What it does
Leaves a decaying trail of recent frames behind moving content.
The look is older than video. Étienne-Jules Marey was photographing multiple exposures of birds and fencers onto single plates in the 1880s to study movement, and Harold Edgerton flashed strobes at drops of milk and golf swings to freeze a whole motion into one image. Those chronophotographs are exactly what an echo effect produces: a subject accompanied by its own recent past, arranged in time order, fading as it recedes.
Digitally the trail is built from a buffer of stored frames. The effect reaches back into that history at even intervals and layers the older frames under the live one, each dimmed a little more than the last, so the trail decays smoothly toward nothing. How far apart the taps sit changes the character entirely: pulled close together the ghosts fuse into a continuous smear, a comet tail; spread apart they separate into distinct stuttering copies, the strobe look. The echoes are combined by taking the brightest value at each pixel rather than adding, which is why highlights streak gloriously without the whole frame blowing out to white.
Because it reads the recent past, the effect only exists in motion. On a static shot every stored frame is identical and the echo disappears into the image; play a moving subject and the trail condenses behind it like breath on glass. It also trails everything beneath it in the stack, so type sliding across the frame, a bouncing composition, or plain footage all grow tails, and the trail accumulates as the video plays, settling into itself over the first fraction of a second.
Signature looks
Comet tail
Echoes packed tightly so they fuse into a continuous smear behind the subject. Motion reads as a streak of itself, liquid and fast.
Strobe trail
Widely spaced echoes that stay separate: a chain of distinct frozen copies trailing the movement, the chronophotography look on live footage.
Light writing
A bright subject on a dark scene with a long, slow decay. Highlights persist and drag, so anything luminous writes itself across the frame.
Try it on your own footage
This effect runs live in the Modulate editor, with layers, effect chains, masks, and keyframes. Free, no signup, nothing to install.
Common questions
What is a motion trail effect?
An effect that follows moving subjects with fading copies of their recent positions. Each copy is an actual earlier frame of the video, dimmed according to its age, so the trail records where things really were rather than smearing where they might have been. It is also called an echo effect, after the After Effects operator that popularized the technique.
What is the difference between a motion trail and motion blur?
Motion blur smears each frame along its direction of movement, simulating what a camera shutter sees during a single exposure. A motion trail composites multiple whole frames from different moments, so the subject stays sharp and is followed by sharp ghosts of itself. Blur is about one instant stretched; a trail is about many instants stacked.
Why don’t the trails blow out to white?
Because the echoes are combined by taking the maximum of each channel rather than adding them. Addition piles brightness on brightness, so a few overlapping echoes of anything light saturate instantly. Taking the brightest value lets highlights streak and persist while everything stays within range, which is the standard trick for luminous trails.
Why does the echo effect need the video to play?
The trail is made of genuinely remembered frames, so a history has to accumulate before there is anything to show. On a paused or static image every remembered frame matches the current one and the effect is invisible. Press play and the buffer fills within a fraction of a second, and the trail condenses behind whatever moves.
How do I add a motion trail to a video?
In Modulate, add the Echo effect to your composition and press play: it keeps a rolling history of frames on the GPU and composites the trail live in the browser. The number of echoes, how far apart in time they sit, and how fast they fade are all adjustable while the footage runs, and the effect trails every layer beneath it, including moving text.
Related effects
Slit-scan effect
Each pixel shows a different moment in time — a gradient or control map melts the image across recent frames for slit-scan, rolling-shutter, and time-displacement looks.
Datamoshing
Smears moving parts of the image into blocky trails, like a corrupted video that never gets a clean frame.