We get this question a lot. How much light is okay for my tubes? The answer is simple but requires context.
All wavelengths night vision is sensitive to can/will damage tubes due to how they function. This is why there are minimum stated lifespans of operation time.
The main factors which determine how quickly a tube can be damaged are:
•Energy
•Concentration
•Duration
Energy can be thought of as a lumen equivalent we’re familiar with for flashlights. How much energy is being emitted. Concentration would be how focused the energy is - think candela. Duration is the amount of time exposed.
Now let’s put this into context with an analogy to simplify this as much as possible. We will relate the image intensifier to the palm of your hand. Energy will be weight. Concentration will be surface area.
Imagine the palm of your hand open flat against a table. Now place a 20lb brick on it. It will be uncomfortable, but you can sustain this for a while, as the energy spread over a larger surface area isn’t immediately damaging. This represents a light source or environment that isn’t concentrated. Now imagine the same scenario but with the brick placed on top of an upright needle on your palm. It will immediately cause damage due to the concentration of force/energy on the smaller surface area. This would be like a direct laser hit on an intensifier.
So to answer the question, all light that night vision is sensitive to can/will damage tubes. What determines how quickly they are damaged is dependent on a combination of factors.
We can think of this in reverse too. The more concentrated an energy source is the less time it takes to damage an intensifier. The less concentrated the longer it would take; both also depending on the amount of energy itself. Example: streetlights are fine as long as you don’t stare at them for a long duration. They’re bright but the energy isn’t very concentrated, even at the emission area. The shorter duration of glances past this source are fine. You may induce a temporary burn or streak but it will subside during use rather quickly.