LEDITLIGHT – 18x smd led lamp G4

Posted by Marcel van der Steen in Led lights, Light measurements No Comments»

lil_gu53_18smdleds presents a led lamp with smd leds on a set of plates soldered together in a tube form. This light bulb emits warm white light.

This article shows the measurement results. Many parameters are also found in the Eulumdat file.

See this overview for a comparison with other light bulbs.

Summary measurement data

parameter meas. result remark
Color temperature 3151 K Warm white
Luminous intensity Iv 10 Cd Measured straight underneath the light bulb
Beam angle 306 deg 306º for all C-planes as this light bulb is symmetrical around its 1st axis.
Power P 2.2 W
Power Factor n.a. This light bulb was powered with a DC voltage resulting in no blind power so Power Factor is always 1.0
THD n.a. Total Harmonic Distortion
Luminous flux 147 Lm
Luminous efficacy 66 Lm/W
CRI_Ra 57 Color Rendering Index.
Coordinates chromaticity diagram x=0.4329 and y=0.4145
Fitting G4 This light bulb is tested with 12 V DC.
PAR-value 0.1 μMol/s/m2 The number of photons seen by an average plant when it is lit by the light of this light bulb. Value valid at 1 m distance from light bulb.
PAR-photon efficacy 0.5 μMol/s/We The toal emitted number of photons by this light, divided by its consumption in W. It indicates a kind of efficacy in generating photons.
S/P ratio 1.1 This factor indicates the amount of times more efficient the light of this light bulb is perceived under scotopic circumstances (ow environmental light level).
H x D external dimensions 23 x 19 mm External dimensions of the lamp (L = length, without the pins).
H x D luminous area 23 x 19 mm Dimensions of the luminous area (used in Eulumdat file). This is equal to the tube form of the the surfaces on which the leds are mounted.
General remarks The ambient temperature during the whole set of measurements was 23.5-25 deg C. The temperature of the lamp gets about 65 degrees hotter than ambient.
Warm up effect: during the warm up time the illuminance decreases with 23 % and the consumed power with 8 %.

Voltage dependency: the power consumption and illuminance do not vary significantly when the voltage is varied from 200 – 250 V.

Measurement report (PDF) .
form factor all around
Eulumdat file olino_eulumdat Right click on icon and save the file.

Overview table


The overview table is explained on the OliNo website. Please note that this overview table makes use of calculations, use this data with care as explained on the OliNo site. E (lux) values are not accurate, when within 5 x 23 mm ≈ 120 mm. Within this distance from the lamp, the measured lux values willl be less than the computed values in this overview as the measurements are then within the near field of the lamp.

Note II: the beam angle is more than 180 degrees, meaning that the size of a light spot can not be given; the numbers in the Ø50% column should not be considered.

Eulumdat light diagram

This light diagram below comes from the program Qlumedit, that extracts these diagrams from an Eulumdat file. It is explained on the OliNo site.


The light diagram giving the radiation pattern.

It indicates the luminous intensity around the light bulb. The directions or planes C90-C270 and C0-C180 give the same result as there is a symmetry around the 1st axis.

Illuminance Ev at 1 m distance, or luminous intensity Iv

Herewith the plot of the averaged luminous intensity Iv as a function of the inclination angle with the light bulb.


The radiation pattern of the light bulb.

This radiation pattern is the average of the light output of the light diagram given earlier. Also, in this graph the luminous intensity is given in Cd.

These averaged values are used (later) to compute the lumen output.


Intensity data of every measured turn angle at each inclination angle.

This plot shows per inclination angle the intensity measurement results for each turn angle at that inclination angle. There normally are differences in illuminance values for different turn angles. However for further calculations the averaged values will be used.

When using the average values per inclination angle, the beam angle can be computed, being 306º.

Luminous flux

With the averaged illuminance data at 1 m distance, taken from the graph showing the averaged radiation pattern, it is possible to compute the luminous flux.

The result of this computation for this light spot is a luminous flux of 147 Lm.

Luminous efficacy

The luminous flux being 147 Lm, and the power of the light bulb being 2.2 W, yields a luminous efficacy of 66 Lm/W.

Electrical properties

When a DC power source is used the power factor is always 1.0 as there is no blind power with DC voltages and currents.

Lamp voltage 12 V DC
Lamp current 185 mA
Power P 2.2 W
Apparent power S n.a.
Power factor n.a.

The Total Harmonic Distortion of the current is not present as a constant current flows.

Temperature measurements lamp


Temperature image (overview) of the light bulb

status lamp > 2 hours on
ambient temperature 24 deg C
reflected background temperature 24 deg C
camera Flir BCAM
emissivity 0.95(1)
measurement distance 0.10 m
IFOVgeometric 0.4 mm
NETD (thermal sensitivity) 100 mK

(1) The emissivity is set at 0.95 which is close to the value of the rought area of the printed circuit board.

The average temperature on the PCB is about 89 deg C. Touching the PCB does not harm as the heat capacity of the PCB is low.

Color temperature and Spectral power distribution


The spectral power distribution of this light bulb, energies on y-axis valid at 1 m distance.

The measured color temperature is about 3150 K which is warm white.

This color temperature is measured straight underneath the light bulb. Below a graph showing the color temperature for different inclination angles.


Color temperature as a function of inclination angle.

The measurement of CCT is measured for inclination angles up to 90º.

The beam angle is 306º, meaning a 153º inclination angle. In this area most of the light is present. The variation in correlated color temperature in the measured area up to 90º  inclination angle is about 2 %.

PAR value and PAR spectrum

To make a statement how well the light of this light bulb is for growing plants, the PAR-area needs to be determined. See the OliNo website how this all is determined and the explanation of the graph.


The photon spectrum, then the sensitivity curve and as result the final PAR spectrum of the light of this light bulb

parameter value unit
PAR-number 0.1 μMol/s/m²
PAR-photon current 1.1 μMol/s
PAR-photon efficacy 0.5 μMol/s/W

The PAR efficiency is 61 % (valid for the PAR wave length range of 400 – 700 nm). So maximally 61 % of the total of photons in the light is effectively used by the average plant (since the plant might not take 100 % of the photons at the frequency where its relative sensitivity is 100 %).

S/P ratio

The S/P ratio and measurement is explained on the OliNo website. Here the results are given.

The power spectrum, sensitivity curves and resulting scotopic and photopic spectra (spectra energy content defined at 1 m distance).

The S/P ratio is 1.1.

More info on S/P ratio can be found on the OliNo website.

Chromaticity diagram


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

The light coming from this lamp is inside the area designated with class B. This class B is an area that is defined for signal lamps, see also the OliNo website.

Its coordinates are x=0.4329 and y=0.4145.

Color Rendering Index (CRI) or also Ra

Herewith the image showing the CRI as well as how well different colors are represented (rendered). 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). Practical information and also some critics about the CRI can be found on the OliNo website.

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 57 is lower than 80 which is considered a minimum value for indoor usage.

Note: the chromaticity difference is 0.0048 indicates the distance to the Planckian Locus. There is no norm yet that states what the max deviation from white light is allowed to be. A reference with signal lights as a reference is given in the chromaticity diagram.

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 light bulb parameters measured: illuminance E_v [lx], the lamppower P [W] and the luminous efficacy [Lm/W].


Lamp voltage dependencies of certain light bulb parameters, where the value at 12 V is taken as 100 %.

The illuminance and consumed power do not vary significantly when the voltage is varied between 11-13 V.

When the voltage at 12 V varies with + and – 0.25 V, then the illuminance varies ≈ 0.1 %, so when abrupt voltage changes occur this effect is not visible in the illuminance output.

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] and the lamppower P [W].


Effect of warming up on different light bulb parameters. At top the 100 % level is put at begin

The warm up time is about 5 minutes. During that time the illuminance decreases with 23 %. The consumed power is measured separately and decreased with 8 %.

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