Tracers from DOI

Tracers are the experience of trails of varying length and opacity being left behind moving objects in the visual field, producing an effect similar to long-exposure photography. When an object moves across one's field of vision, a series of translucent afterimages persist along the path of motion, creating a smooth trail that lingers briefly before fading. These trails can manifest in the same color as the moving object or occasionally appear in a randomly selected color of their own.

A reliable way to observe this effect is to move one's hand slowly in front of one's face or toss a small object while under the influence of a psychedelic compound. The trailing afterimages will be clearly visible, stretching behind the moving object like a comet's tail. The length, opacity, and persistence of these trails vary significantly depending on the intensity of the effect and the speed of the moving object.

At the lowest intensity, tracers appear as nearly transparent afterimages that fade quickly and drag closely behind moving objects. They are most visible against high-contrast backgrounds and may be mistaken for ordinary persistence of vision. As the effect intensifies, the trails become more opaque, longer, and more persistent, with multiple distinct afterimages stacking up along the path of motion. Colors within the trails may become vivid and saturated.

At moderate levels, tracers become a dominant feature of visual perception, with every moving object in the visual field producing clearly visible trails. Eye movements themselves may begin to produce trailing effects, causing the entire visual scene to smear briefly when the gaze shifts. This can make reading and tracking moving objects noticeably more difficult.

At peak intensity, the visual field becomes so sensitive to tracer formation that even the slightest movement of objects or the eyes produces all-encompassing smearing and blurring. Vision may become extremely difficult unless one's eyes are kept completely still in a motionless environment, as trails linger almost indefinitely and overlap into a continuous blur. This level is relatively rare and typically requires high doses.

Tracers are most commonly induced under the influence of mild to moderate dosages of psychedelic compounds such as LSD, psilocybin, mescaline, and 2C-B. They can also occur with MDMA, cannabis, and certain dissociatives. The effect is often accompanied by drifting, after images, and visual acuity enhancement, and is one of the most universally recognized and reported psychedelic visual effects.