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This image is a color channel reverse for the image
shown on page 4. See a larger sample of both images.
I love this effect - could so easily have been taken late in the evening
instead of in the sun.
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You now know how to split channels apart and merge the pieces back
together. Plus, you understand how to view channel changes in the main
screen (Photoshop only). But what can you do with it?
There are two main areas where channels can carry a heavy load: enhancing
images and special effects. Let's take a look at just a few little techniques
to get your mind going in the right direction. Perhaps the best idea
would be to think in tiny amounts. If you are working on an enhancement
and everything you do is too heavy handed, think channels. For special
effects, your assignment is just to play. Tough job, but someone has
to do it and it is the best way to understand what you can do with channels
and effects.
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Over sharpening a color channel will adjust the color
in your image. The green channel in the lower image was sharpened severely.
The lower corner of this image contained many artifacts
from earlier compression. Selecting the offending pixels on the red
channel, and filling with a solid color, helped a lot. See the image
above this one for the result.
Photos © Tom
Thomson Photography.
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Image enhancement
I shudder when I remember some of the photos I have received from clients.
I do have a standard "professional quality" clause in my contract,
but I am a softee. Plus, that terrible image may be the perfect one
to communicate an important message. The Channels feature has bailed
me out on many occasions.
Check back to page 4 and see the subtle enhancement
I did to an image to pull out a little more detail in a tree. By sharpening
only the green channel, the needles popped out just a bit, and over
the entire image, really improved it. However, be careful with what
you do.
This poor image has been worked a little hard, but I wanted to show
you what happens when you have a heavy hand with channels work. When
you sharpen a full image, color is really not in play other than to
sharpen the detail in your image. However, when you are sharpening a
channel, you are affecting only one color in the image. Over sharpen
the RGB image and you will get ghosting around your detail. Over sharpening
a channel and your ghosts will gain color ... quickly.
In the image at the left, the lower image has had the green channel
drastically over sharpened. As the green in the channel reduces or increases
from the sharpening, the red is affected (green and red are inversely
related in an image - increase one, the other goes down). You must be
very careful with manipulating a channel. Chant 'subtle, subtle, subtle'
as you apply filters or adjustments to a channel.
Things to keep in mind for enhancing images are sharpening, removing
(or adding) noise and sometimes a subtle (note that word) blur on a
channel will work wonders. I have used that when I need to sharpen an
image, but one color in the image ghosts when I apply the sharpen to
the full image. Soften the offending channel, and try again.
Experiment. Take a lousy image and see what you can do with it. If
you are having trouble exporting an image to JPG or GIF format, try
adding a little noise to the channel that may be banding or doing other
bratty things on export.
I have included a little sample of a semi-fix I did to the image above
the screen shot. That corner was gathering artifacts with a vengeance.
I went back to the red channel and selected the corner pixels and feathered
the selection. I then used the eyedropper to pick up just one color
from the selected area and filled the selection with that color. It
was not a miracle cure, but the final image is slightly better than
it is in the before sample in the screen shot.
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One filter for two effects. The first image was created
with the Circle filter in Paint Shop Pro. The lower image had the same
filter applied to only the green channel.
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Special effects
Here we get to play. Applying a filter to one channel offers wonderfully
unpredictable results. You have seen the results of exchanging channels
earlier in this tutorial, but you can also use any filter.
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The images at the left are manipulations of the image shown to
the right. (Click on the image at to see
a larger view of the original. Great shot) The top image
has had the Circle filter in Paint Shop Pro added to the RGB image.
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The lower image is the same filter, but applied only to the green channel.
Interesting results. In the matter of a few minutes, I had a selection
of effects created by applying just one filter to many different channel
combinations.
I am certainly going to return to this subject at a later date. We
spent most of our time here with basic techniques, but I have much more
to show you. Watch for the sequel.
In the meantime, set aside a little time to practice working with channels
to enhance the quality of your photos. Then reward yourself with some
time to play with filters in channels. A whole new world awaits you.
Have fun.
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