Settings and Macros/SpillMerge Description

The following inputs appear on the tool's tile in the Flow Editor:

Input

Source image to be despilled. Required.

Background

Background image to be merged into the foreground's screen and spill area. Optional.

The controls are arranged in a convenient order of operations. Above all control tabs is the Output Mode multi-button. By default it is set to the final output so you have immediate feedback. For fine-tuning the controls, however, it's suggested to toggle them from left to right. Start with the despilled intermediate result so you can tweak the despilling tab. Then tweak the spill matte and finally the merged result using the third tab.

These controls are concealed by default since they are an optional process. It is necessary for plates like film scans which exhibit a green color cast that mustn't be confused with green spill.

If your plate has a noticeable color cast, SpillMerge can neutralize the input image before applying its despill formula. This will often produce better results and is highly recommended when the plate has an overall color cast that would otherwise be mistaken for green spill. For example, if your green screen was shot on traditional film and your plate is greenish due to the scanning process and printer lights settings, SpillMerge would subtract green from every pixel, even from the actors' faces which aren't affected by spill at all. This will make them look purple.

The neutralization process is a simple primary grade, where the red, green and blue channels are multiplied by correction factors. This process is perfectly invertible and it should be reverted after despilling. Disable this checkbox if you want to continue to work on the neutralized plate. You can also remove white balance issues this way.

Pick a color that should be neutral (i.e. white or gray) but isn't due to the plate's overall color cast. Suitable spots for color picking are white shirts or walls that point away from the green screen. Take care to not pick a spot that is actually affected by actual bounce light from the green or blue screen. This will be dealt with by the despill formula. As with every color picker, you need to pick from the image upstream of this tool. However, you can also disable the Neutralize Before Despill checkbox to safely pick from the output of this macro.

Duh.

Select the despilling formula. The options will be familiar to you from Fusion's keying tools. "Medium" has been omitted since it usually produces visible edges in the despilled result.

The fine-tuning slider allows you to tweak the despill formula by changing the ratio of channels that are mixed (red & blue for green screens and red & green for blue screens). This allows you to tackle difficult fringe problems as demonstrated in this example:

Using this slider you can restore the despilled area to the luminance of the original green or blue screen. This is often useful to prevent dark fringes when pulling a traditional key. When adding a background using SpillMerge, it's often not necessary and can sometimes make integrating an image more difficult.

Here you can reveal a color wheel as known from Fusion's Color Corrector tool. After the despill formula, the area where the screen used to be might still exhibit a brownish or purple tint. Using the color wheel you can completely desaturate the area or tint it appropriately for the background that should be inserted. Remember, if you use SpillMerge to merge a background image, the spill area will be affected by that image anyways. The color wheel is best used as a last step to tweak the integration of foreground and background.

The controls of this tab are familiar from Fusion's Matte Control tool. You can tweak the spill matte - the difference between the original plate and the despilled result - which is subsequently used to add the background image and tint the spill area.

This tab controls the color correction that is applied to the background image before it gets merges into the foreground image.

By default, the background is added to the foreground in a logarithmic color space (making it a multiplication in linear terms). This is usually a better solution to prevent harsh blacks due to clipping.

This label reveals gain, lift and contrast sliders known from the BrightnessContrast tool. The reason they are hidden is that the main adjustment should be performed via the low/high thresholds below first before using these.

Desaturates the Background image to keep more of the tint that is present in the spill area (or has been set using the tint color wheel on the first tab).

Use this range control to adjust the background's contrast until the result is to your liking. The way SpillMerge works is by using the spill matte to combine foreground and background images in an additiv process. This means that by default the result will look desaturated. The best workflow is to put the background into the viewer's B buffer to toggle back and forth while adjusting the sliders on this tab until the merged result looks similar to the raw background. It never will match completely since reflections and light variations will always affect the merged result. But this is of course a feature of SpillMerge since this macro is meant to preserve finest details or reflections on glass.

The aim of SpillMerge is to crank up the background's contrast until it has negative as well as superbright values. So clipping at 0 or 1 before the merge happens - which is what these options will do - will rarely provide a benefit. The checkboxes are here just to complete the Brightness/Contrast controls.