The Scopes panel is relatively new to Nuke. It offers a standard set of tools for evaluating the color of an image.
- The Vectorscope
This visualises the hue and saturation values of an image. In the middle there is a lump that extends from the centre. The distance that the lump extends from the centre represents the saturation of the image: the further out, the more saturated the image is. The orientation of the lump (i.e. what 'o'clock' it is) represents the hue values. In the example shown, the image is clearly very blue and cyan, with some purple and a tiny bit of yellow.
- The Vectorsope
This visualises both the RGB values of an image, and its luminance (i.e. its brightness). I most commonly use it for the later. I will describe how to use this tool in class.
- The Histogram
Histograms are found in multiple applications. They are most commonly used to evaluate the lightness values of an image. Histograms are described in this page (from my Photoshop wiki).