IR Camera Reflection Test

All that might stand between good video and bad in your IR dome is a ring of foam rubber, keeping infrared from reflecting into the lens. Installers may have seen this small part on any number of cameras,

The gif below shows removing and replacing this part on a Hikvision minidome:

But what does this seemingly minor component do? How much effect could it really have? We answer these questions in this report.

Small Part/Huge Difference

In short, without this piece in place, there are two key significant problems:

• Reflection: Integrated IR reflects directly back into the lens, obscuring practically the entire view of the camera and showing the lens/LEDs reflected back onto the dome.
• Poor exposure adjustment: The camera attempts to reduce exposure to compensate for the bright illuminator, reducing visibility, or as in the example below, nearly eliminating visibility in most of the scene.

With Ring In Place

With the ring in place (as normal), the subject is clearly visible in the center of the scene, exposure adjusts properly, and the scene is more evenly illuminated.

Out of Place

Removing that small part simply destroys the image as shown in the gif below.

In this example, the subject begins at ~10' from the camera, but can't be seen until he is ~2-3' away. Even at that distance, few details are available through the LEDs/lens reflected on the inside of the dome.

Practical Effects

Note that neither we nor manufacturers recommend moving or removing these dividers found on IR cameras. This test is intended simply to show the net benefit they bring.

However, there are two practical scenarios where this may be worth keeping in mind:

1. Mis-fitting rings/dividers: In some cases, these foam components may dry out or become damaged during install, reducing effectiveness and allowing IR to leak back to the lens. Repositioning or replacing the ring may reduce or remedy these issues.
2. Older cameras: Some older IR domes did not include dividers such as these, or included less effective means of isolating the lens from illuminators. This was a common complaint in earlier IR domes, but less frequently in current models. Those with cameras experiencing these issues might consider adding some division between lens and illuminator as a last resort (such as foam tubing cut to size or even cardboard).

Other Cameras

All of the IR dome cameras in our tests included some type of physical division between the lens and IR illuminators. On most, it is a foam rubber ring similar to the one shown here. On others, it is rubber or plastic. Most cameras do not allow this component to be removed/replaced.

Some examples are shown here: