Chroma Keying and Working with Green Screens > Refining Your Key >

# Adjusting the Front and Matte Luminance Curves

When you create a matte for the front clip, the Modular Keyer automatically creates a matte for the back clip to specify which part of the back clip is used for the composite. By default, the back matte is the inverse of the front matte.

You can adjust the luminance of the front matte and back matte separately in the Matte Curves menu. For example, increase the luminance of the back matte so that more of the back clip shows through at the edges of the key. This creates a better blend at the edges.

To adjust the luminance curves:

1. Click the Result node in the pipeline.

   The Matte Curves menu appears.

   (a) Result box(b) Front matte curve(c) Matte box(d) View box(e) Back matte curve

2. Select Result view from the Result box. This allows you to select a particular image to view as you adjust the curve.
3. From the Result box, select the image you want to view as you adjust the curves.

   Select: | To view:
   --- | ---
   Result | The composite clip.
   Matte | The front matte. You cannot see changes made to the back matte when this view is selected.
   Bmatte | The back matte. You cannot see changes made to the front matte when this view is selected.
   Comp | The composite with a coloured background. The default colour is white. To select a different colour, click the colour swatch below the Edit Mode box. The colour picker appears.

4. To adjust the luminance curve for the front matte, select Front from the Matte box. To adjust the back matte curve, select Back. Alternatively, click a curve to select it.

   (a) 255 (White)(b) Output (remapping of luminance values)(c) 0 (Black)(d) 0 (Black)(e) Input (current luminance values)(f) 255 (White)

   In Move edit mode, click a point to display its tangent handle and drag the handle to adjust the curve. Use other modes in the Edit Mode box (Add, Delete, or Break, for example) to further adjust the curve, adding or deleting points, or breaking tangent handles as needed.