We are not sure how many people can’t understand the IES document. So what is IES exactly? Let me take you to the wonderful world of IES.

Popular science about IES

IESNA (Illuminating Engineering Society of North America)

is a technical association Founded in 1906,

IES document is light Distribution of light source (fixture) in electronic format.

It’s extension is “*.ies”, generally we call it IES document directly.

The meaning of IES document is defined and executed by IESNA, now it is

a default document format for storing spatial light intensity distribution of light source.

Computer software such as AGI, DIALux etc. can import and use IES document

The 2 most common expression of IES light Distribution

▲Representation of rectangular coordinates

▲Representation of polar coordinates

Diagram of IES

Does it makes your head explode when seeing the Note 1,Note 2, Note 3 in above figure……? Never mind, I will tell you their own meanings right away.

Note 1:

Peak Central Luminous Intensity: As can be seen from the figure, the Imax is roughly 930cd, the peak luminous intensity determines the lighting intensity and illuminance (Of course distance also counts as another important factor for illuminance).

Note 2:

50% of Peak Central Luminous Intensity: Here it is mainly for evaluating beam angle.

Note 3:

Beam Angle: Equal to the full angle (not half angle) under 50% of peak luminous intensity. Here we add the left and right angle together and get 64°. The beam angle determines the size of light spot, and it is closely related to lighting effect.

Note 4:

The unit of cd/klm in the bottom left corner means above data are based on 1000lm. That is to say, if your fixture’s output is 5000lm, then peak luminous intensity is 930*5000= 46500cd. ( cd/klm shows the capability of optical and lamp design.)

Note 5:

C0-C180 represents X axial plane, and C90-C270 represents Y axial plane ( this can be obviously clear in asymmetric beam angle).

Note 6:

Efficiency: Generally represents the efficiency of fixture or optical device. The higher the efficiency is, the better it is ( Efficiency reflects utilization factor for light, which is the most important reflection of capability).

Note 7：

10% of Peak Luminous Intensity: 1/10 Imax=93cd, which is mainly for the convenience of viewing filed angle in Note 8.

Note 8：

Filed Angle: Equal to the full angle under 10% of peak luminous intensity, in this figure it is about 90°.

Above are 8 important points of IES document in rectangular coordinates. In regards to polar coordinates, just get the important points according to polar coordinates.

▲ The function of IES document

▲Office lighting

▲ Supermarket lighting/warehouse lighting

▲Commercial lighting such as downlight etc.

▲Street lighting