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What is equalization? |
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Theory |
Basically equalization means that
you take a look at the overall impression of the image (its histogram)
and accordingly change the values of the pixels so that there is
an equal distribution of values across the entire range. For example, if a grayscale image is predominantly
gray with no highlights and deep shadows, equalizing will change
the image so that there is an equal amount of shadow, midtone and
highlight. It is obvious that this in its simplicity is a crude
operation that can both ruin or improve a picture. Please see examples
with histograms below.
Equalization is a traditional image transformation that has not
been improved upon since it's invention decades ago. Power Retouche
offers a great improvement to equalization.
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Equalizing a color image |
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Examples |
This example is rather dark and
without contrast. As you can see from its histogram, as well as
from the image itself, it is dominated by a large mass of darkness
and no real light. Equalizing will change the histogram, so there
is equal amounts of the various levels.
Please compare with the example of traditional equalization to see
the great improvement Power Retouche offers over the traditional
method. In order to compare, we equalized 100%, because traditional
equalization offers no means of adjusting the amount. In an actual
retouching situation, this image is over-equalized and about 50%
would have been appropriate. Also note that Power Retouche equalization
does not posterize the histogram, like traditional equalization
always does.

Original image
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Original images histogram
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Luminance equalized with Power Retouche (100%)
Photographic mode. This mode usually preserves more details;
observe the small hairs on the leaf.
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Histogram without anti-posterization
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Luminance equalized with Power Retouche (100%)
Not Photographic mode. In this case
100% equalization is too much, but for the sake of illustrating
our unique histogram, please compare to below image.
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PR Equalized images histogram
without anti-posterization
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Equalized traditionally (all colorchannels)
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Traditionally equalized images histogram
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Equalizing a grayscale image |
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Equalization can produce very aesthetically
pleasing results when used on grayscale images.
Simply equalizing a grayscale image at 100% will superficially produce
similar results with Power Retouche as with the traditional method,
but Power Retouche will be far less posterized. Traditional equalization
offers no advanced retouching options, like the ability reduce the
amount or to equalize some part of the image more then others. Below
is an example of equalizing with Power Retouche graduated effect,
where the lower area is more equalized than the upper. This graduated
effect produces a far more satisfying retouch as it gives great
depth to the image and more variety of texture.

Original grayscale image
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Original images histogram
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Equalized with Power Retouche (100%).
Equalizing with traditional equalization will produce an almost
similar result, however the traditional will be far more posterized.
Actually equalizing this image 100% is too much; please see
example below...
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Power Retouche without anti-posterization

Traditional
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Equalized with Power Retouche (50%).
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Power Retouche without anti-posterization

Power Retouche with anti-posterization
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Amount of equalization
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Amount
of Equalization
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This
slider simply lets you control the amount of equalization. This
is unique to Power Retouche as regular equalization does not allow
for this.
As you can see in the example below, Power Retouche equalization
can greatly enhance an image, but 100% may be way too much. In this
case 40% is appropriate.

Original image
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PR Equalized 40%
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PR Equalized 100%
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Photographic mode |
This option will generally give
a more natural look to the equalization. Near highlights and near
blacks will remain unchanged.

Original image
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Photographic mode
Equalization = 100%
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Retouch levels |
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Retouch
levels is common to most Power Retouche plug-ins. The sliders let
you control the amount of equalization to apply to lights, midtones
and darks.
You can for example use this as a means to bring details out from
the dark. Unlike the Shadow/Highlights adjustment in Photoshop,
this will not create halos.
Compare to equalizing uniformly for lights, midtones and darks,
but using Photographic mode instead (see above).

Original image
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Equalization = 100%
Lights = 0
Midtones = darks = 100
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Original image
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Equalization = 60%
Lights = midtones = 0
Darks = 100
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Graduated effect |
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These
controls are common for many of the Power Retouche plug-ins. Using
graduated effect will cause the filter to apply it's filtering at
full strength in one side of the image and then fade the effect
out towards the other side. You can change direction by right clicking
the preview. Midpoint will shift the balance between how large an
area will be filtered at full strength and how much will have a
faded out effect. Contrast will change the acceleration and spread
of the fade-out.

Original image
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Uniformly equalized
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Graduated equalization
towards upper right corner
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Color range |
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Use
Color range |
This
is also common for several of the Powerretouches.
Color range will restrict filtering to colors in the range from
the right side of the "From" slider to the left
side of the "Up to" slider. This also if the "from"
slider is to the right of the "to" slider. If you only
selected what was in between, you would not be able to select everything
except red (for example).
Mask unchanged will apply a mask over areas outside
the range.

Original image
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Illustrating the mask
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Equalized 100%
Lights = 100%
Midtones = 100%
Darks = 100%
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Equalized 100%
Lights = 100%
Midtones = 50%
Darks = 0%
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Softness |
This slider determines if the changes should be applied evenly
to the selected color range or if (and how much) it should fade
out towards the extremes. |
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