When you want to improve contrast by modifying both the chroma and luma content simultaneously without changing the black and white points, use the Gamma controls. You only need to make small adjustments to the RGB gamma curves to improve the contrast.

You can adjust the RGB gamma curves uniformly using the RGB Gamma fields.

You can also use a second set of adjustment curves to tweak each colour channel, as well as the luminance channel, regionally.

After making uniform or regional adjustments, if you are not satisfied with the result, you can reset each channel's gamma or adjustment curve, or clear edited curve values for individual frames.

To improve contrast using gamma:

1. Click Basics to display the Basics menu.
2. Select Gamma from the Trackball option box.
3. Display the gamma curve(s) you want to adjust.

   Enable:	To display:
   RGB	The R, G, and B gamma curves at the same time.
   Red, Green, or Blue	The R, G, or B gamma curve individually.
   Luminance	The Luminance curve. Use this curve to modify luminance levels locally without affecting the overall luminance.

   Two curves are displayed for each channel, the original gamma curve, and an adjustment curve with control points for regional control. Initially these curves overlap.

   
   

   (a) Red channel's gamma curve  (b) Red channel's adjustment curve  (c) Added control points on adjustment curve  

4. While monitoring the 2D vectorscope and image, make a minor adjustment to the gamma curves by doing one of the following:
   • To modify R, G, and B gamma values individually across the entire luma range (from black to white), click and drag in the Gamma R, G, and B fields. Drag left to increase contrast or right to decrease contrast. You can also enter a value directly in these fields. Enter a low value to increase contrast or a high value to decrease contrast.

   Only the field you modified is updated. The gamma curves are also updated to reflect your changes. The gamma curve is offset from its dotted adjustment curve. Use the adjustment curve to make regional adjustments to the channel.

   
   

   (a) RGB Gamma Fields

   • To modify R, G, and B gamma values proportionally across the entire luma range (from black to white), Alt-drag the Gamma R, G, or B field. Drag left to increase contrast or right to decrease contrast.

   All three fields are updated. The gamma curves are also updated to reflect your changes. The gamma curves are offset from their dotted adjustment curves. Use the adjustment curve to make regional adjustments to the channel.

   TipTo smooth the contrast, you can increase the gamma (raise the curves) and then adjust the Black and White levels in the Basics menu.
   • To modify part of the RGB gamma or luminescence range rather than the entire range, use the Edit Mode box to modify the adjustment curves.

   Select:	To:
   Add	Add control points to an adjustment curve. With Add selected, click either the red, green, blue or luminance adjustment curve to add a control point.
   Delete	Delete control points from an adjustment curve. With Delete selected, click a point on the red, green, blue or luminance adjustment curve to delete it.
   Move	Move the control points. With Move selected, drag the points to move them.
   Zoom	Zoom in on the curves. With Zoom selected, drag over the curves right or left to zoom in or out. You can also press Ctrl+spacebar and drag in the curves to zoom.
   Rect Zoom	Zoom in on a section of the curves. With Rect Zoom selected, drag a selection box to zoom in on the area of the curves contained by the selection box.
   Pan	Pan the curves. With Pan selected, drag over the curves to pan the curves in any direction. You can also press spacebar and drag in the curves to pan.

   After dragging control points, the image and 2D vectorscope update accordingly.

To reset RGB gamma or luminance curves for all frames in the clip:

1. Do one of the following:
   • To reset individual RGB gamma curves, select R in one of the Channel Reset boxes next to the Gamma R, B, or C field.

   The gamma curve is reset along with its adjustment curve for all frames in the clip. Any control points added to the adjustment curve are removed.

   • To reset the R, G, or B gamma value for the current frame, Ctrl-click the GamR, GamB, or GamC field.
   • To reset RGB adjustment or luminance curve values for all frames in the clip, click one of the channel buttons (RGB, Red, Green, or Blue) or the Luminance button to display the curves you want to affect, then select Reset in the Reset box.

   The values for the displayed adjustment curves or luminance curve are reset. Any control points added to the adjustment curves or luminance curve are removed.

To clear RGB gamma or luminance curve values for the current frame:

1. Do one of the following:
   • To clear individual RGB gamma curve values for the current frame, select C in one of the Channel Reset boxes next to the Gamma R,B, or G field.

   The gamma curve value is cleared for the current frame, and the gamma curve is updated without affecting its adjustment curve. A keyframe is set with the reset values.

   • To clear RGB adjustment or luminance curve values for the current frame, click one of the channel buttons (RGB, Red, Green, or Blue) or the Luminance button to display the curves you want to affect, then select Clear in the Reset box.

   The values for the displayed adjustment curves or luminance curve are reset for the current frame. The curves' control points are distributed equidistantly along each curve. A keyframe is set with the reset values.