Image Processing Reference
In-Depth Information
Color Correction
The luma and chroma settings should already have been equalized throughout the whole
movie as part of the grading process during the movie production. On the other hand,
you may be working on some original footage that you shot yourself. That grading
process must still be done to average out the overall picture brightness and color
throughout the movie.
Color-Correction Tools
Figure 35-9 shows a screenshot of the color corrector from Final Cut Pro. An amazing
amount of control over the video is possible. This will rescue grossly underexposed
footage that might have been unusable otherwise.
If you are getting into color correction, this must be applied sparingly and in differ-
ent ways at different times in the movie.
This color corrector operates on the video content by working on blacks, mid-tones,
and whites as separate ranges. Other color correctors have fewer controls and work in dif-
ferent color spaces.
For each range, you have control over the hue and brightness and the overall satu-
ration. On this control pane, you will see other buttons and presets. You can pick a color
in the image with the eyedropper and use that as a handle to pull the pixel value to a
desired setting. Other color values for the remaining pixels in the image have their values
interpolated from that. To remove a yellowish cast from an image, choose the lightest pixel
that is a pale yellow but that should be white. Then use that as a reference pixel and the
color corrector will compensate by removing that amount of yellow from the image. The
effect will be applied proportionally to darker values.
Color Calibration
Find the Mac OS X digital color meter in the utilities folder that was discussed earlier. This
is useful for getting RGB values in the raw and preview windows in order to adjust the
brightness and contrast settings. Measure the blacks and the whites and check that there
is no crushing.
If you can only afford one moderately expensive tool apart from your compression
software, then buy Adobe After Effects. Version 6.5 is especially good for processing bad
video. Even though it is a tool designed for creating special-effects shots, it does give you
some leverage with corrective filtering.
International Color Consortium:
Search WWH ::

Custom Search