Photoshop CS Example:
Curves & Channel Mixer
( plus simulation of Velvia film)
This example uses Photoshop CS because Photoshop Elements
does not support Curves and the Channel Mixer. Both of these editing
tools are very powerful. The Curves adjustment is very effective
on almost anything, but it is one of the only tools that is easily effective
on sky, clouds, and snow. The Channel Mixer will be used to simulate
Fuji Velvia film, which is a film that yields dramatic results. We
will also use the Luminosity Blending Mode on some adjustments. This
example makes use of adjustment layers, so first see the Layers
Page before trying this.
Fig. 1. Before
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Fig. 2. After all of the changes
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Channel Mixer to simulate Velvia film:
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Layer > New Adjustment Layer > Channel Mixer. In the
dialog box, you can simply accept the default parameters and click on OK.
(Make sure that Normal Mode is the default, and feel free to give a more
descriptive name.)
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The dialog box shown in Fig. 3 appears for the RED Output
Channel, with the Source Channel values originally set to 100, 0, 0 for
Red, Green and Blue. Change the Source Color values to 140, -20,
-20 for Red, Green and Blue, respectively. In general, these values
should add up to 100 as I do here, but any values can be used. Do
NOT click OK yet.
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Click in the Output Channel at the top of this dialog and
select the GREEN Output Channel. Change the Source Color values to
-20, 140, -20 for Red, Green and Blue, respectively.
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Click in the Output Channel at the top of this dialog and
select the BLUE Output Channel. Change the Source Color values to
-20, -20, 140 for Red, Green and Blue, respectively.
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Click OK. The result of this layer adjustment is shown
in Fig. 4.
Notes: If a less dramatic result is desired, try using
values of 120, -10, -10. For a more dramatic (very risky), try values
of 160, -30, -30. If some colors become too rich, while others are
great, consider changing one of the channels back to 100, 0, 0. I
have experienced this where the blue of the sky is too rich, so I keep
the Blue Channel at 0, 0, 100 for RGB. One of the better ways to
convert a color image to Black and White is to use the Color Mixer and
to also check the Monochrome box at the bottom of the dialog box in Fig.
3.
Fig. 3 Channel Mixer dialog
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Fig. 4 After Channel Mixer adjustment.
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The colors in Fig. 4 look good, but the sky and snow capped
mountains look a little pale. Do not use a Contrast adjustment on
the sky and snow because the light areas will get lighter. We will
use Curves.
Curves Adjustment of the sky and snow capped mountains:
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Select the sky and the snow capped mountains very carefully
and accurately. See the Selection Page
for details. It is very likely that you will need to use a combination
of selection tools and you will need to zoom in so that you know that you
have an accurate selection.
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Save this selection by Select > Save Selection, then give
it a name, such as Top Stuff. After all the time you spent, I recommend
saving it if there is a possibility of using it again, and we will.
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Select > Feather. Input a very small number, such as
1 or 2. I used 2 in this example.
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Layer > New Adjustment Layer > Curves. In the dialog
box, change the Mode to Luminosity (from the default value of Normal).
This is very important if you like the current colors. Click OK.
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The dialog box in Fig. 5 appears, except that there is a
45 degree straight line drawn. I first dragged the curve downward
on the left side (dark side), and then I dragged the curve upward a little
on the right side (light side). With all adjustments, toggle the
Preview to see what is going on.
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Click OK. The resulting image is not shown here at
this stage, but the results are displayed in Fig. 2 above by looking only
at the top part of the image.
Notes: The horizontal axis represents the Input (or
the original) colors from dark to light as you go from left to right.
The vertical axis represents the Output (or resulting adjustment) colors
from dark to light as you go from bottom to top. When the curve is
below the original 45 degree, the resulting adjustment gets darker.
If the curve is above the 45 degree line, the results are lighter.
In this example, the dark and midtone areas will become darker, but the
very light colors will not change much. Unless you are trying to
do some very creative adjustment, the curve should never be decreasing.
Fig. 5 Dialog box for the Curves adjustment
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Velvia film has rich color saturation and it has a little
more contrast than many other films. As noted earlier, we did not
want to add any contrast to the sky or snow, but we will add a little to
the remaining portion of the image.
Add some contrast to the rest of the image:
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Select > Load Selection and then select the Top Stuff option
from the drop down menu. This was the selection we saved earlier. Click
OK.
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Select > Inverse. The "inverse" is the "complement"
of the Top Stuff region.
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Select > Feather. Input a very small number, such as
1 or 2. I used 2 in this example. For this example, it is generally
better to use the same feather value as you used for the previous adjustment.
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Layer > New Adjustment Layer > Brightness/Contrast.
In the dialog box, change the Mode to Luminosity (from the default value
of Normal). This is very important if you like the current colors.
Click OK.
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Move the Contrast slider to the right, I used a value of
12 in this example.
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Click OK. The result is shown in Fig. 2 above.
Note: The increased contrast darkened the very bottom
of the image to a point where very little detail is visible. That
was intentional because I wanted a very strong shadow to balance the bright
white regions of the snow, and because the detail was not very interesting.
To avoid making it that dark, you could modify the selection to exclude
that area before applying the contrast adjustment. You could also
bring back a fair amount of detail after the fact by using the Shadows/Highlights
adjustment.
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