Using Field Mode

Video clips with fast-moving objects can contain artifacts characterized by edge misalignments. These artifacts occur when the odd and even fields are combined into frames. Applying Erode, Blur, or Shrink effects to images containing misalignments does not produce good results. To solve this problem, use Field mode. In Field mode, frames are separated into fields and the effects are applied to the individual fields. The fields are then recombined into frames. This is all done “behind the scenes”—that is, fields are not displayed in the image window.

There are four matte controls in the Edge menu you can use to enhance the edges of the key—Edges, Shrink, Erode, and Blur.

These controls are processed sequentially: Edges is processed first, then Shrink, Erode, and lastly, Blur.

To transform an image into edges:

1. Select CurResult view from the View box.
2. Enable Edges.
3. Set a value for the edge-detection sensitivity in the Width field to the right of the Edge button. This control affects how the edge-detection algorithm determines whether or not each pixel forms part of the edge.
4. Set the Minimum Input Level in the Min field.

   The Minimum Input Level sets the start of the range of luminance values in the image. Pixels with luminance values below the Minimum Input Level are mapped to black (0).

5. Set the Maximum Input Level in the Max field.

   The Maximum Input Level sets the end of the range of luminance values in the image. Pixels with luminance values greater than the Maximum Input Level are mapped to white (255 in 8-bit mode and 4095 in 12-bit mode).

6. Enable Shrink.
7. Set the width of the edge using the Shrink Width field. Enter a negative Shrink value to expand the border, and therefore widen the edge. Enter a positive Shrink value to decrease the width of the edge.

   The edge before adjusting the width using the Shrink Width field

   The edge after adjusting the width using the Shrink Width field

To shrink the edge of the matte:

1. Select CurResult view from the View box.
2. Enable Shrink.
3. Set a value in the Width field next to the Shrink button.

   This value specifies the width of the border, in number of pixels, that is removed from the edge of the matte.

   The matte before applying the Shrink filter

   The matte after applying a shrink width value of 1.00

To erode the edge of the matte:

1. Select CurResult view from the View box.
2. Enable Erode.
3. Set a value in the Erode Width field.

   This value specifies the width of the matte border, in number of pixels, that will be softened.

   The matte before applying the erode filter

   The matte after setting the erode width value to 1.00

To blur the edge of the matte:

1. Select CurResult view from the View box.
2. Enable Blur.
3. If you want the image to be equally blurred horizontally and vertically, click P to enable a proportional blur.
4. Set the width and height of the blur. When P is enabled, enter a value in either field. The higher the number, the greater the blur.

   The matte before applying a blur

   The matte after setting the blur width and heigh values to 1.00