Graphics Reference
In-Depth Information
Looking at the histogram itself, there's really no way of telling what
to do with your midtones. The shapes in the histograms in the middle
of the graph seem to be lining up pretty well. At this point, the image
seems a little magenta in the midtones. You can use the gamma con-
trols for the individual channels to tweak the image using your eyes
on the video monitor to complete the correction. Remember, if you see
magenta in the midtones, you need to either lower the red and blue
of the midtones or raise the green of the midtones because red and
blue make magenta and green is the opposite of magenta. Which you
use depends on whether you want to raise the overall feel of the mid-
tones or lower them. If you add green to counteract magenta, you will
also be increasing the level of the midtones. If you lower red and blue
equally, you will be reducing magenta
and
reducing the overall level at
the midtones.
In reality, you simply don't use a single tool to guide you through an
entire correction. You have to rely on how the image looks in the video
monitor and compare that with the information you're getting from the
RGB Parade waveform and the vectorscope. You can check out images
that have severe problems with histograms to get an idea of what might
be wrong with a specific channel, but most colorists would be able to
glean this same information from the RGB Parade.
Eyedropper
One of the relatively new and very precise methods of analyzing color in
most of these software-based color correction applications is to use the
eyedropper.
Apple's Color and Final Cut Pro, Avid, and Color Finesse, among oth-
ers, allow you to see the numerical values for sampled pixels. This is
valuable information. The eyedropper allows you to sample very precise
sections of the image. The big caveat to the eyedropper is that it depends
on the specific pixel you sample. Some apps—like Avid—allow you to
average the eyedropper sample across a 3 × 3 grid of pixels around the
exact tip of the eyedropper. Other apps allow you to choose a 5 × 5 grid.
This averaging is usually a good thing, because noise and other odd varia-
tions can mean that the exact pixel you chose isn't really representative
of the other pixels that appear identical around it. The danger with the
larger sampled grids is that they can include pixels of very different colors
that are adjacent to the one you chose. For example, if you sample near
the edge of a dark line, the sample grid of 5 × 5 pixels might be reading
half of the pixels on the bright edge and half the pixels on the dark edge,
giving you a reading that really doesn't correspond to either area.
Aside from those caveats, eyedroppering can give you some very good
information about your picture. For this tutorial, we'll use Color Finesse.
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