With apologies to Dr. Seuss, can we have a conversation about the differences between red dot and green dot optics? Why do some optics offer both? Do I want an MOA dot or ring, what size should they be, and why doesn’t anyone make blue or purple dot optics?
Why are there red and green optics?
Without turning this into an anatomy lesson, your eye has two types of vision receptors. rods and cones, so-named because of their shape. Rods support low-light vision, while cones support color. Rods only function in low light through a chemical called rhodopsin, which is bleached by light and takes around 30 minutes to regenerate.
Rhodopsin is much less sensitive to the color red, which is why, along with the fact that early photographic film wasn’t sensitive to red light, red traditionally was used to maintain night vision.
However, the color that has the least effect on night vision is not the same thing as the color that will let you see at the lowest possible level of illumination, and it turns out that our eyes are more sensitive to green light. In fact, if you look at two dots of light at the same power level, the green dot will appear to be 30 times as bright as the red light. This means that lower power levels can be used for green, saving battery power.
Green lasers still are up to 32 times more expensive than red lasers, limiting them to higher-end scopes.
We are all different
Individuals’ visual acuity at low light levels varies quite a bit, so what is perfect for one might be too bright or too dim for another. Laser diodes also have minimum and maximum brightness levels. Based on these two facts, it is possible that the minimum level of a green optic at night or the maximum level of a red optic during the day might not be appropriate for the work at hand.
If you also are working with night vision, it may be jarring to move back and forth between a green device and a red dot. Why are night-vision screens green? Device makers experimented with a few different colors and found that the different shades that make up a night vision image are most accurately perceived and distinguished when they’re green – and the lower levels we can perceive saves battery power.
There is also the question of background. Green dots might get lost in the forest while red dots might get lost in a sea of taillights and light bars. Some scopes can switch between red and green illumination. What you choose depends on your budget and where you expect it to be used most often.
Today’s math lesson
Just like a minute is 1/60 of an hour, a minute of angle, or MOA, is 1/60 of a degree. More important, 1 MOA spreads about 1 inch per 100 yards.
MOA makes shooting calculations simple because you can divide the distance in yards you are shooting by 100 and you will know how big 1 MOA is in inches. This article covers everything you need to know about how to use MOA when aiming.
Scopes come with myriad reticles such as dot, circle, minute of angle markers and so on. A too-big dot may cover your target while a ring may be harder to center. The type and color of your reticle come down to the scope’s mission and the skills of the cop using it. MOA markers are only useful if the shooter knows how to use them, otherwise they just clutter up the image.