Color Correction - Nuke 101: Professional Compositing and Visual Effects - page 178

2. In CurveTool1's Properties panel, switch the Curve Type drop-down menu to
Max Luma Pixel.
3. Click the Go! button.
4. In the dialog box that opens, click OK as you only want to process one frame.
5. Switch to the MaxLumaData tab and view CurveTool1 in the Viewer ( FIGURE
4.30 ) .
Figure 4.30. The MaxLumaData tab's two sections.
The purpose of this operation is to find the darkest and lightest pixels in the im-
age.Whenswitchingtothistabyouseetwosections,theoneshowingthelightest
pixel (Maximum) and the darkest pixel (Minimum). For each, the X and Y loca-
tion and RGB values display.
Looking closely you can see that the value of the minimum pixel is 0 in every
property. This is because this image is a premultiplied image, and as far as
CurveTool is concerned, all that black in the image is as much a part of the image
as any other part of it. You need to find a way to disregard that black area. Let's
do the following.
Note
A Constant node creates a solid color with a chosen resolution.
6. From the Image toolbox, create a Constant node.
7. Change Constant1's Color value to 0.5.
8. Select Read1 and branch a Merge node from it by pressing Shift-M.
9. Connect Merge3's B input to Constant1, and then view Merge3 in the Viewer
( FIGURE 4.31 ) .
Figure 4.31. The car is on a gray background.