1. What is the beam angle?

Angle Definition in the context of beam angle refers to the method of specifying the angular spread or divergence of a light beam, typically expressed as the angle between points where the beam intensity drops to a specified percentage of the maximum.

The beam angle is generally for lamps, but it can also be used for reflective light sources. It's just that this standard does not specify which case uses 10% and which case uses 50%. In practical applications, CIE (International Commission on Illumination) recommends that the beam angle be the radial angle of 50% of the maximum light intensity; while IES (Illuminating Engineering Society of North America) recommends that the beam angle be the radial angle of 10% of the maximum light intensity. For non-fully symmetrical lamps, such as in the cross section of C=0° (and) in γ=0°, the angle of the beam with a light intensity of 10% of the peak light intensity may be different, that is, the beam angle of the lamp in the horizontal and vertical directions may be different. Generally speaking, the beam angle range of downlights is 10°~60°, and the beam angle of ceiling lamps is about 140°.The beam angle of the lamp is reflected on the illuminated wall/ground as the size of the light spot and brightness. The larger the beam angle, the smaller the central light intensity and the larger the light spot. Conversely, the smaller the beam angle, the greater the ambient light intensity and the worse the scattering effect.

2. How to choose the beam angle?

In addition to practical lighting, lighting design can also create a sense of atmosphere. Different beam angles should be selected for illumination in different spaces. It is necessary to calculate the impact of the spotlight's distance from the wall and the ground on the light spot.

Let’s assume that under the same floor height conditions (for example, the floor height of a home environment is generally about 2.8 meters), if the light is also irradiated from the top of the ceiling onto the desktop, the size of the light spot formed on the desktop and the light intensity at the center position are different due to different beam angles, and the feeling will be different. The following figure is a comparison between the design drawing and the actual picture:

It can be seen that the light perception created by different beam angles is not the same. The beam angle should be selected according to the actual irradiated object and the usage scenario.

3. Application of beam angle 

different beam angles have different applications. For example, a narrow beam can easily produce a high key lighting coefficient, which gives a strong visual impact with its strong contrast between light and dark, and can catch people's attention at the first time. However, too high a contrast will make it difficult for the observer to see the details of the illuminated object, and if the light spot is too small, the illuminated object will not be fully illuminated. Of course, in practical applications, we must also consider factors such as the distance, direction, and ambient brightness of the lamp projection.

Common beam angles are 10°, 24°, and 38°. Let's take a look at the light distribution curve diagrams of the three beam angles:

It can be seen that the 10° angle lamp cup has a very small irradiation range, but the central light intensity is the largest, which can form a strong contrast on the irradiated surface; the 38° angle lamp cup has a large irradiation range, but the central light intensity is the smallest, and the light spot formed on the irradiated surface is softer; the 24° angle effect is between 10° and 38°. That is to say, for lamp cups of the same power, the larger the beam angle, the smaller the central light intensity, and the softer the resulting light spot. On the contrary, the smaller the beam angle, the greater the central light intensity, and the harsher the resulting light spot.

In actual application, different beam angles have their own uses. In the above picture, 3 different beam angles produce 3 different effects on the statue.The 10° angle gives a strong visual impact with its strong contrast between light and dark, which can catch people's attention at the first time, but we found that: under the strong contrast between light and dark, we can't see the details of the plaster statue clearly, and because the beam angle is too small, the statue is not fully illuminated. 24° is much better than the 10° beam angle. It can well show the texture of the plaster and the demeanor of the figure statue, and also has a good visual impact.38° lighting statues produce a soft and delicate effect, making it easier to observe the details of the statue. However, due to the large beam angle, the background and the statue are mixed together, which is difficult to attract people's attention.This is a comparison of different beam angles at the same power and the same projection position. In actual application, we must also comprehensively consider parameters such as projection distance, direction, and ambient brightness, and choose different lamp cups according to needs. If the ambient illumination is high, a beam angle of 10° may be required, because the ambient light can make up for the area that is not illuminated on the statue, and the strong light and dark contrast formed by the 10° beam angle on the statue has a good visual impact. If the installation distance is close, 38° should be selected. As the distance becomes shorter, the illumination range will also become smaller, and the illumination will also increase. Similarly, if the projection distance becomes farther, a beam angle of 10° should be selected.

Thanks for reading:)

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