The Use of Johnson’s Criteria for Thermal Camera and Systems Performance

When customers are considering which thermal security camera or system to buy, one of the first questions asked of thermal imager manufacturers is usually: “At what distance can the IR camera detect a target?”. In other words, what is the camera’s ability to capture very small details at great distances? When thinking about effective surveillance, it is indeed a good criterion to differentiate one sensor from another.

No matter which manufacturer you are buying from, the answer given to this question will almost always include the “DRI ranges” expression. DRI refers to the distance at which a target can be Detected, Recognized, or Identified, based on certain universally accepted parameters. In order to select the right sensor for your defense, security, or surveillance needs, these DRI ranges have to be, first, perfectly defined, but also assessed with regards to globally adopted industrial standards. Enter Johnson’s criteria.

The Origin of Johnson’s Criteria

In 1958, at the first ever “Night Vision Image Intensifier Symposium”, John Johnson, a night vision scientist at the U.S. Army’s “Night Vision and Electronic Sensors Directorate” (NVESD), presented a paper named the “Analysis of Image Forming Systems”. Johnson’s paper defined a clear system with criteria and methodology for predicting an observer’s ability to find and assess targets using image intensifying equipment (such as thermal cameras), under various conditions. It worked well, and it was the first of its kind.

Johnson’s Criteria Definitions

Johnson’s model provided definitive criteria for calculating the maximum range at which “Detection, Recognition, and Identification (D, R, I)” could take place, with a 50% probability of success. (Orientation was also discussed, but this parameter is not used or recognized today).  Although newer methodologies for D,R,I exist today, such as NVESD’s “Night Vision Image Performance Model” (NV-IPM), the “Johnson’s Criteria” system was groundbreaking for its time, was the accepted standard in the defense industry for many years, and is still widely used in the security industry today.


Johnson defined “Detection” as the ability to subtend 1 TV line pair (+/- 0.25 line pairs) across the critical dimension of the subject (this translates to 2 pixels when using an LCD monitor). At the range that this occurs, regardless of target type, the observer could detect that a subject was in the field of view, 50% of the time. Today, many security camera companies loosely follow Johnson’s Criteria and define their camera’s “Detection” performance range as the ability to subtend either 1.5 or 2 pixels on the target, using various target sizes.


Johnson defined “Recognition” as the ability to subtend 4 TV line pairs (+/- 0.8 line pairs) across the critical dimension of the subject (this translates to 8 +/- 1 pixels when using an LCD monitor). At the range that this occurs, regardless of target type, the observer determines the type of subject, a human or a car for example, 50% of the time. Today many security camera companies typically define their cameras “Recognition” performance range as the ability to subtend 6 pixels on the target, using various target sizes.


Johnson defined “Identification” as the ability to subtend 6.4 TV line pairs (+/- 1.5 line pairs) across the critical dimension of the subject (this translates to 12 +/- 3 pixels when using an LCD monitor). At the range that this occurs, regardless of target type, the observer could detect the subject. Today many security camera companies loosely follow Johnson’s Criteria and define their cameras “Identification” performance range as the ability to subtend 12 pixels on the target, using various target sizes.


Johnson’s Criteria in the Security Industry

DRI ranges, expressed in kilometers (or miles), can usually be found in the specification table of infrared camera brochures, or in a description of the cameras features. While a very helpful jumping off point for narrowing down the options and homing in on the best systems, customers would be doing themselves a disservice to only look at DRI. This is because today the application of Johnson’s criteria varies somewhat across the security industry. In most instances, documentation uses simplified or modified versions of the criteria, but they do all generally follow similar rules.

Typically, most companies use twelve pixels on the target for identification, six for recognition, and two for detection (sometimes 1.5). However, the target size can vary greatly. Normally the defense industry “NATO” target size (2.3×2.3 meters) is used for calculating the performance range for detecting vehicles, but for a human target, various target sizes can be found. It is important when selecting your thermal camera to keep in mind that in any given document, the target size for a human can range from 1.7-1.83 meters tall and from 0.3- 0.75 meters wide, and factor this into your decision-making process.

The Need to look at the Bigger Picture

Because end-users often place a high value on the written specifications of the camera, marketing departments are under pressure to use performance calculations that make their cameras look better than the competitors. However, since these calculations typically do not take environmental factors into account, customers should ask their thermal camera providers to explain the other elements and benefits of each camera they are offering, and how they will perform in a variety of conditions. A modified approach that considers parameters such as these can better help in choosing the right thermal camera or system for your needs.

Never miss another fire alert with Vumii’s Sii AT Fire Detection Camera

NEWS- Vumii has just completed the integration of the Sii AT Fire Detection Camera with Digifort. This integration package ensures that high-risk (hot-spot) and fire alarms are triggered directly into the Digifort Video Management System (VMS) over IP. The IP VMS system is automated and can be managed, and reports accessed remotely, by users at approved IP’s. Any number of hot spot/fire alerts, alarms, and automation modules can be set, and your cameras feedback can even be viewed from your cell phone or tablet. info@vumii.com

Opgal is Unveiling the Thermal Security System of the Future

The future of thermal security cameras became reality as Opgal Optronic Industries Ltd., a leading manufacturer of thermal imaging systems, announced that they will be unveiling their new Sii™ OP thermal security camera later this month. Based on Linux OS, the Sii OP is defined as the first thermal camera with a truly open embedded software platform, boasting an incredibly easy installation and a dedicated Software Development Kit (SDK) for seamless third party integration.

Security cameras have come a long way in recent years. Once the realm of traditional CCTV systems, more security projects these days are built around thermal technology due to the 24/7, all weather detection capabilities of these devices. The need for better target detection has created a demand for thermal cameras that will be able to integrate with end-point analytics software that facilitates easier target detection and tracking.

“With our growing line of Vumii® thermal imaging systems, we are always seeking ways to reinvent thermal imaging and bring new technologies to market,” stated Amit Mattatia, President & CEO of Opgal. “The Sii OP introduces new standards to the security industry, by offering a cost effective option and a truly open platform to system integrators and software developers alike. This is yet a further proof of Opgal’s ability to leverage its vast experience in creating game-changing products.”

Equipped with both thermal and HD visible-light channels for day and night surveillance, Sii OP meets global ONVIF standards to ensure interoperability of hardware and software products for easy integration to both existing and new infrastructures, regardless of manufacturer.

Sii OP will be available from Opgal via a growing network of solution providers and distributors in all major countries, and will be offered with pre-integration to some of the leading VMS and analytics software in the market. Opgal will unveil the Sii OP at the IFSEC exhibition to be held June 21-23, 2016 at the ExCeL London, UK convention center.

Safer Airport Security Systems

Are airport security systems effectively protecting today’s travelers?

What safety measures actually make airports safer, vs. just making us “feel” safer?

Many people pass through international airports every day, and this high volume of people presents an irresistible target for terrorists. Add to this the destructive potential of a bomb on a large plane like the Russian Metrojet plane that exploded over Sinai in October of 2015, or the huge death toll possible when hijacked planes are used as weapons of destruction, as in the 9/11 attack, and the need for a layered and extensive approach to security measures becomes instantly clear.

The March 2016 suicide bombings in Brussels have renewed the debate over whether security checks at the entrance to airport terminals should be added along with other more stringent safety measures, or whether the security procedures currently in place are sufficient.

While some of the following measures may seem extreme, the airports using them are rated as some of the safest in the world:

  • Monitoring remote airport perimeters and critical areas with smart thermal and day/night camera systems
  • Using checkpoints to monitor vehicles entering the airport premises
  • Extensive screening of airport personnel
  • Monitoring the departures entrances and parking areas
  • Using military troops as backup for airport security
  • Using facial recognition software linked to international counterterrorism databases
  • Using software that reads facial expressions to determine malicious intent or extreme anxiety

Of course every airport is different and has different regional realities, needs, and concerns. What they all have in common is that they all operate around the clock, and they need security measures that do the same.

Smart thermal cameras are one such measure, and are at the forefront of land-based security technology. They improve situational awareness by providing round-the-clock intruder detection. Using these systems can increase security awareness without slowing down airport traffic; improving safety while cutting manpower costs in the long term.

So what is stopping international airports from anteing up in the security department? One reason is that large scale changes take time, and can seem costly. As a result we usually only see the short term solutions of governments and airport management, like temporarily stepping up security, law enforcement, and military presence in airports. These are effective measures for calming the public for the moment, but are not realistic long term solutions, as the costs have no long term return on investment.

The demand for an overhaul of long term security protocols to protect travelers and their families has become abundantly clear.  As it turns out, several international airports have already begun improving safety conditions by purchasing and installing smart thermal camera systems, and those that haven’t should consider following their example. The next time you decide to fly, what security measures will you want to see implemented in the airports you choose to fly in and out of?

Norway Fire Detection

Vumii Integrates Fire Detection into Firefighting Logistics System

Vumii has announced the integration of its Sii AT Fire Detection Camera into the Locus TransFire System in Norway. The integration of the thermal cameras enables a live thermal video feed, sending real time alerts with coordinates directly to the TransFire system to enable prevention and fast response to fires.

With the Sii AT’s Fire Risk Detection capabilities, a virtually unlimited amount of fire and heat sources can be detected, while avoiding false alarms from hot spots at the scene. Fire, or even an increase in heat occurring before fire actually starts, can be detected as far as 6 kilometers away. Visual alarms are displayed on the operator’s screen, while simultaneously sending alert signals for both fire and risk of fire over a wide area network, enabling emergency services to respond in a timely fashion.

Sii AT is part of Vumii’s broad line of thermal cameras and camera systems, allowing fast detection and reaction to a large amount of security threats and safety issues.

The TransFire system, developed by Locus Public Safety AS, a key supplier of logistics solutions to emergency services, is used by a large percentage of emergency call centers in Norway. Using detailed maps, the system helps with decision making and improves resource management, providing full integration of all fire-related systems to provide a complete firefighting logistics system. The Vumii Sii AT fire detection camera has been fully integrated into Locus’ TransFire system. Once the camera triggers an alarm, the information is fed into the fire command center and a fire truck is dispatched. The data is automatically plotted onto a map and displayed real time on a screen in the fire truck, ensuring that the team has the exact location and all necessary information before arrival at the scene.

The fire detection capabilities provided by Vumii are slated for use in a number of towns and facilities at risk of fire throughout Norway and further afield.