In addition to the four rare-earth phos-
phors, the RE-90 3000 K lamp has filters to
reduce the quantity of blue light caused by
mercury radiation, balancing the color. Light
output of RE-90 lamps is reduced by one-
third, but this is often imperceptible because
of the vivid and accurate colors, which
improve contrast and portray tones that are
otherwise grayed with lamps of lower CRIs.
T5 (^58 -in-diameter) fluorescent lamps
are only manufactured in metric lengths and
with a miniature bipin base, and are
designed to operate solely on electronic bal-
lasts. Their smaller diameter provides even
better optical control than T8 lamps. Addi-
tionally, T5 lamps produce optimum light
output at an ambient temperature of 95ºF
(35ºC) rather than the more typical 77ºF
(25ºC) of other fluorescent lamps, allowing
for the design of more compact luminaires
that do not require added size to dissipate
heat.
T5 lamps are also available in high-
output versions providing almost twice the
light output per length as their standard T5
counterparts. At the present time, all T5
lamps are available only with RE-80 phos-
phors.
Variations
Energy-savingor reduced-wattage lamps are
interchangeable with standard lamps; they
consume less power and deliver less light.
Input wattage is reduced by 12 to 15 per-
cent; lumen output is reduced by 10 to 20
percent. Energy-saving lamps are more sen-
sitive to low temperatures than standard
lamps: minimum starting temperature is
60°F, as opposed to 50°F for standard
lamps.
T8 and T12U-bentfluorescent lamps
are regular 4-ft lamps bent into a “U” shape.
This configuration allows two or three 4-ft
lamps to be used in a 2-ft-square luminaire,
with the further advantage of wiring and
lampholders being conveniently located at
one end of the luminaire.
T8 U-bent lamps are available in 1^58 -in
and 6-in leg spacing, with the 6-in leg spac-
ing more common. T12 U-bent lamps are
available in 3^58 -in and 6-in leg spacing, with
the 6-in leg spacing again more common.
Circular “circline” lamps are T9 (1^18 -in-
diameter) tubes bent in a circle with the two
ends adjacent to each other and a single,
four-pin connector base. They are available
in 6½-, 8¼-, 12-, and 16-in outside diame-
ters. Circline lamps are of the rapid-start
design but operate equally well on preheat or
trigger-start ballasts.
Circular T5 lamps are also available, in
9- and 12-in outside diameters. These lamps
have a single base with a two-pin connector.
High-output(HO) T12 rapid-start lamps
operate at 800 milliamperes (mA), com-
pared with 425 mA for most standard rapid-
start lamps. They produce about 45 percent
more light than slimline lamps of corre-
sponding physical size as a result of drawing
considerably more current than the standard
lamps.
High-output lamps are identified by
lamp length, bulb diameter, color, and the
lettersHO. For example, F96T12/RE830/HO
is an 8-ft, 1½-in-diameter, rare-earth, 3000
K, high-output lamp. HO lamps are available
in lengths from 18 to 96 in, with a variety of
phosphors and color temperatures, and in
reduced-wattage, energy-saving versions.
Very-high output (VHO)T12 lamps also
operate on the rapid-start principle at 1500
mA. They produce up to twice as much light
as standard lamps of equal length, while
using approximately three times more power.
These are the most powerful fluorescent
lamps available.
Reflectorandaperturelamps contain an
internal reflector on part of the inner surface
of the tube to provide built-in directional light
control. The un-reflectorized portion of theDISCHARGE LAMPS