How to Measure IR Illumination

By: John Honovich, Published on Feb 15, 2012

Using IR for night time surveillance is a popular choice. The added non visible light can improve image quality when ambient street or visible lighting is absent. However, adding the right amount of IR light can be challenging. Add too much and the scene is over exposed. Add too little and the scene is still too dark. Measuring IR illumination is a useful way to get it just right and to identify invisible problems. In this report, we explain how to do so.

The Typical Approach

Typically, when you want to choose IR illumination, you look at a manufacturer's specification for maximum distance and beamwidth. The maximum distance indicates how far you can 'see' from the illuminator while the maximum beamwidth signifies how wide you can view (e.g., 10 degrees, 30 degrees, etc.)

The challenge in those numbers, like camera manufacturer minimum illumination ratings, are hard to use and compare. They are not standardized or vetted. The specified levels may not match actual performance plus comparing different manufacturers based on specs is unlikely to be accurate.

Day Time Approach

During the day or with conventional camera setups, if you wanted to measure light levels, you would use a lux meter (and you should use a lux meter - see our tutorial on using lux meters). Knowing the exact (visible) light levels can really help knowing how well a camera will work in a given scene.

Unfortunately, 'regular' lux meters are not designed to measure IR illumination. If you have an IR illuminator on in the dark and hold up your 'regular' lux meter to it, it will likely register 0 - an unhelpful and misleading result.

Specialized Meters to Measure IR

Specialized meters do exist that measure IR light. The big downside is that these options are much more expensive (thousands of dollars) and scientific oriented.

We did find one that was relatively inexpensive (~$500) and field usable - the Coherent LaserCheck [link no longer available]. We bought one and did a test. Here is a sample image of us demonstrating it.

Get Notified of Video Surveillance Breaking News
Get Notified of Video Surveillance Breaking News

Inside, we provide two video screencasts showing how to use this meter in action and how to best optimize your use of IR illumination.

Key Metrics

In our field testing, the optimal range of IR light or producing clear evenly exposed surveillance video is about 1-5. When measuring IR, the metric used is microwatts/centimeter squared or uW/cm2. As such, this is 2-5 uW/cm2.

If you have substantially more than 5 uW/cm2, the result will likely be an overexposed image. Think of the illuminator like a car's headlamp. The IR illuminator is typically a narrowly focused beam used in an overall dark area. When the beam is too powerful for the camera, the result is overexposed video.

The exact amount of light that is optimal for a camera depends on a number of factors:

  • The amount of visible light (i.e., is it 0.1 lux or 0.5 lux visible light - more visible light, less IR needed)
  • The visible light sensitivity of a camera (i.e., does the camera 'good' or 'bad' at low light in general)
  • The camera's responsiveness to IR (which might vary modestly among D/N cameras)

For instance, cameras that performed the best in our low light shootout would need less IR light (closer to 2) while those that did poorly would need more (closer to 5).

Practical Uses of Measuring IR

In our testing and usage, we found a number of practical benefits of measuring IR illumination:

  • Benchmarking camera performance:
  • Benchmarking IR illuminator performance: Knowing exactly how much IR illumination is generated at a specific distance is more useful than just a manufacturer specified range. For instance, if you test an illuminator and power output at 100 feet is only 1.1uW/cm2 that tells much more than a 150 feet range specification.
  • Adjustment: Because IR light is invisible, it is hard to know when it is optimally aligned. You can view video on a monitor but we found it far more accurate to take IR readings as we adjusted the illuminator (both vertical and horizontally).
  • Maintenance: Over time, image quality may degrade. Using a meter can help determine if the IR illuminator simply was shifted out of alignment or if it is a result of a decrease in power output from the illuminator as the LEDs/illuminator ages.

Basic Usage

In the video below, we demonstrate how the basics on how to measure IR illumination:

Advanced

In this video, we look at how to setup the meter including specifying the correct illumination range to measure:

Image Samples with Measurements

Take a look at the image below for a sample IR measurement. The reading is 7 uW/cm2 at 30 feet from the camera and IR illuminator. The subject is clearly overexposed as there is too much IR illumination for this camera's light sensitivity and the scene's light level. Note: that not all cameras will be overexposed at 7 uW/cm2. For instance, the camera used here is the Bosch 1080p which is strong in low light even without IR. By contrast, an Arecont 5MP might need 7 uW/cm2 or even greater IR illumination.

Now, we have the same camera with the subject and measurement at 100 feet. Here the IR illumination is down to nearly 1 uW/cm2. Unlike the close up shot, our subject is fairly evenly illuminated. The practical problem is that the FoV is too wide to capture much details. Of course, this could be adjusted by narrowing the camera's FoV.

Example of Varying IR Power

Some camera manufacturers have recently started promoting cameras with built in IR that automatically adjust their output power. This addresses the overexposure problem we showed in the last section. In this Samsung demo video, it shows how the camera dynamically adjusts the IR power output to optimize the power level for the subject's location in the scene.

We do not know how well this works and are showing this primarily to reinforce the important of optimizing the output power to ensure proper exposure of subjects when using IR.

3 reports cite this report:

Raytec Standard for Video Surveillance Lighting on Dec 10, 2015
Illumination specialist Raytec has released what it describes as the "industry’s first ever Lighting Standard for Video Surveillance Applications –...
Avigilon Real Time Exposure And Gain on Feb 24, 2015
Knowing how exposure and gain impact image quality, bandwidth, and camera performance can useful in installation and troubleshooting. Very few...
Testing Day vs Night With IR on Dec 09, 2014
IR illumination helps. When it gets dark, especially real dark, with no nearby artifical lighting, pretty much every surveillance camera (even...
Comments : Members only. Login. or Join.

Related Reports

IR Surveillance Camera Guide on Feb 06, 2020
Integrated infrared (IR) cameras are everywhere in 2020, but not all IR is created equal, with many differences in coverage, overexposure,...
Integrated IR Camera Shootout 2020 - Avigilon, Axis, Bosch, Dahua, Hanwha, Hikvision, Panasonic, Uniview, Vivotek on Jan 30, 2020
The best and worst cameras tested in this IPVM shootout showed major differences in quality and performance. While many view IR as being a...
Color Low Light Mega Camera Shootout - Avigilon, Axis, Bosch, Dahua, Hanwha, Hikvision, Panasonic, Speco, Sony, Vivotek on Nov 12, 2019
This is the biggest color low light shootout ever, testing 20+ super low light models from 10 manufacturers: Increasingly, each manufacturer...
Biggest Low Light Problems 2019 on Nov 08, 2019
Over 150 integrators responded to our survey question: "What are the biggest problems you face getting good low-light images?" Inside, we share...
Wide Dynamic Range (WDR) Guide on Oct 01, 2019
Understanding wide dynamic range (WDR) is critical to capturing high quality images in demanding conditions. However, with no real standards, any...
Hikvision ColorVu Camera Tested on Jun 24, 2019
Hikvision says their new ColorVu line captures "vivid chromatic images in darkness", with unconventional white light illuminations whereas most...
Vivotek 20MP Multi-Imager Tested on May 30, 2019
Vivotek has released their latest repositionable multi-imager camera, the MA9321-EHTV, a 20 MP model claiming "Supreme Night Visibility", "Optimal...
Speco Ultra Intensifier Tested on Apr 22, 2019
While ISC West 2019 named Speco's Ultra Intensifier the best new "Video Surveillance Cameras IP", IPVM testing shows the camera suffers from...
Startup Spectral Edge RGB+IR Claims "Unique Low Light Performance Tech" on Apr 03, 2019
This UK startup, born out of university research, is boldly proclaiming that they deliver "Unique low light performance tech for video surveillance...
Axis 5MP P Vs Q Camera Shootout (P3227-LVE vs Q3517-LVE) on Apr 02, 2019
While Axis' Q3517-LVE tested well, it is one of Axis' most expensive dome cameras, over $1,000 USD. Because of this, members asked us how it...

Most Recent Industry Reports

Genetec Drops Support for Dahua and Hikvision on Jun 01, 2020
Genetec has dropped support for Dahua and Hikvision, citing US blacklisting and ONVIF conformance blockage, the company informed partners in an...
Dotty "Hot Or Not" Elevated Body Temperature App Tested on Jun 01, 2020
What if you could take an existing phone or tablet and transform it into "fever camera"? That is what DottyAR is doing with their strangely named...
Optris "Fever Screening Systems" Examined on Jun 01, 2020
German manufacturer Optris has been building temperature measuring instruments for industrial manufacturing for over 15 years, and thermal cameras...
Fever Camera Sales From Integrators Surveyed on Jun 01, 2020
Fever cameras are the hottest trend in video surveillance currently but how much are integrators selling them? 220 integrators answered the...
"Fever Camera" Show Starts Tomorrow on May 31, 2020
IPVM is excited for the world's first "Fever Camera" show, to be held this Tuesday, June 2nd and Wednesday the 3rd from 11am to 3pm EDT, giving you...
Proxy Presents Mobile Credentials For BLE Devices and Access on May 29, 2020
Proxy presented Mobile Credentials For BLE Devices and Access at the May 2020 IPVM Startups show. Inside this report: A 30-minute video...
ISC West 2020 Moves To The Basement on May 29, 2020
The twice cancelled/postponed show will now not only be held in a different month (October) but on a different floor, moving down to the...
Integrators Avoiding Coronavirus Air Travel on May 29, 2020
IPVM asked integrators if air travel is part of their 2020 plans to see how significantly Coronavirus will impact future...
Viakoo Presents Cyber Hygiene for Cameras on May 28, 2020
Viakoo presented its 'Cyber Hygiene' and 'Service Assurance' products at the April 2020 IPVM New Products show. Inside this report: A...
Seek Scan Thermal Temperature Screening System ReTested on May 28, 2020
Now that IPVM has tested Dahua, Hikvision, and Sunell, we are returning to Seek, the first blackbody system we tested and retested it with our...