From the course: Premiere Pro Guru: Compositing and Masks (2015)

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Two types of alpha channels: Straight and premultiplied

Two types of alpha channels: Straight and premultiplied - Premiere Pro Tutorial

From the course: Premiere Pro Guru: Compositing and Masks (2015)

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Two types of alpha channels: Straight and premultiplied

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- There are two ways in which the alpha channel information is stored in the file: straight and premultiplied. The alpha channels are exactly the same in both files but the color channels are different depending on which one you use. With a straight alpha channel the transparency information is stored only in the alpha channel, the other channels are left intact. Therefore, no transparency information is displayed unless you're showing the clip in an application that supports this type of alpha channel. However, the premultiplied alpha channels stores the transparency in both the alpha channel and also in the other channels, which are multiplied or mixed with a background color. So if you have semitransparent edges on the clip with the premultiplied alpha those pixels will shift towards the color of the background. Let's try it, open sequence 1.2. Notice the first clip, this is straight alpha. Now, see the second clip. See how it's displaying with a little bit darker pixels on the…

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