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Techniques for Adjusting Softness

This section includes three additional methods for adjusting the softness of the key.

Scaling the Softness Ellipsoid to Remove Grey Areas

Increasing the softness may create unwanted grey areas in the foreground subject. There are several ways to remove these grey areas. One method is to plot a pixel in a grey area, then translate, scale, or rotate the softness ellipsoid such that the plotted region is no longer in the ellipsoid. In effect, you will no longer be softening the plotted region.

If you translate, rotate, or proportionally scale the softness ellipsoid, all areas of the ellipsoid are affected to a degree. By contrast, when you use vertex scaling, you can affect a more localized area of the ellipsoid, leaving the rest of the ellipsoid unchanged. Vertex scaling is therefore often the most accurate method to use.

To scale the softness ellipsoid:

1. Show the canvas (press C) and hide the histogram (press H).
2. Use the Soft Display box to change the display of the softness ellipsoid to Cloud.
3. Select the softness ellipsoid in the RGB viewer by clicking on it or selecting Softness from the Picking box.
4. Display the CurResult clip to see the matte.
5. Zoom in to see the grey pixels up close.
6. Click Pref.
7. In the Preferences menu, click Plot.
8. Plot a grey pixel in the foreground subject by clicking it.

   The colour value of the pixel you clicked is plotted in the RGB viewer. The softness ellipsoid arrow passes through the plotted point.

9. To view the exact location of the plotted colour value in relation to the softness ellipsoid, rotate and scale the viewer.

   The plotted point inside the softened region is represented by the softness ellipsoid.

10. Press V, click in the viewer and drag the cursor to the left to scale the ellipsoid down along the axis of the arrow. Watch the image update interactively. As soon as the grey area in the subject disappears, release the cursor to stop scaling the ellipsoid.
    NoteIf you are not satisfied with the result, click Undo to return the ellipsoid to its previous shape, then scale again.
11. If some grey areas remain, plot those areas and repeat the procedure.

Scaling the Softness Ellipsoid to Add to Softness

You can also use the technique described in the previous section to increase the softness at the edges of the key. Start by identifying the region where you want to introduce more softness, and then plot a pixel in that area. You see the colour value in the viewer. Press the V hotkey, then either enlarge or decrease the size of the softness ellipsoid minimally by dragging the cursor to the right or left. Include the colours you want and exclude the rest.

TipDisplay the 3D histogram to help you figure out the direction in which you want to scale the tolerance or softness.

Using the Softness X, Y, and Z Fields

You can also adjust the softness in the key by changing the values in the Softness Scaling X, Y and Z fields. Drag the cursor over the fields, watching the result in the image window. You can often get a good result just by experimenting.

NoteThe Sampling box does not have to be set to Softness to use these fields.