Testing IR Illuminator Performance 2010By Benros Emata, Published Sep 05, 2010, 12:00am EDT (Research)
Low light can cause problems for surveillance cameras. IR illuminators may improve this situation. However, questions remain about the price and performance of IR illuminators.
Over the last year, we have examined a variety of issues and approaches for dealing with low light problems:
- Tricks manufacturers play with maximum exposure settings to 'improve' low light performance
- Using IP Thermal cameras such as the Axis Q1910 we tested
- Using built-in IR illuminators such as the Vivotek IP7361 we tested
Each of the above have their limitations, respectively: motion blur, high price and restricted camera choice.
In this test, we examine stand-alone IR illuminators that can be added to surveillance cameras to improve low light performance. Specifically, we purchased 3 inexpensive stand-alone IR illuminators via Amazon (the YY-IR100, YY-IR50, and the YY-IR30 that claim respectively 100m, 50m and 30m IR coverage).
We examined the following issues/aspects:
- How far can the illuminators really illuminate? Inside we show video samples of limitations of half the specified distance.
- What impact does reflectivity of the object has? Inside we show video samples of the dramatic differences between visibility and distance viewed for high reflectivity vs low reflectivity objects.
- Where should the IR illuminators be mounted? Inside we show video samples demonstrating placing IR illuminators perpendicular to the camera and using multiple illuminators.
- What bandwidth savings are acheivable? Inside we show video samples showing that bandwidth savings are likely achievable only in test, non-real world conditions.
Here are our key findings:
- The IR illuminator's actual maximum distance was significantly lower than the manufacturer's documented distance
- The maximum distance is highly dependent on the reflectivity of the object (e.g., a licese plate can be seen much further out than a person in a black shirt and jeans
- Bandwidth savings from IR illumination is dependent on the reflectivity of objects in a given scene
- The camera's field of view may need to be adjusted to match the illuminator's fixed horizontal beam width to eliminate dead spots
- Placing IR illuminators away from the camera will have trade-offs to the maximum effective coverage
We recommend strong consideration of the YYTrade IR illuminators for simpler, less critical applications. Although it lacks advanced features and performs under the specified maximum distance, the units provide clear benefits over no illumination at an extremely low price ($60 for the larger unit). When compared to a competitor's similar IR offering at approximately $780, the inexpensive IR model provides a savings of over 92%.
- All models have a specified IR wavelength of 850nm
- The YY-IR100 and YY-IR50 have a 30 degree horizontal angle
- The YY-IR30 has a documented 60-90 degree horizontal angle (this was not verified)
- All models integrate a low light sensor in the illuminator that turns off IR in daylight
- All models are built for indoor and outdoor use (IP65 rated enclosures)
- All models include an extra connector pigtail, to connect your own power cabling to the AC adapter
- The YY-IR100 consumes 12W, and includes an 8' long 12VDC adapter
- The YY-IR50 consumes 12W, and 12VDC adapter is only 3' long
- The YY-IR30 consumes 8W, and does not include a power adapter
- YY-IR100 has an array of 96 LEDs
- YY-IR50 has an array of 48 LEDs
- YY-IR30 has an array of 30 LEDs
Overview of Other Manufacturer Offerings
The YYTrade models should be compared to Bosch/ExtremeCCTV and Raytec. Both specialize in IR illumination, offering a significantly wider and more advanced offering than YYTrade.
For Bosch, the comparative IR series is the AEGIS UFLED [link no longer available] line, which has illuminators in both 850nm and 940nm wavelengths. The UFLED30-8BD operates at the 850nm wavelength, has a 30 degree horizontal angle, and 110m specified max distance.
In contrast to the YY-IR100, the Bosch model's LED array consists of 18 surface mount LEDs, up to 45W max power consumption, and input voltage that supports either 12 to 24 VDC or VAC. This model claims additional features like, automatic light control for longevity (they claim a 10 year product lifespan), even illumination to eliminate hotspots, and a link port to connect other illuminators as a master / slave configuration. The online price is approximately $780 USD.
Raytec's similar model is in the RayMax 100 Fusion [link no longer available] series, which also has 850nm and 940nm wavelength selections. The RM100-F-30 works in 850nm wavelength, has a 30 degree horizontal angle, and 80m specified max distance.
Raytec differs in that it allows manual power and photocell level adjustment, photocell placement (located behind the unit instead of in front as part of the LED array), has an integrated power supply, and input voltage of 12 to 24 VDC or VAC. They also claim automatic LED light control for longevity (projected 10 year product lifespan). The online price is approximately $776 USD.
Examining the YY-IR100 Illuminator's Maximum Distance
The YY-IR100 specificies an effective maximum distance of 100 meters. According to YYTrade, they verified the distance for the YY-IR100 in an enclosed warehouse test. In our test, we placed the IR illuminator in a common outdoor low light scene with less controlled variables. We placed three day/night IP cameras with the same field of view in front and below the IR illuminator. Our subject started close and walked away from the cameras so we could observe to what distance he would disappear from the IR light.
Key points include:
- In the scene, the subject is wearing black clothing, a color that absorbs more light than reflects
- At 30 meters (100 ft), the subject just starts to become difficult to see on some cameras
- At 44 meters (145 ft), the subject is becoming harder to see on all cameras
- At 49 meters (160 ft), the subject cannot be seen on all cameras
Our test shows that in an outdoor environment, The YY-IR100's maximum effective distance (49 meters) is half of the manufacturer's listed specification (100 meters).
The Impact of IR Light Reflectivity and Absorption
The following screencast examines reflectivity, absorption, and diffusion's impact on IR illuminated scenes.
Key points include:
- All objects react to light by a combination of absorption, diffusion & reflectivity
- Colors and materials reflect and absorb light differently
- In an IR illuminated scene, we have our subject hold license plates as he walks away from the camera
- As the subject walks away from the camera, his black clothing absorbs more light than it reflects back
- At 43 meters (140 ft), the subject is barely visible, but the license plates are still reflecting light
- Dark colors absorb more light, while light colors are more reflective
- Outdoor scenes may have less objects that reflect light back to the camera
IR Illuminator Physical Positioning
We examine what is the most appropriate physical placement for IR lighting. In the following screencast, we look at the most common lamp placement, how to adjust for the best image, and the trade-offs of placing IR lighting away from the camera.
Key points include:
- The most common placement of IR lighting is above and behind the camera, pointing the beam towards the camera's field of view
- It is important to have the IR light cover the entire camera's field of view; If camera's field of view is wider than IR coverage, dead spots will appear on corners
- Specify an IR illuminator that matches the camera's field of view, or if possible, adjust the camera's zoom to match IR coverage
- We test the effectiveness of placing an IR illuminator perpendicular to the camera so the light shines horizontally across the 30 meter (100 ft) mark
- One trade-off of perpendicular placement is the subject is not evenly lit
- Another trade-off is effective coverage of the IR light is wasted
- Although another option is to use two illuminators (one perpendicular and co-located with camera), potential IR coverage is still wasted with the farther illuminator
- Traditional lighting may be sufficient for lighting away from the camera
Some manufacturers claim their IR products provide large bandwidth savings over an IP camera network- some even claim that their illuminator can provide a 90% bandwidth savings.
The claims come from the fact that in a low light scene, the gain level within a camera produces a certain amount of noise, and this noise increases a video stream's bit rate. When illuminators are applied, the IR light washes out the camera noise, resulting in the bit rate to drop.
In the following screencast, we discover that IR light's effect on bit rate in a low light scene is dependent on specific environmental factors.
Key points include:
- Manufacturer IR bandwidth test results may be from testing in closed, controlled environments
- We place a camera and an IR illuminator in a small indoor low light environment at approximately 0.3 lux
- The indoor low light video has a high amount of camera noise and the bit rate is at 2Mbps
- When the IR light is turned on in the indoor scene, the bit rate drops to 240kbps- which provides an 88% bandwidth savings
- The environment in the indoor scene is mostly white, resulting in high reflectivity of the IR light
- The reflectivity of IR light in the environment washes out the camera noise, which drops the bit rate
- We move our tests to an outdoor low light environment at approximately 0.2 lux
- The outdoor video has a high amount of camera noise and the bit rate is at 3Mbps
- As we turn on the IR lighting, then turn it off, no significant change in the bit rate is observed
- The lack of reflective objects in the scene allowed the camera noise to persist, resulting in no effective drop in bit rate
- Bandwidth savings is dependent on an environment's reflectivity and scene complexity
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