Join Steve Wright for an in-depth discussion in this video The classic Premultiply > Merge over, part of VFX Keying: Master Course.
- [Steve] This chapter is about the many different ways you can combine your foreground layer with the background. This is about the compositing, not keying, spill suppression, or color correction, as these are covered in other chapters. This first video is about the classic premult, then merge over workflow. So we can see it right here, we're pushing it a bit. So starting with our green screen, we of course do the obligatory denoise. Now here is a core mat, that has already been prepared. And we use that with the spill suppression, just to dig out the spill suppression in the core.
So this is our spill-suppressed image, and here is our key, which has already been created, because this is not about creating the key, this is about putting all the pieces together. So we take our key, and with the copy node, we put it behind our spill-suppressed images. So now, I have a four channel, not premultiplied image. We do the premult, which clears the outside area to black, and then we do the merge over with the merge over node.
Now I got a little toggle switch tchotchke here, that I made for you, that I can just toggle between the test pattern, and a real comp. Of course, the actual background you use has a dramatic effect on the edge treatment. Well, that was easy, but lets take a closer look at our comp. I'm gonna push in over here. Hmm, I have this unpleasant, dark edge thing going on here. Um, if we look at his hair, I got some pretty good detail. Keep in mind, that this was an unusually nice green screen, okay? But if I compare the original green screen, with the comp, I've lost a little bit of that hair detail.
Let's check over here with the lady. And, we can see we've lost again, a little bit of our hair detail in the comp. Okay? Now, some of the later videos in this chapter are going to address these issues. Well that was easy, but there were issues with the fine edge detail, and motion blur. The next video will show us how to get more control over the edges, by using the admix node for the composite.
Note: This course was created by Steve Wright, author of the seminal book, Digital Compositing for Film and Video. We are proud to host this course in our library.
- Creating an uber key
- Keying green-screen vs. blue-screen footage
- Preprocessing footage
- Building a clean plate
- Making luma keys
- Keying on hue and saturation
- Pasting keys together
- Grain management
- Saving time with garbage mattes
- Using spill suppression
- Improving edges
- Color correcting keys
- Sweetening the comp
- Alternative compositing workflows
- Fixing edge problems
- Using KEYLIGHT, Primatte, Ultimatte, and other tools
Skill Level Intermediate
Photorealistic Lighting with Maya and Nukewith Mark Lefitz2h 24m Intermediate
NUKE Compositing: Sci-Fi Force Fieldwith Steve Wright2h 12m Intermediate
1. Keying Workflows
2. Pre-Processing the Green Screen
3. Other Types of Keys
4. Building the Uber Key
5. Spill Suppression
6. Compositing Techniques
7. Color Correcting
How to match grade two clips4m 15s
8. Workflow Examples
9. Sweetening the Comp
10. Fixing Edge Problems
11. Special Keying Solutions
12. Appendix: Keyer Tutorials
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