After Effects CRT Vector-display Compositing Problem

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.

Chatgpt told me to use Luma Key in After Effects to isolate the highlights on the screen of the Vectrex. The setting on the Luma Key effect is “Key Out Darker”. The result I have obtained from this is not ideal, but in the right direction. I am using the Iphone app Blackmagic Camera App for recording the graphics on the Vectrex. On this app my frames per second is 30, shutter speed is 1/30, ISO is 100 and white balance is 4300K. Can someone advise me further?

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