Passive, No Power, Low-Emissivity, Reverse Polarity

Juliet said to Romeo:

“What’s in a name? That which we call a rose, By any other name would smell as sweet;”
In other words, what we call something does not change its characteristics and function. The same is true for the various names attached to thermal film.
In this case, the names reflect more of a feature of the film rather than something different.
If you use or encounter any of these terms, be confident they all refer to the same film.
  • Passive
  • No Power
  • Low-E or Low Emissivity
  • Reverse Polarity

Overall, thermal film is very bad at giving off heat (thermal infrared energy) and very good at reflecting heat (thermal infrared energy).

To clear up any confusion, let’s examine each of these features so you can confidently utilize thermal film with your thermal devices.

1. Passive Film

The most frequently associated name with thermal film and all infrared films is PASSIVE.

The passive feature of the film refers to how the film reflects heat (infrared energy) in its surroundings. This is the opposite of “active” thermal panels which produce heat from electricity or chemical heaters.

Passive thermal film responds to the temperatures around it and reflects the temperatures off. Therefore the film appears cold.  Because the film appears cold and the temperatures around it are warm this creates a color contrast you see with your thermal device. While all the other objects in the scene appear warm, the passive film will always appear cold.

Depending on your palette settings, the film could appear white, black, or various shades of blue and purple.

2. No Power Film

Next to passive, No Power is a term used very often to describe thermal film. Initially when the film was first introduced for target training, “no power” was the name given. 

It is very simple. No Power means no power source is needed. 

No electricity, no batteries, and no chemical heaters are required for the film to function effectively. All you need is the film and a thermal device. The no power feature opens up a range of possibilities for different operational and training scenarios.  The film is lightweight and travels easy. 

In some cases when power is added to thermal film, if the power is disabled the film will continue to function. Thermal films do require a power source to work indoors. 

coyote black and white hot

3. Low Emissivity 

Emissivity is how efficiently an object will emit heat or thermal infrared energy. In the context of thermal films, which are poor emitters of heat, they typically have a low emissivity. 
Objects with low emissivity tend to reflect thermal energy rather than emitting it. Therefore a pronounced contrast is viewed with a thermal device. This is extremely beneficial when a distinct thermal signature is necessary.  
Most materials in the world have a high emissivity and low reflectivity, the exact opposite of thermal film. 

4. Reverse Polarity 

Reverse polarity is a little trickier concept to grasp.
All thermal devices have a color palette mode that includes among many others a white hot and black hot mode. White and black hot modes are used a lot when it involves weapons and movement.
If your mode is white hot, then everything cooler or cold will be black. If your setting is black hot, everything cooler or cold will be white.
When a user switches back and forth between white and black hot, this is called reversing the polarity on the device. While the temperature of the objects does not change, the white/black mode in the device can make it appear so.

4 Names = 1 Film

Romeo and Juliet would have been confused by all the names. Luckily you won’t face the same confusion.
When you hear or see the terms Passive, No Power, Low Emissivity and Reverse Polarity understand they all refer to the same thermal film.
If you have questions, connect with us and we would be happy to help.

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Thermal film is rapidly finding more and more applications anywhere thermal devices are used. This list is in no way comprehensive as thermal devices are implemented into more sectors and industries daily. 


Thermal Imaging Application Thermal Film Application
Thermal Weapon Sights Thermal Training Targets, Zeroing Targets, Thermal Camouflage, Personal Identification
Handheld Thermal Imaging Cameras Thermal Markers, Signs, Personal Identification
Airborne Law Enforcement Thermal Vehicle Markers, Signs, Personal Identification,
Pilot Navigational Equipment, Drones Landing Zone Demarcation, NIST Training
Consumer Thermal Imaging Cameras Reference markers on property
Industrial Thermal Imaging Cameras Building calibration markers for cameras and systems
Building Thermal Analysis Reference marker on buildings
 The Author

Tom Boyer profile picture

Since 2006, Tom has been the driving force behind IR.Tools, dedicated to delivering top-notch infrared solutions to the military, law enforcement, and sportsmen communities.

What began with a single infrared patch has blossomed into a comprehensive store featuring hundreds of IFF patches, vehicle IFF, an extensive suite of thermal training targets, and tools for drone pilots.

Beyond his innovative products, Tom is passionate about educating users on infrared technology and showcasing how advancements in IR can enhance their operations.

Tom holds an MS in Mechanical Engineering from the University of Maryland and an MBA from Regents University.

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