2 was inspired by Keith Meacham, whose recent posts were excellent candidates
for a little color correction to reveal their true potential. In this
lesson, we'll explore the use of some of the more basic color correction
tools Paint Shop Pro 7 has to offer. Comments and questions, as always,
Lesson 2 - COLOR CORRECTION
Does your favorite WC locomotive look a little green
behind the gills after scanning your prized shot? Seeing things through
a haze of blue? Perhaps that vintage Milwaukee road shot has more orange
than the 1871 Chicago fire. What do you do? Unfortunately, incorrect
color reproduction is quite common. Fortunately, it is easy to correct
with the right tools.
Improper color reproduction is a problem that can effect both
film and digital cameras alike. Scanners, although less susceptible,
can also succumb to the inaccurate colors under the right conditions.
Even the human brain can be tricked to see colors incorrectly (go look
through a piece of heavily color piece of plastic for several minutes covering
only one eye, then compare the difference between both eyes). Why does
this happen? The light source illuminating your subject may not be
pure white light (i.e. Fluorescents give a greenish hue, Sodium high pressure
lights will produce a very monochromatic yellow). Another cause may
be that the colors are being interpreted incorrectly by the camera or by
the developing process. Luckily, Paint Shop Pro has several tools to
help compensate for this problem.
Automatic Color Balance Tool
Probably the most simple and effective tool that PSP has to offer is the Automatic Color Balance
, located under Effects >> Enhance Photo. This is probably one
of the most useful commands for those of us who use PSP for photography.
If it's not on your customized toolbar, I recommend adding it as you
will probably find yourself using it a lot. Examining the command
dialogue, the controls are fairly straightforward:
You have a sample of your original image on the left, along
with a preview window on the right. Below, you can set the strength
of the tool, and have the option to remove a color cast (more on this in
Then we get to the primary control. Here we can adjust
for the color temperature to that of our desired light source of correction.
The illuminating light color is expressed as temperature, in
units of Kelvin (Celsius + 273 degrees). This measurement is
derived from comparing the color of light emitted from an incandescent light
bulb filament, such as tungsten, at various temperatures. The lower
the temperature of the filament, the more orange of a light that will be
emitted, conversely, the higher the temperature, the more bluish the light
will become. A tungsten filament is not capable of emitting much more
than yellow light, as tungsten melts at around 3500K. The higher temperature
values are usually a projection of the light color v/s temperature correlation
from the incandescent filament. Fortunately, we don't need a big drawn
out conversion chart as the nice folks at JASC have conveniently marked several
points on the slide that correspond to common light sources.
In this first example, our subject was shot in early evening
light. Sunlight near dawn and dusk takes on a much stronger yellow
to orange-red tone. As a result, contrasting hues such as blue will
lose some of their purity, taking on a yellowish, or even orange appearance.
To get a healthier looking sky in this case, we will simply set
the color temperature to 6500K or sunlight and click okay. The result
image has the yellowish cast removed, yielding a much more blue looking
sky. Even so, the gold on the locomotive has not lost any noticeable
degree of color saturation in the gold.
Figure 1. The uncorrected image exhibits a yellowish cast from the early evening sun.
Figure 2. After correction, the sky takes on a more normal color, yet the gold on the locomotive remains unharmed.
In some more severe conditions, you may find your image looking somewhat
devoid of color. The auto balance only compensates for the apparent
shift in color, but not the strength. Therefore, some colors
may have been more suppressed by the illuminating light temperature. To
compensate for this, you can simply increase the image color saturation
using a tool that is a close neighbor to the first, the Automatic Saturation
Removing Color Cast
When shooting with a light source that is far removed
from white, your images will usually end up with much more emphasis
on the illuminating light source color, even showing up in areas of color
that would normally contrast with that particular color. Shooting under
certain types of artificial light (such as Sodium high-pressure, or Mercury
Vapor) or even just scattered skylight can cause this problem. In
the example below, a simple color balance to sunlight does little to
fix to overall blue cast. Why? The auto balance tool already
recognizes that most of the scene (the sky) is already inline with where
it should be in regard to the color temperature for sunlight. What
it is ignoring is that some areas are showing signs of over saturation of
the apparent illuminating light temperature. By checking the Remove
Color Cast box, the auto balance tool now watches for areas that appear to
be weighted heavy towards the overall color makeup of the image and corrects
Figure 3. The uncorrected image. The locomotive's shadowed side takes a blue cast from the scattered skylight.
Figure 4. An automatic balance at 6500K does little to fix the problem.
Figure 5. By having the auto balance feature remove the color
cast, the blue that was affecting the color of the locomotive is removed.
The trade-off is that the sky appears less vibrant, however an appropriate
amount of sky color can be recovered using the Automatic Saturation Enhancement
tool if desired.
The remove color cast tool can also help reduce blue glare that is sometimes
present in photos in direct sunlight. Some types of film, and especially
digital camera CCD's are more sensitive to ultraviolet light than visible
light. As a result, you may develop a blue cast in particularly reflective
areas, such as white. Normally the best fix for this problem is to
use a UV filter, but due to many lens designs, installing a filter may not
be a viable option. In such cases, a color balance with the color cast
removal can lessen the effect of UV exposure.
Manual Color Correction
At times, particularly with older scanned photos, it will be difficult
to determine an appropriate light source temperature to correct to, or the
colors may just seem to be so far out of whack that you may be unsure where
to start with your color adjustments. Here, Manual Color Correction tool
enters the picture. Like the automatic color balance, this
tool will shift red, green and blue saturation levels. Unlike the automatic
color balance, you provide the tool with a swatch of the image and provide
a known color reference for it to use in identifying how to shift the values.
In the dialogue box for the Manual Color correction tool, you
have the original image on the left, and the preview on the right. On
the left image, you select a portion of the image that you know the proper
color value, or can make a reasonable assumption of what the color should
be. You then go below and select a category, in this case sky colors,
and then pick one of the presets. You can see your immediate results
in the preview box so you can experiment with different presets.
Two options available are the preservation of the color lightness
and the preservation of the color saturation. Checking preserve lightness
tells the tool to ignore the difference in brightness between your selected
area and the preset and just correct the red, green, blue color ratio.
Checking the preserve saturation will cause the tool to ignore the difference
in color saturation between the selected area and the preset.
PSP provides a fairly decent selection of presets in a number
of categories that are common to most pictures. Even so, I have
over time developed my own presets in the User colors, tailored specifically
for use with train pictures. I have created a handful of WC gold and
maroon presets under various light conditions and paint conditions. While
my digital photos typically never get this bad that I need to resort to manual
color correction (I use the automatic balance quite regularly), the
references are very handy when attempting to correct scans of pictures.
After color balancing and correction, you will likely want to perform additional
image enhancements, such as the Automatic Saturation Enhancement or some
light Gamma Correction to get the colors and details to be a little more
vivid and revealed. Again, this is normal for virtually any image that
requires color adjustment.
So, there you have it. Now you know how to keep your skies looking
crystal blue, your golds nice and rich, and your maroons nearly as accurate
as the paint formula itself. Color correction is one of the most basic
tools that can bring out the best colors your photos have to offer.
Until next time, happy experimenting!
©2003 Ray Meyer