Now that you know what an alpha channel is, you probably realized that you've been making adjustments to the opacity of pixels using this channel for ages. There are automatic ways of doing this too, and two of the most common are chroma key and luma key. These two approaches to adjusting alpha channels are so well-established, they've become a staple in production and post production for films and TV. Learn the principles behind these powerful compositing tools in this video.
- [Instructor] The alpha channel for a pixel…uses the same bit depth as the color channels.…The numbers are the same,…so it's fairly straightforward…to translate one channel figure into another.…You can designate areas that should be transparent…manually using a mask,…and when you do that…you're using a shape to set an adjustment…to just the alpha channel on the pixels selected.…But you can also automatically apply adjustments…to the alpha channel on pixels…based on colors or luminance.…Let's look at a simple example of this, lumakey.…
Put simply, when you lumakey pixels,…you convert the luminance level of each pixel…to its alpha channel.…Unless you make any adjustments to the effects settings,…only pixels that are perfectly black…will be completely transparent,…because only an alpha channel of zero…is totally invisible.…The brighter each pixel is, the more opaque it will be,…until pixels are completely white…and therefore completely opaque.…Lumakey can produce some lovely effects,…if they're planned for.…You'll normally specify a minimum luminance,…
Get ready to remove the mystery behind terms you've encountered. If you work in a creative profession, this can enhance your command of the tools you use. Learn what a pixel really is, what color channels are, and what audio frequency is. Discover how color channels, bit depth, and video frame rates work. Find out the difference between codecs and file formats, and how compression is involved. By the end of this course, you'll know how to answer common client questions—like, whether a logo should be supplied in vector or bitmap form, and more.
Note: Motion graphics in this course were provided by Chelsea Parrish: chelseaparrish.com.
- What is a pixel?
- Aspect ratios
- Bit depth
- Alpha and transparency
- Light and color channels
- Color modes: RGB, YUV, CMYK
- Camera depth of field
- Chroma Key and Luma Key
- Blend modes
- Color wheels, vectorscopes, and waveforms
- Video compression and codecs
- Frame rates and timecode
- File formats
- Audio amplitude
- Capturing audio tone as frequency
- Audio timing using the phase
Skill Level Beginner
Learning Video Production and Editingwith Rob Garrott19m 25s Beginner
Video Foundations: Cameras and Shootingwith Anthony Q. Artis2h 58m Appropriate for all
Introduction to Video Dialogue Editingwith Ashley Kennedy3h 14m Appropriate for all
1. How Do Computers Think?
2. How Cameras and Computers Think about Color
3. The Language of Color
4. The Shape of Your Picture and the Speed of Your Video
5. Storing Everything (Codecs)
6. Color Wheels, Vectorscopes, and Waveforms
Understanding waveforms2m 39s
7. Making Changes
8. Audio Made Simple
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