When specifying reflective label materials, you may have encountered the term ‘retroreflective’; and as a result, wondered how it differs from just ‘reflective’.
Light reflection occurs as different types, but retroreflection is unique.
To better understand let’s take a look at the different types of reflection, and learn why retroreflection is the type we want to specify for our safety signs and identification markers.
Reflection vs. Emission
Emitted light is its own source, and consumes energy. Examples of emitted light would be an electric light bulb or a gas flame.
Reflection cannot emit, or in other words, create light. Reflection can only take light from another source and bounce it in other directions.
Without an external source of light, reflective surfaces reflect nothing.
When considering reflected light, it’s important to consider the ‘incident angle’; or in other words, the direction from which the light aimed at the reflective surface is coming.
We’ll see why the incident angle is important when we consider the basic types of reflection.
Three basic types of reflection
Diffuse reflection occurs when light strikes rough or textured surfaces, and reflected light from these types of surfaces scatters in all directions.
The result reflects as a harsh glare, and regardless of the incident angle of the light being reflected, not all of that light is returned to the person viewing it.
Examples of diffuse reflection are when vehicle headlights and street lighting reflect off the wet pavement, or as light reflecting from water vapor in the air in the form of heavy, low fog.
Mirror reflection is exactly as its name suggests… like light directed at a mirror. Light directed at a mirror surface is reflected at an equal, but opposite angle from the incident angle of the light aimed at it.
This is why when you stand directly in front of a mirror surface, you see yourself. But if you stand at a wide angle to one side, you cannot see yourself. A person at the same angle on the other side, however, would see your image in the mirror.
Retro? No, not like a reflection of past style as modern usage of the term might suggest! The term is used here as a prefix from Latin meaning ‘back’, or ‘backwards’.
Retroreflective materials are designed with reflective lens elements that direct most or all of the light directed at them back in a narrow beam and in the same direction as the incident light.
This means that the light source directed at a retroreflective surface from headlamps of a car the viewer is occupying, a flashlight held by the viewer, or area lighting coming from the same general direction as the viewer, will be reflected back to the viewer’s eyes.
This adds a level of nighttime visibility for safety sign messages, conspicuity when trying to highlight objects that need to be avoided, or spot equipment and easily view asset identification markers in the dark.
Reflective performance is defined by brightness, which is an instrument measurement of the light reflecting efficiency of a surface.
Reflective performance is also defined by angular capability towards the entrance angle of the incident light source, and the angular ‘width’ capability at which it can return that light.
Together, these factors form a ‘cone’ of reflected light that is termed the ‘observation angle’.
Retroreflective sheetings are available in different grades and types, and may be designed for narrow, long distance viewing angle performance; or closer, wide viewing angle performance.
It is generally expected that viewers will be in close proximity when they encounter utility assets that may represent a hazard, and the incident light source may be at an offset angle from the viewer.
Therefore, retroreflective materials designed for performance at wider observation angles are best suited for safety signs and identification markers used for utility asset applications.
The Electromark advantage
Electromark exclusively uses traffic sign grade retroreflectives for our reflective products and offers several different types that deliver the wide angle viewing performance that best suits your applications.
We understand and use the necessary translucent inks so that the printed colors don’t block the reflective properties, and exhibit the same type of reflection as the unprinted areas of your sign or label.
If you have any more questions or comments, feel free to reach out to our customer service team.
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