Either type of reticle can be illuminated for use in low light. Illumination is usually provided by a battery powered LED, though a radioactive element containing Tritium may be used for autonomous illumination for approximately 11 years without using a battery, via radioactive decay, like in the British SUSAT sight for the SA80 (L85) assault rifle, or the American ACOG (Advanced Combat Optical Gunsight). The light is projected forward through the scope, and reflects off the back surface of the reticle. Red is the most common color used, as it is the least destructive to the shooter's night vision, but some products use green or yellow dots, either as a single colour or changeable via user selection.

Image quality is in a rifle scope , binocular or Cameras alike.  It is crucial that the optical system of a riflescope deliver as much light as possible to the eye of the shooter. The brighter the image, the sharper the resolution, and the clearer the shot. When selecting your scope, consider brightness, clarity, resolution, power and field-of-view.