Graphics Reference
In-Depth Information
that same area of the trace in the blue channel up to match them. My adjust-
ment was to bring the point at 185 on the blue curve up to 207. When I did
that, I also brought the highest highlights on the blue channel up too far, so
I made an adjustment at the top point of the blue curve back down to 246.
You could look at the RGB Parade and decide that the highlights in the
red channel are too strong, but I think that the extra “weight” at the top
of the red channel trace on the waveform is probably due to the red and
pink flowers that are in a corresponding position to the strongest parts of
the red channel of the waveform monitor. If you want to, you could play
with the red channel to get it back into line with the blue and green chan-
nels, but you'll see that the white highlights in the picture quickly turn
cyan, which is the opposite of red.
The image looks significantly better at this point. But there's a lot of green
in the tin flower can on the bench and I don't think the green foliage pops
very well. Let's see if we can pull out some of the green in the midtone areas.
Start with a point in the green curve that's about halfway up and pull
it down a little. Using the information in the tip box on this page (in the
margin to the right), you know that you're moving the midtones of green
down, so you need to be looking at the midtones of your video image
to prevent the image from going too magenta, which is the opposite of
green. As soon as you see the midtones turn magenta, you have to back
off the correction. For me, the magenta cast started almost immediately
when I pulled the gammas down, so I returned it to its original place.
(Undo—Command-Z or Control-Z—should work on most applications,
or you can select the point and delete it.)
I still feel that there's a bit of a green cast to the middle shadows, so
this time, let's place a point that's much lower on the green curve and pull
it down subtly. I brought the point from around 106 down to 57, which
may not seem like a very subtle move, but remember that the black level
of green was already pulled down quite a bit, which pulls down all of the
other points on the curve as well.
Looking at our original image (
Figure 4.47
) compared to our correc-
tion shows a significant improvement (
Figure 4.48
)
. These are changes
that would not be quite as easy to make using the traditional hue offset
wheels because the changes to the midtones of the blue and green chan-
nels wouldn't work as well as the specific changes we made to the high
midtones of the blue channel and the low midtones of the green channel
(
Figure 4.49
)
.
The important thing to remember when choosing a point is to deter-
mine a specific portion of the picture you're trying to change—like the
tin watering can in the previous example—and to try to guess where that
tonal range lies on the curve. Don't be afraid to make mistakes. Pick a
point and move it a bit. If it's not affecting the tonal range you want, then
delete it and pick another point. Use the information you gathered from
T I P
Whenever you are making
a correction, be aware of
what tonal range you are
adjusting and which color
you're adjusting. When
you're looking at your
video monitor, you want
to be especially tuned to
the subtle changes in that
specific tonal range and
with that specific color.
Sometimes if your eyes are
looking at the entire image,
you'll miss subtle changes
that you would notice if
you were looking in the
right place. You also don't
want to be blind to what
the correction does to the
larger image. Sometimes
this means tweaking the
image back and forth look-
ing at just the shadows the
first time you tweak it and
then at the overall image
the next time you tweak it.
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