Tutorial for Primatte Keyer 5.1

This tutorial goes over the basics of using Primatte. We are using a well-lit bluescreen; there is a lot of fine hair detail that would be lost when keying with other keying methods; and there is a noticeable amount of blue spill on her clothing, skin, and hair. Let's get started!

The following steps will guide you through pulling the initial key, after which we will suppress the blue spill in the foreground. The initial step is always to highlight the foreground layer in your Timeline and apply Primatte.

Step 1

There are two ways to initially pull a key in Primatte. One option is to press the Auto Compute button, which is located in the Keying group. The Auto Compute button will automatically eliminate the background color and clean up any foreground noise using our new Primatte 5.1 algorithm. If Auto Compute does its job, then you may be able to skip to Step 4 of this tutorial.

The second option is to manually select the background using the Select BG tool, found under the Keying> Selection> Select group. After choosing this tool, go to the Sampling Style menu and choose Rectangle. Sample a large area of the bluescreen. In most host applications, this means sampling in the Canvas, Composition, Project or other Preview window. In Final Cut Pro, you sample in the Filter Controls window.

Make sure that you do not include any of your model’s hair or other internal details. Primatte will take the value of each pixel in the sample range and make any pixels in that range transparent. As soon as the sample is made Primatte pulls a key and the foreground appears composited over the background.

The new Adjust Light On/Off feature can be used before or after pulling the initial key with either tool. This checkbox is also in the Keying group, and cleans up additional background noise when turned on.

Step 2

Go to the Keying> View pop-up. Chose the Matte option to view the alpha channel being generated by Primatte. In our example, there is quite a bit of white noise in the background, especially in the corners of the image.

To remove this noise, change the Sampling Style back to Point. Select the Clean BG tool and drag a line down the noisy right side of the image. Primatte samples away almost all the noise. Repeat this sampling operation as many times as needed to remove all the noise from the background.

Don’t try to sample too much of the image at once. It should take you three to five samples to remove all the noise. Be careful of the fine wispy hair detail protruding from Alex’s head. If you happen to accidentally select this hair detail while sampling the background the hair will be keyed out, significantly reducing the quality of the matte.

In our example below, the background areas of our matte are quite clean and without much noise. You may occasionally need to pull a matte with fine detail in a very noisy setting. If this is the case, leave a little noise around the fine detail, since this can be cleaned up later using the Fine Tune tool in the Selection> Select group.

Step 3

The next step is to sample away any grayish areas in the foreground. Click the Clean FG button, and sample any areas inside the foreground that are not completely white. As you did with the background, make as many samples as necessary to get the foreground completely white.

If your foreground subject contains colors that are close to your backing screen, you may want to turn on the Hybrid checkbox found in the Keying> Refinement> Advanced group. Turning on Hybrid creates an inner matte that will help fill any transparencies within the body of your matte.

To clean the edges of your matte, increase the Hybrid Blur and Hybrid Erode sliders. This will shrink and blur the matte inward. To see how this tool is working, change your View mode to Hybrid Matte while adjusting the sliders.

Step 4

Now that we have a good matte, let's use Primatte’s spill suppression tools to clean up areas of blue tint in the foreground. Go back to the View pop-up and set it to Comp mode. If you look at our model's face, you notice a light blue tint. There is also a light blue tint on her arm. Much like we did with the matte, we will sample these areas away.

Step 5

In the Correction group, lets choose the Spill Sponge and sample the blue areas on the side of the model's arm. Below left, the spill area is sampled. Below right, the result of the sample.

The blue is removed from all similar color regions over the entire image, such as the left side of her arm, not just in the area that we sampled. When you sample an area, Primatte calculates the color to be removed and applies that calculation to the entire image. Similar to sampling the foreground and background colors, spill suppression often requires more than one sample.

Occasionally a sample range of only one pixel, accomplished by one mouse click, can remove subtle spill areas. Below left to right, clicking once in the blue spill area on the red shirt yields excellent results.

Below left to right, if there is still some blue spill on the subject, simply click to sample it away. If you find that you remove too much spill, undo your spill operation and sample a smaller area.

When sampling to suppress spill, it is a good idea to sample both light and dark areas to make sure you get all possible color tones. For example, to remove all the spill from our model, the samples should incorporate light and dark flesh areas, light and dark clothing areas, and (if needed) light and dark hair samples.

Step 6

Almost all of the keying and spill suppression in Primatte is performed through sampling the image, but occasionally you will want to manually fine tune the key for best results. A likely situation is if you remove too much spill during a spill suppression operation.

If you sample too much spill color, the image will take on a tint. The color of this tint depends on the original key color. Generally, for blue screens the tint will be yellow and for green screens it will be magenta.

In the example below, by using the Spill Sponge we over-sample spill from the subject's hair. This gives us a bright yellow color on the hair edge. We want to dial back the amount of spill suppression to give this edge a more natural color.

Click the Fine Tune tool to activate its sliders. Sample the yellow edge of the hair area. Once you have completed the sample the Fine Tuning sliders will snap the current Spill, Transparency, and Detail values of the sampled pixels.

Step 7

To decrease the amount of spill suppression, move the Spill slider to the left. This reduces the amount of suppression and puts back some of the blue that was originally removed.

It doesn't take a lot of adjustment to get to the right amount of spill suppression. In our example below, we went from a value of 0.44 to 0.39. This slight adjustment gives the hair a far more natural look. To adjust the Transparency or Detail values, you would follow exactly the same sampling process.

Step 8

In the previous steps, we created a good matte and easily removed the blue spill from the foreground. In terms of getting a complete composite, however, this is just the first step.

Below left, the keyed, spill-corrected foreground. Unless the project calls for your foreground to be composited over a black background, you will need to color correct it so it integrates with the composite environment.

Consider the composited image, below right. Even though we have removed the blue spill, the colors in our model remain largely unchanged. The composite environment, however, is comprised of greens and browns. Imagine if the model was actually standing on this grassy area. The light from the sun would hit the grass, and green light would bounce up and off her body, giving it a slight green tint. Skip the color correction filters because Primatte Keyer gives you a couple of excellent tools to mimic this type of environmental lighting.

There is really no 'correct' procedure when deciding whether an element needs color correction and how to do this. The following steps may not be the ones that you would choose, and are included here simply to provide an overview of the Primatte tools.

Step 9

In the Composite Controls group, open the Composite Matcher group. Click the Enable checkbox to turn on Color Matcher.

The Background Layer pop-up designates which layer is used to color the foreground. This can be a single background layer or a pre-comped After Effects composite with many layers. For our example, we are using the grassy photograph as our Background Layer choice. You will see an immediate change as Primatte samples the tonal range of the background and remaps the foreground colors accordingly. Below left to right, the composite changes to a more subtle coloration.

Step 10

Let's adjust the automatic Color Matcher remap. The easiest way is to adjust the Strength slider. By default, Strength is set to 50%. A value of 0 means no colors in the foreground are remapped, and a value of 100 means that all of the colors are remapped.

Start by reducing the amount of the automatic correction from 50% to 25%. This restores a more natural flesh tone to the skin while retaining some of the bounced light qualities of the composite. Below left to right, before and after the Strength correction.

Step 11

Our next step is to fine tune the individual aspects of the remapping process. To do so, Color Matcher has three sets of RGB sliders which individually color correct the Highlight, Midtone, and Shadow areas of the image.

Below left, the highlight areas of the blonde hair at top right have become a little too green. Expand the Highlight sliders and set the Green value to -30. This will knock out some of the green tint and leave with a more natural hair color, shown below right. Primatte gives you a great deal of color correction control with these RGB sliders so you can color correct the foreground as desired.

Step 12

We looked at how Color Matcher can color correct a foreground to match the background. But what if the composite environment contains extreme lighting? Let’s take a look at another example. This composite has been pre-keyed and color corrected, and shows the our model in front a sunset background with extreme colors and backlighting.

While the foreground colors match the composite environment, the edges don’t contain the appropriate amount of backlighting. When an object stands in front of a bright light, the strength of the light causes bleed around the edges of the foreground. To simulate this effect, we will use Light Wrap.

Step 13

In the Composite Controls group, open the Light Wrap group. Click the Enable checkbox to turn on Light Wrap. Unlike Color Matcher, there is no immediate change because we have not yet chosen a composite mode for the Light Wrap effect.

From the Comp Mode pop-up, choose Add. The edges of the foreground will immediately appear to have light from the background wrapping around them. The most common mode you will use is Add. Screen is often a good mode to use to cover up bad edges on your foreground element. With a little experimentation, you will soon learn which modes work best for common compositing situations.

Below left, the wrap effect needs to be thicker and more pronounced to better represent the amount of light given off by the blazing sun in the background, and for this we have the Width value. The default width is 4. Below right, increase Width to 25 and you will see a difference. In this example, a higher Wrap value contributes significantly to the believability of the shot.

Conclusion

In this tutorial, we have covered the basics of pulling a key, then color correcting the foreground to match the background. If you look at our before and after images, the effect is quite remarkable.