Transparent exports

A transparent canvas lets you export a title, a lower third or an overlay that sits on top of something else. Only four formats keep the transparency, so the format is the choice that matters.

Where: Document tab ▸ Appearance ▸ BackgroundExport sheet ▸ Format
Agent tools: set_canvasexport

Export with transparency

Make the canvas background transparent in the Document tab.
Open the export sheet and pick a format that keeps transparency. The sheet’s footnote ends in alpha, for example VP9 · WEBM · alpha.
Choose Export… or Add to Queue.

Which formats keep transparency

A transparent canvas stays transparent in four formats:

ProRes 4444 (MOV)
HEVC with Alpha (MOV)
VP9 with Alpha (WebM)
Animated PNG

Every other movie format flattens the picture onto black. Animated GIF isn’t one of the four either: a GIF can show a pixel as fully transparent, but it has no alpha channel, so nothing partly transparent survives it.

For a single frame, Save Frame keeps transparency in PNG and HEIC, and JPEG flattens onto black.

The Transparency note

While the canvas background isn’t fully opaque, the Appearance section of the Document tab says how many formats will keep it: “Transparent — kept by 4 export formats.”

If only one or two formats could keep it, the note names them instead of counting. A document with no length can read “Transparent — needs an alpha format.”

Which transparent movie to send

Send	For	Good to know
VP9 with Alpha (WebM)	The web, in a page’s `<video>` in Chrome and Firefox	Whether Safari shows its transparency hasn’t been confirmed, so send Safari HEVC with Alpha.
HEVC with Alpha (MOV)	Safari, QuickTime and Apple’s apps	The delivery file: lossy, 8-bit and smaller than ProRes 4444.
ProRes 4444 (MOV)	Another editor	The master.

VP9 with Alpha shows its transparency only in a player that decodes VP9 with the libvpx decoder. Others, ffmpeg’s default decoder among them, show the picture opaque.

To bring a transparent clip back into Frame Job, export ProRes 4444 or HEVC with Alpha. A VP9 with Alpha file keeps its picture when you import it but loses its transparency, showing black where it was transparent.

Straight alpha

The colour in all three transparent movies is straight, not multiplied by the transparency, so a re-imported ProRes 4444 or HEVC with Alpha file composites to the right colour. If another app asks how a file’s transparency is stored, choose straight.

Frame Job also fills the transparent pixels around the picture, up to 4 pixels out, with the colour of the edge beside them. Without that, a codec that averages colour across pixels would darken the edge. This is automatic, and there’s nothing to set.

The same-shape rule

ProRes 4444, HEVC with Alpha and VP9 with Alpha won’t write a frame of a different shape from the canvas. Fitting the picture into another shape would pad it, and the padding destroys the alpha channel.

Every row in the Size: popup has the canvas’s shape, so this only happens with a Custom… size. Scaling is fine, larger or smaller, as long as the proportions hold, and a size within a pixel of the canvas’s shape is written.

With such a size, the readout names both sizes in place of the usual line, and Export… and Add to Queue grey out: “An export that keeps transparency has to have the canvas’s own shape. This canvas is 1920 × 1080 and 1000 × 1000 is a different shape, so the picture would be padded and the padding loses the alpha channel. Export at 1920 × 1080, at one of the sizes in the popup, or at any size with the same proportions.” If you click Export… with the size still being typed, Frame Job beeps and the readout shows the same sentence.

Good to know

HEVC with Alpha, VP9 with Alpha and Animated PNG are 8-bit. In an HDR project they write the SDR version, so use ProRes 4444 to keep both HDR and transparency.