LEDITLIGHT – 1×3 Watt CREE XP-E – extra warm white – mr11

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

lil-mr11_1x3w-cree-2700k presents a 1 x 3 W spot ledlamp with cree led. The fitting is in MR11 format.

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 2748 K Warm white
Luminous intensity Iv 173 Cd Measured straight underneath the lamp.
Illuminance modulation index 0 % Measured straight underneath the lamp. Is a measure for the amount of flickering.
Beam angle 41 deg 41º for all C-planes since the lamp is symmetrical along its 1st axis.
Power P 2.6 W
Power Factor n.a. A DC power supply was used to test. This means that there is no blind power.
THD n.a. % Total Harmonic Distortion is not present due to the usage of a DC Voltage which results in a DC current.
Luminous flux 100 Lm
Luminous efficacy 39 Lm/W Note: a DC power is used and so no power supply is included that normally converts 230 V AC into 12 V DC.This means that this luminous efficacy number is without the effect of a power supply which would otherwise lead to additional power consumed.
CRI_Ra 81 Color Rendering Index.
Coordinates chromaticity diagram x=0.4541 and y=0.4061
Fitting MR11 This lamp can be connected to a 12 V DC or AC voltage.
PAR-value 1.7 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 0.4 μMol/s/We The total 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 1.2 This factor indicates the amount of times more efficient the light of this light bulb is perceived under scotopic circumstances (low environmental light level).
D x H external dimensions 36 x 37 mm External dimensions of the lamp, without pins.
D luminous area 18 mm Dimensions of the luminous area (used in Eulumdat file). This is the surface of the smalles circle around the leds at the front of the lamp.
General remarks The ambient temperature during the whole set of measurements was 25.5-26.5 deg C. The temperature of the housing gets about 37 degrees hotter than ambient temperature.
Warm up effect: during the warm up time the illuminance decreases with 11 % and the consumed power with 6 %.

Voltage dependency: the power consumption and illuminance vary insignificantly when the power voltage varies between 11-13 V DC.

At the end of the article an additional photo.

Measurement report (PDF) tbc
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 18 mm ≈ 100 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.

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. All the planes give the same results as the lamp is symmetrical along its 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 41º for all C-planes looked at.

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 100 Lm.

Luminous efficacy

The luminous flux being 100 Lm, and the power of the light bulb being 2.6 W, yields a luminous efficacy of 41 Lm/W.

The reported efficacy is for the led only, without an eventual power supply needed to transform 230 V AC into 12 V DC or AC. Such a power supply would normally lead to additional power consumption.

Electrical properties

The lamp was used on DC power and therefore no blind currents.

Lamp voltage 12.0 V DC
Lamp current 214 mA
Power P 2.6 W
Apparent power S n.a. VA
Power factor n.a.

Temperature measurements lamp


Temperature between two fins

Between the fins the emissivity is close to 0.95. This holds when the width between the fins is at least 5 times less than the depth of the space. This way there is little reflection.

status lamp > 2 hours on
ambient temperature 25 deg C
reflected background temperature 25 deg C
camera Flir T335
emissivity 0.95(1)
measurement distance 0.2 m
IFOVgeometric 0.3 mm
NETD (thermal sensitivity) 50 mK

(1) See text for explanation.

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 2750 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 55º. Beyond that angle the illuminance was very low (< 5 lux).

The beam angle is 41º, meaning a 20.5º inclination angle. In this area most of the light is present. The variation in correlated color temperature in this area is little more than 1 %.

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 1.7 μMol/s/m²
PAR-photon current 1.0 μMol/s
PAR-photon efficacy 0.4 μMol/s/W

The PAR efficiency is 65 % (valid for the PAR wave length range of 400 – 700 nm). So maximally 65 % 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 1.2.

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 indicates an area that is defined for signal lamps, see also the OliNo website.

Its coordinates are x=0.4541 and y=0.4061.

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 82 is higher than 80 which is considered a minimum value for indoor usage.

Note: the chromaticity difference is 0.0011 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.

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], the lamppower P [W] and the luminous efficacy [lm/W].


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

The warm up time is about 20 minutes, during which the illuminance decreases with 11 % and the consumed power with 6 % (separately measured).

Measure of flickering

An analysis is done on the measure of flickering of the light output by this light bulb. See the OliNo site for more information.


The measure of fast illuminance variartion of the light of the light bulb

parameter waarde eenheid
Flicker frequency n.a. Hz
Illuminance modulation index 0 %

The illuminance modulation index is computed as: (max_Ev – min_Ev) / (max_Ev + min_Ev).

Note: the modulation is so small that the flicker frequency is not relevant and even maybe not correct. Looking at the image it does not look like a stable frequency.

Additional photo

Close up of the led.

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