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Video Codecs / Image Sequences With Alpha Channels!

Video Codecs / Image Sequences With Alpha Channels!

Video Codecs / Image Sequences With Alpha Channels! - Motionmile Blog

The technology behind video and graphics can become confusing and difficult to keep track of, and alpha channels are a key example of this. To properly edit and create beautiful videos and image sequences it is essential to get to grips with what alpha channels are and how they work. Alpha channels can be used to make some really awesome effects in your videos and are definitely a skill to learn if you want to master video editing and image sequencing.


What Is An Alpha Channel?

In general, a video will have three channels of information: red, green, and blue. An alpha channel is an additional channel that defines different areas of transparency within the image or clip. If you import a movie or a still image from an application that supports alpha channels, it may have an alpha channel in addition to its three colour channels. An alpha channel is a greyscale channel where levels of white and black determine the varying degrees of transparency that are applied to the colour channels during compositing.

When you import a movie or image file, if it has an alpha channel it will be recognised immediately. When you edit the movie or image file into a sequence, video editing software such as Adobe After Effects will use the existing alpha channel to composite the movie or image sequence.


Learning Alpha Channels in Adobe After Effects

Mastering alpha channels can really bring your videos and image sequences to life, so learning how to use them effectively can be hugely beneficial. These After Effects tutorials cover various aspects of using alpha channels in title sequences and videos:

Rendering With Alpha Channels

This quick tutorial covers the basics on how to render a finished project in After Effects. This is full of useful tips on a few different formats and codecs and the different results you can achieve with each. You will also learn how to render an image sequence and how to render with alpha channel backgrounds. This tutorial also covers how to create your own render presets with alpha channels, which will save huge amounts of time on future projects.

Flat Typography Titles Using Alpha Channels

This After Effects typography tutorial teaches you how to create a set of 3 different typography styled titles and how alpha channels can create unique typography effects. You will learn how to add a stroke to title text, which is great for increasing the thickness of lighter fonts. You’ll also learn to add some animators for the scale and position, and how to use a few default after effects plugins to add subtly animated shadows to the text. This After Effects tutorial will also cover how to use an alpha inverted matte to change a title sequences appearance.

Create Metallic Text With Alpha Channels

This brief tutorial teaches you how to create 3D metallic text in After Effects, without the use for any third party plugins or additional software. You will learn a quick method to create 3D bevelled edges and animated metallic reflections using alpha channels. This simple tutorial will equip you with a range of skills that can be utilised across a range of different title sequences, videos or image sequences that you might be working on.


How To Export Alpha Channels

If you are creating an overlay or title sequence and you want to make sure the alpha channel is also exported, you need to use the correct video codecs and image sequences. Using the right codecs for alpha channels will make layering your clips effortless and simple. Exporting to a QuickTime format will give you a few codec options with alpha channels. One of the most popular and versatile codecs is GoPro Cineform which is found under the QuickTime format. If you would rather use an Apple codec, the ProRes codec is a useful alternative, or you can also use the Animation codec.

If you have no need for video files, you can use image formats with alpha channels which can be easily used to create sequences. If you are importing images in After Effects, it is often easier and more practical to select just the first image with image sequencing enable as opposed to select all of the images individually. Popular image formats such as PNG and TIFF will use alpha channels, whilst television broadcasters often use Cineon and DPX files, and VFX houses prefer codecs such as Maya IFF.

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