Videos with transparent backgrounds are often used to create spectacular scenes that are difficult or impossible to shoot live. Color is most often the key parameter for background removal. However, if the foreground object differs in brightness, you can remove the background using this parameter as the key one.
Necessary
- - Adobe After Effects program;
- - video file.
Instructions
Step 1
Open the movie you want to work with in After Effects using the File command, choosing this option in the Import group of the File menu. Move the file with the mouse to the Timeline palette.
Step 2
From the Keying folder in the Effects & Presets palette, take the Luma Key filter and drag it onto the video in the Timeline palette. You can drag it onto the video preview in the Composition palette, after selecting the layer to which you are going to apply the Luma Key.
Step 3
In the Effect Controls palette, adjust the parameters of the applied filter. If you need to remove dark pixels from the video, select the Key Out Darker option from the Key Type list. If, on the contrary, you need to remove highlights, use the Key Out Brighter option.
Step 4
Indicate which pixels you are going to replace with transparent ones by adjusting the Threshold and Tolerance values. The result of changing the settings can be immediately observed in the preview window.
Step 5
Adjust the edges of the opaque area of the image by adjusting the Edge Thin and Edge Feather options. The first parameter will reduce the size of the opaque areas of the video, and the Edge Feather will create an area of semi-transparent pixels at the border of transparent and opaque areas. They are sometimes useful because they soften the hard-cut edges of the foreground shape, and in some cases they can ruin the overall impression of the work by surrounding the cut object with a shimmering halo.
Step 6
If the figure in the foreground is qualitatively separated from the background as a result of previous manipulations, but there are remnants of the background that do not intersect with the object at the edges of the video, you can save the position by removing them with a mask. To do this, select the Pen Tool in the panel located under the main menu. Use it to paint a mask around the area you want to remove from the video.
Step 7
Expand the layer options in the Timeline palette by clicking on the arrow to the left of its name. Expand the mask parameters in the same way, expanding the Mask item. Change the mask mode from Add to Substract by choosing a new mode from the drop-down list.
Step 8
Save the project with the Save Project command from the File menu if you are going to continue working with video in After Effects. If all other processing will be done in another program, save the file with the transparency channel. To do this, send the video to the Render Queue palette using the Add to Render Queue option, which can be found in the Composition menu.
Step 9
In the Render Queue palette, open the video output settings by clicking on the word Lossless. Select RGB + Alpha from the Channels list. After pressing the Render button, the processed clip will start to be saved.
