A led light bulb with a form factor of an incandescent light bulb. It has 12 leds and an E27 type screw fitting. This light bulb is from Technea Duurzaam, and for sale at De Energie Bespaarshop. It gives a very bright blueish light.

See this overview for a comparison with other lightbulbs.

Summary measurement results

parameter	meas. result	remark
Color temperature	8500 K	Very bright white
Luminous intensity Iv	8 Cd	The brightness is comparable with 8 candles.
Beam angle	120 deg	A wide beam.
Power P	0.9 W
Power Factor	0.17	For every 1 kWh net power consumed, there has been 5.8 kVAhr for reactive power.
Luminous flux	31 lm
Luminous efficacy	34 lm/W
CRI_Ra	81	Color Rendering Index.
Coordinates chromaticity diagram	x=0.288 and y=0.308
Fitting	E27
Diameter	70 mm	Measured at the widest part of the lightbulb.
Length	122 mm
General remarks		The ambient temperature during the whole set of measurements was 29-30 deg C. Warm up effect: hardly present (there is little effect, due to the little power that is consumed) Voltage dependency: present. FOr all raw measurement data follow this link (gogreen_08w_led_whiteglobe_e27.zip).

E_v at 1 meter distance, or also I_v

Herewith the plot of the average Luminous Intensity (I_v) dependent from the inclination angle with the lamp. Average here means that all Luminous Intensities measured with different turn angles but the same inclination angle, are averaged.

The radiation pattern of the lamp.

This radiation pattern shows a wide beam.

The luminous intensity dependent from the inclination angle, now with all turn angle measurements included.

The luminous intensity I_v is decreasing slowly, to get to its 50 % value at 60 degrees inclination angle. The beam angle of the light from this lightbulb is then 120 degrees.

The plot at the top of this paragraph shows the averaged luminous intensity values per inclination angle, which is used to compute the total luminous flux.

Luminous flux

With the luminous intensity data as a function of the inclination angle, it is possible to compute the luminous flux.

The result of such computation for this lamp is a luminous flux of 31 lm.

Luminous Efficacy

The luminous flux being 31 lm, and the power of the lightbulb being 0.9 W, yields a luminous efficacy of 31 / 0.9 [lm/W] = 34 lm/W.

A power factor of 0.17 means that for every 1 kWh net power consumed, a reactive component of 5.8 kVAr was needed.

Light bulb voltage	230 V
Light bulb current	23 mA
Power P	5.8 W
Apparent power S	5.2 VA
Power factor	0.17

Color Temperature and Spectral Power Distribution

The spectral power distribution of this lamp.

The measured color temperature is about 8500 K, and the light is very very bright, and blueish.

Chromaticity Diagram

The chromaticity space and the position of the lamp’s color coordinates in it.

The light coming from this lamp is close to the Planckian Locus (the black path in the graph).

Its coordinates are x=0.288 and y=0.308.

Color Rendering Index (CRI) or also Ra

Herewith the image showing the CRI as well as how well different colors are represented. The higher the number, the better the resemblance with the color when a black body radiator would have been used (the sun, or an incandescent lamp).

Each color has an index Rx, and the first 8 indexes (R1 .. R8) are averaged to compute the Ra which is equivalent to the CRI.

CRI of the light of this lightbulb.

The value of 81 is higher than 80 which is considered a minimum value for indoor usage. Since this lightbulb’s color temperature is higher than 5000 K, it is compared with the light of the sun or outdoor sky. When comparing, this light bulb renders the different test colors well enough. The light is so bright that it is blueish, which is not the type of light that is used for general reading.

Note: the chromaticity difference is 0.0027 which is lower than 0.0054, which means that the calculated CRI result is meaningful. This is because the chromaticity value of this lamp is relatively close to the Planckian Locus.

Voltage dependency

The dependency of a number of lamp parameters on the lamp voltage is determined. For this, the lamp voltage has been varied and its effect on the following lamp parameters measured: illuminance E_v [lx], color temperature CT or correlated color temperature CCT [K], the lamppower P [W] and the luminous efficacy [lm/W].

Lamp voltage dependencies of certain light bulb parameters, where the value at 230 V is taken as 100 %.

There is a dependency from the applied voltage. And the dependency there is, is also linear with applied lamp voltage. It indicates that the used power converter inside the lamp behaves stable.

To check whether this dependency can lead to visible changes in illuminance for possible grid voltage changes, just check what variations occur when the lamp voltage varies around 230 V + and – 5 V. Then the illuminance varies < 20 % and will not be visible or noticeable.

Warm up effects

After switch on of a cold lamp, the effect of heating up of the lamp is measured on illuminance E_v [lx], color temperature CT or correlated color temperature CCT [K], the lamppower P [W] and the luminous efficacy [lm/W].

Effect of warming up on different light bulb parameters.

There is little effect of the warming up on the lamp parameters. After half an hour burning the temperature of the light bulb is stable, and the illuminance is about the same as at switch on.