
o Philips Tornado 20W CFL
o Philips 100W Softone
o Philips 70W Halogen
o Sylvania 100W (clear)
• Chroma Electricity Supply – Set to 240v ~ 50hz
• Illuminance meter – Hagner ECI
• Turntable with measurable units of degrees of rotation
• Results table
Procedure:
1) The Equipment was set up as per figure 1.
2) The Chroma Electricity supply was set to 230v AC 50Hz
3) Inserted CFL lamp into downlight and was turned on 1hr prior to experiment to allow for
suitable run in/warm up time.
4) Turn on Illuminance meter and ensure aiming is at Zero degrees.
5) Ensure downlight at zero degrees
6) Take Illuminance measurement and record in results table.
7) Downlight was then rotated left to specified angle outlined in results table and measurement
recorded
8) Repeat step 5 until at 90 degrees.
9) Repeat step 6 rotating in direction = Right
10) Repeat steps 5-9 for all 3 remaining lamps.
Figure 1
8. 8 | P a g e
Discussion
Limitations:
On the whole, the data does not replicate that published by Dot. We must acknowledge the
limitations of the experiment in order to explain this. Firstly, we are only measuring intensity of one
plane. This presents a problem because if you look closely at our lamps filaments, they are not
symmetrical. The Filament is long and skinny, essentially the end of the filament is closer to the
reflector then the middle, which creates two different points of distribution which cannot be equal.
This is further identifiable by analysing the ‘left’ and ‘right’ illuminance readings, we can see they
differ. Lamp positioning within the luminaire is also an inaccuracy which must be taken heed of. This
luminaire is orientated on a horizontal plane which may cause the lamp to be positioned off centre.
The lamps were not burnt into their 100hr threshold, and they are subject to manufacturing
tolerances, so the rated flux may be at the extreme of the ± parameters. The experiment was not
conducted at 25°C controlled temperature.
Analysis of Results:
If we look at the below polar curve published by Nimbus lighting for the DOT122 downlight as used
in this experiment. We can clearly ascertain the intensity at a given angle. It can be determined that
maximum intensity values will be at angles 20deg from the vertical. We can also determine the
beam angle of 90deg.
Predominantly downlights designed for CFL lamps incorporate ‘PL’ lamps which are compact tubes
arranged in a longer format which better suits fluorescent technology. Refer ‘CFL Downlight’
diagram in the introduction. This luminaire has larger CFL lamps which are more efficient and uses
them horizontally in order to negate any potential for glare nuisance.
If we now look at the Philips 100W soft tone and the 70W Halogen. Both have rated output of
1200lm but the halogen consumes 30% power. For the Dot122 luminaire we can see that the
halogen doesn’t do as greater job distributing its lumens as the 100W with an LOR of 51% - 2% less
If we refer to the CFL Illuminance data we notice that the values are
markedly increased at the larger angles. For example at 50,60,70deg
the CFL has more than double the output of the other incandescent
lamps. This would translate to a wider beam angle then the published
data.
The Sylvania 100W GLS and the CFL have similar outputs of 1340 and
1350 respectively, yet the Sylvania had 8% less LOR. Reasons for this
is because physically the CFL is longer and wider which enables more
light to be distributed without the aid of the reflector. Essentially, the
in-efficiency of the reflector doesn’t feature as its not used. Whilst
the CFL may deliver more lumens, a glare issue may also present
itself.
9. 9 | P a g e
than the 100W. From this analysis it can be determined that the Halogen would be an energy
efficient option over the 100W Softone as although it has a 2% reduction in light output, it does have
30% energy saving.
Conclusion:
Despite its limitations, this experiment does highlight the variable nature of the output due to the
physical nature of the lamps. The small compact design of the Dot122 means the lamp poses a
hindrance to the light output which probably accounts for the relatively low LOR of all 4 lamps. By
measuring only one plane of distribution the asymmetrical characteristics of the lamps were
amplified. This was especially visible in the CFL which had a larger beam angle then the incandescent
samples. This can only be attributed to its larger size and would most likely have a greater potential
to present a glare of all the lamps tested. Which leads to a compromise of energy savings over
comfort which I believe is the greatest issue facing todays lighting designer. The balance of comfort
and cost.
10. 10 | P a g e
References
Illuminating Engineering Society of North America (1993) Lighting Handbook, 8th
Edition,
Warren G Julian (2011, February). Lighting: Basic Concepts, 6th
Edition,
http://archive.luxmagazine.co.uk/2011/07/all-led-downlights-are-100-efficient/
http://www.emmlight.com/producten/thorn-led-downlights/
http://www.pge.com/myhome/edusafety/workshopstraining/pec/tour/light5.shtml
http://www.dotdownlights.com/
