Semi-transparent color problem in Prores export

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#1

Have you searched the Docs and Knowledge base? Yes.
Principle Version: 5.14
macOS Version: 11.1
Sketch Version: N/A
Description of what you need help with:

How to export transparent videos from Principle to be used in Final Cut Pro. There appears to be a bug in the export, so that semi-transparent pixels are darker in the export than they were in the Principle document.

Steps to reproduce the behavior:

  1. Create a principle document with some semi-transparent elements e.g. rects with fill (255, 255, 255, 0.5)
  2. Set the artboard fill to transparent
  3. Make a short recording
  4. Save as Prores
  5. Check the colors in output

Screenshots/Sketch File/Principle file: (if applicable)
example document:

image
image1227×681 87.9 KB

#2

example export:

image
image522×555 41.4 KB

Note that the white squares become grey. The black seems unaffected.

#3

The same problem can be seen when importing the prores file into Final Cut, which is the workflow I’m trying to use.

image
image1392×1022 212 KB

I wonder if it was a problem with alpha premultiplication during the export?

You can also see this bug as black fringing around anti-aliased graphics when doing a transparent export.

I’ll attach the principle document I’m using, and the prores file I exported.

Transparency bug.mov

By the way, thank you so much for Principle! It’s a really great bit of software, I absolutely love using it :slight_smile:

#4

I’ll look into this. alpha premultiplication does seem like a possibility.

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