ConstantColor CMH Elliptical Diffuse

Product information

Ceramic Metal Halide Lamps
70W and 100W

ConstantColor CMH™ lamps combine the HPS technology (providing stability, efficiency & uniformity) and the Metal Halide Technology (providing bright white quality light) to produce highly efficient light sources with good colour rendering and consistent colour performance through life. This is achieved by using the ceramic arc tube material from the Lucalox™ lamp, which minimises the chemical changes inside the lamp through life. When combined with the halide doses used in Arcstream™ Metal Halide lamps then the quality and stability of the dose maintains the colour consistency. Hence the name ConstantColor CMH™ .

Application areas

  • Architectural floodlighting
  • Street lighting
  • City beautification
  • Indoor lighting
  • Stage/studio


  • Easy retrofit for High Pressure Sodium lamps
  • No ballast thermal protection required
  • Excellent colour rendition
  • Consistent colour over life
  • Colour uniformity lamp to lamp
  • 15,000 hours life
  • Up to 24% higher efficacy than quartz metal halide
  • UV control

Elliptical format

Conventional lamp shape with a screw-type base enables existing luminaire designs to use ConstantColor CMH™ lamps with little or no modification to the optical system. Coated and clear versions enable close matching to the lamp types previously used.

Specification summary

Rated Wattage [w] 73 73 73 73
100 Hours Initial Lumens [lm]  6,300 6,000 6,300 6,000
Rated Lumens [lm] - - 6,300 6,000
Typical Voltage Change with Burning Position – Vertical to Horizontal [V] 5 5 5 5
Correlated Colour Temperature [K] 3,100 3,000 3,100 3,000
Chromaticity X 0.435 0.438 0.435 0.438
Chromaticity Y 0.414 0.408 0.414 0.408
Colour Rendering Index [Ra] 80 82 80 82
Luminous Efficacy [lm/W]  85 81 86 82
Rated Lamp Efficacy [lm/W] - - 86 82
Bulb Finish Clear Diffuse Clear Diffuse
Arc Gap [mm] 7 7 7 7
Bulb Designation BD17 BD17 BD17 BD17
Base E27 E27 E27 E27
Mercury Content [mg] 5 5 5 5
Ambient Temperature [°C] 25 25 25 25
Starting Characteristics <10
Time to Start (at 25°C) [s] <30
Time to Start – Cold box test at -30°C [s] 4
Warm-up Time (for 90% lumens) [min.] 2.7
Pulse Peak Voltage – Min. [kV] 5
Pulse Peak Voltage – Max. [kV] 2
Pulse Width @ 90%of Min Pulse Peak Voltage [ms]  Min. 1 above specified pulse in each half period
Hot Restart Time [min.]  15
Through Life Performance
B5 [h] 8,500
B10 [h] 10,000
Average Rated Life [h] 15,000



Wattage [W] 70 W 100 W
Maximum Overall Length (MOL) [mm] 133±4 133±4
Nominal Bulb Diameter (Dia.) [mm] 55 55
Light Center Length (LCL) [mm] 86±3 86±3
Burner width [mm] 8.8 8.8
Burner height [mm]  13.8 16.8


In certain cases, dimming may be acceptable, subject to further testing. Contact your GE representative for more information. Large changes in lamp power alter the thermal characteristics of the lamp resulting in lamp colour shift and possible reduction in lamp survival.


When ConstantColor™ CMH lamps are operated from a conventional magnetic ballast there will be 50Hz line frequency light output flicker typically of 1.5%, in common with all other discharge lamps. Noticeably lower flicker levels occur when lamps are operated horizontally.

Flicker levels of 1.5% do not normally cause concern to the end user, but use of electronic control gear should be considered where visual comfort and performance is critical. Suitable electronic ballasts for ConstantColor™ CMH typically provide square wave operation in the range 70-400Hz, eliminating perceptible flicker.

End-of-life Conditions

The principal end-of-life failure mechanism for CMH lamps is arc tube leakage into the outer jacket. High operating temperature inside the arc tube causes metal halide dose material to gradually corrode through the ceramic arc tube wall, eventually resulting at normal end-of-life in leakage of the filling gas and dose. Arc tube leakage into the outer jacket can be observed by a sudden and significant lumen drop and a perceptible color change (usually towards green). 

The above situation is often accompanied by the so-called rectification phenomena. This occurs where a discharge is established between two mount-frame parts of different material and/or mass, causing asymmetry in the electrical characteristic of the resulting discharge current. Rectification can lead to overheating of the ballast, therefore conventional magnetic ballasts must conform to requirements of the IEC61167 lamp standard by incorporating protection to maintain safety and prevent damage.

End-of-life cycling

A condition can exist at end-of-life whereby lamp voltage rises to a value exceeding the voltage supplied by the control gear. In such a case the lamp extinguishes and on cooling restarts when the required ignition voltage falls to the actual pulse voltage provided by the ignitor. During subsequent warm-up the lamp voltage will again increase, causing extinction. This condition is known as end-of-life cycling. Normally cycling is an indication that lamp end-of-life has been reached, but it can also occur when lamps are operated above their recommended temperature. Lamp voltage at 100 hours life should not increase by more than 5V when operating in the luminaire, when compared to the same lamp operating in free-air. A good luminaire design will limit lamp voltage rise to 3V.

It is good practice to replace lamps that have reached end-of-life as soon as possible after failure, to minimise electrical and thermal stress on ignitor internal components. The use of a ‘timed' or ‘cut-out' ignitor is not a specific requirement for ConstantColor™ CMH lamps, but is worth considering as a good optional safety feature which also prolongs the life of ignitor internal components, lamp holder contact surfaces and fixture wiring.

The operating period of a timed/cut-out ignitor must be adequate to allow lamps to cool and restart. A period of 10 to 15 minutes continuous or intermittent operation is recommended before the ignitor automatically switches off. Timed/cut-out ignitors specifically offered for High-Pressure Sodium lamps, where the period of operation is less than 5 minutes, are not suitable for ConstantColor™ CMH lamps.

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