Laser pointers have become quite popular gadgets for use in presentations, playing with pets, astronomy, and more. The two most common colors for laser pointers are red and green. But which color is better for different uses? Here we will compare red and green laser pointers across various factors to help you decide which is best for your needs.
Background on Laser Pointers
Laser pointers are small handheld devices that emit a narrow, focused beam of coherent light. This bright point of light can be useful for highlighting items of interest or drawing attention to details. The first laser pointers were developed in the 1980s and used helium-neon gas lasers that emitted light in the red portion of the visible spectrum at a wavelength of 633 nanometers.
In the 1990s, diode laser pointers were invented. These used semiconductors rather than gas and could operate at different wavelengths, allowing for production of green laser pointers with light at 532nm wavelength. While less expensive helium-neon red lasers remain popular, both colors are now widely available.
Visibility of the Laser Dot
One of the most important considerations when choosing between a red or green laser pointer is the visibility of the bright spot produced by the laser. This will depend on the background and ambient lighting conditions where you plan to use it.
The sensitivity of the human eye peaks in the green portion of the visible spectrum. As a result, the green laser dot appears brighter to our eyes and is generally more visible than a red dot of the same power output. Green also offers higher contrast against most backgrounds. This makes green laser pointers easier to see in a brightly lit room and ideal for use in presentations.
Red laser pointers work better in relatively dark environments. The red wavelength does not reflect as well off projection screens, so the dot is more challenging to see in a fully lit room. But when used against a dark background or under the night sky, the red beam is quite bright and visible.
Safety
Laser pointers can be hazardous if improperly used. Exposure to laser light can potentially damage the eyes, so it is important to select a laser color that matches the planned usage in order to minimize risks.
In general, green laser pointers are considered more hazardous than red. The sensitivity of the eye peaks in the green spectrum, meaning the light from a green laser is focused more tightly on the retina. Green lasers are therefore restricted to lower power outputs in many regions. Typical green laser pointers are limited to 5mW power, while red can be up to 90mW.
The tighter focus of green light also means it can reflect more strongly off shiny surfaces. Stray reflections are more likely to cause temporary flash blindness. Red light tends to diffuse more and is less prone to dangerous reflections.
For presentation purposes in controlled environments, both colors are acceptably safe when used properly and not directed at eyes. But for playing with pets or stargazing where accidental exposure is more likely, red is the safer choice.
Range and Brightness
Higher power laser pointers can project the beam further and generate a brighter dot at long distances. Green’s ability to focus tightly gives it some advantages for range over red lasers of the same stated power.
In a 5mW red vs green comparison, the green laser tends to appear visibly brighter at distances over 50 feet. But legal red laser pointers up to 90mW can project quite far and bright. The table below compares the approximate maximum distance a visible dot can be produced for common laser pointer power levels.
| Laser Color and Power | Maximum Visible Distance |
|---|---|
| 5mW Green | 1600 feet |
| 5mW Red | 1000 feet |
| 10mW Green | 2300 feet |
| 90mW Red | 7000 feet |
For short distances under 50 feet, there is minimal difference between 5mW red and green. But for pointing out stars and constellations at night, a 90mW red laser can project quite far with excellent visibility.
Natural Filtering of Laser Colors
The atmosphere filters different colors of light as they pass through, which can impact the visibility of laser pointers used outside in the daytime. Shorter blue and green wavelengths are more easily scattered by air molecules and diffuse more quickly over distance than longer red wavelengths.
As a result, daylight rapidly washes out green laser light. The beam becomes difficult to see within a few hundred feet unless the sun is obscured by clouds or fog. By contrast, red laser pointers remain reasonably visible for a kilometer or more under clear sky.
At night or in darkened conditions, this effect is negligible for both colors. But for outside daytime use like construction work or archaeology, red has the advantage.
Cost
Red laser pointers can generally be purchased rather inexpensively, with prices from just a few dollars to around $20 for higher power models capable of projecting a mile or more. Basic low power green laser pointers cost a bit more, typically $15 and up. Higher power green lasers remain relatively expensive.
So from a pure cost perspective, red wins for budget-minded users. But the cost difference is small enough for lower power lasers that it should not be a major factor.
Conclusion
In summary, green laser pointers produce a brighter, more visible dot best suited for use in presentations and indoor settings. They do pose moderately higher eye hazards. Red lasers are more affordable, safer, and work better outdoors and over long distances.
For presentations, green is typically preferred. When using a laser pointer outside during the day, red is recommended. And for stargazing or playing with pets, a moderate power red laser is usually the best choice.
Consider the intended application and environment before choosing between red and green laser pointers. But either can be useful tools when used responsibly.