After Effects CRT Vector-display Compositing Problem

Question

I am recording a CRT vector display with my Iphone. The display I am recording is a modified game console called a Vectrex. I want to composite multiple frames of the vector drawing to create a temporal accumulation/trail effect. What is the best After Effects workflow for isolating the phosphor signal and combining multiple time-offset copies using Add/Screen while retaining the fine vector lines? Any assistance would be great.

CORCTON34033231 · Accepted Answer

Hi! For this kind of temporal accumulation / trail effect, use Effect > Time > Echo — it's designed exactly for this. Apply it to your footage layer, then in Effect Controls set:

- Echo Time: a small negative value (e.g. -0.033) so it samples previous frames

- Number of Echoes: 5–10 (however many frames you want stacked)

- Decay: around 0.5 for a nice falloff

- Echo Operator: Add or Screen

That stacks the time-offset copies inside a single layer — no manual duplication and shifting of layers needed.

To isolate the phosphor signal: first crush the blacks with Levels or Curves so the background is pure black and only the vector lines remain. Otherwise the Add/Screen stacking will lift the background and wash out the fine lines.

One capture tip: iPhone footage of a CRT can flicker or show banding if the shutter speed doesn't match the display's refresh — locking exposure/shutter speed while recording helps.

Reference (Echo effect settings): https://helpx.adobe.com/after-effects/desktop/apply-effects-and-animation-presets/list-of-effects/time-effects.html

CORCTON34033231 · Answer

Luma Key is the right direction! A few things will clean it up a lot:

1. Contrast first. Luma Key keys purely on luminance, so apply Levels to the footage BEFORE the key: crush the blacks toward pure black and lift the whites a touch. The bigger the luminance gap between the phosphor lines and the background, the cleaner the key (Adobe's own guidance says the key works best when the subject and background have very different luminance).

2. Tune Tolerance, not just Threshold. With Key Type on Key Out Darker, Threshold sets the luminance point the matte pivots on — Tolerance widens the brightness range that gets keyed out. Raise Tolerance gradually until the background drops, then add a little Edge Feather (1–2) to smooth the edges.

3. Consider Unmult instead. Since your background is black, the Unmult effect is built exactly for this — it keys out the black background by brightness while keeping the bright phosphor lines intact (it even has a Remove Color Matting option). It often gives a better result than Luma Key for glowing graphics on black.

Keep the order: key first, then apply Echo on the isolated layer. And 1/30 at 30 fps is a 360° shutter angle — maximum light on the sensor, which is exactly what you want here, so your camera settings look right.

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