Selections In Photoshop Using Channels
By  Andrea Michael
Using channels is a great way to make precise and intricate selections in Photoshop. There are other ways to make selections, such as the lasso, marquee and paths, but I prefer using channels for two reasons: its easier than the others once you know how to do it, and I feel there is more control over which parts you want to select. At the end of this article I shall also explain how to use channels with lighting effects in a simple little exercise to create rather interesting results. This tutorial is based around Photoshop 4, but is basically the same in 3, and I assume, 5.
Making Selections:
1. Open a picture in Photoshop. For the purposes of this exercise, please make sure it is in RGB mode so there are 4 channels existing already: RGB, Red, Green and Blue.
2. Decide which area you would like to make a selection around (ie, which are you want the "marching ants" to border).
3. If the Channels palette is not open, click on Windows, Show Channels.
4. You should have a palette on the screen in front of you with the 4 channels mentioned earlier - RGB, Red, Green, Blue. If these channels are missing, you might not have an RGB image open. If this is the case, simply change the Mode (found under Image), to RGB. 
5. To make a selection using channels, we must make a new channel. Click on the little arrow at the top right hand side of the Channels palette and click New Channel.
6. A box will appear on the screen called Channel Options. You can leave the channel name as #4, but make sure that under Colour Indicates you select Masked Areas. The colour can be anything you want, but for the purposes of this exercise I will assume it is red. Please make sure that the opacity is at 50%. Click OK.
7. The image will go black once you have clicked OK. Don't panic, your picture is still there. You will see a little image of an eye in the Channels palette on the left hand side of the channel you just created. There is a section on each channel for this eye. Click on these little areas to activate the other channels. You should now have 5 channels with eyes to the left of them.
8. Your picture should now look as though it has a see-through red layer over it. 
9. In the tool bar, right down the bottom, there are the foreground and background colour boxes. Make sure they are black over white.
10. Double click the eraser tool to choose what type of eraser you wish to use and also choose the brush size. For large areas, you can use the block or a large brush and for tiny, intricate areas, you can use use the pencil, paintbrush or airbrush and small brush sizes. As you can see, this will give you utmost control over your selections.
11. Using the eraser tool, start erasing the red off the area you want to make a selection around. If you make a mistake and erase a bit of red that you didn't want erased, simply reverse the foreground/background colour boxes on your tool bar so the white box is on top of the black. You do this by clicking the double-ended arrow to the right of these boxes. You can then paint the red back over the area you accidently erased. 
12. Once you are satisfied with the area you have erased, turn the eye off in the channel you have made (#4) and activate the RBG channel at the top (it will activate the other three) by clicking on it. The red layer should have disappeared.
13. Click on Selection at the top of your screen, then Load Selection and load channel #4. The area of red that you erased should now be a selection of the same size and shape right where you wanted it. You can load this selection at any time as it has been saved as the channel you made. You can make as many selections in an image as you like this way, but as with, the more you have, the larger your filesize will be. 
14. When you have finished creating the picture and no longer need the channels, drag each one down to the little trash can icon at the bottom of the channels palette. Photoshop will only allow you to save the image as a .psd if you keep the channels.
Lighting Effects and Channels
Using the above method to make a channel, we can now use it in a fun and easy exercise that can create some very interesting effects.
1. Go through the process detailed earlier to make a selection using a channel. For the purpose of this exercise, do not actally have the selection loaded onto your image, we only need the channel.
2. Click on Filters, Render, Lighting Effects. This will bring up a Lighting Effects dialogue box.
3. Down the bottom of the dialogue box is a drop down menu titled Texture Channels. Select the channel you have made, ie #4, and watch what happens. (Make sure preview is selected).
4. You can adjust the 3D effect as much as you wish with the different lighting styles and colours, and by adjusting the slide bars. Just mess around and have fun, you can create some really great effects!
Here is an example of the type of effect that can be created using the process I just detailed. 
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| |  | Inside Adobe Photoshop 5.5
In Inside Adobe Photoshop 5.5, Gary Bouton's learning methodology is set up to give you hands-on experience with Photoshop's features, using either the imagery created in the book or the user's own. Gary goes well beyond simply reviewing the features and grounds his readers in the most practical and useful aspects of Photoshop-the real-world uses of this powerful program-before delving into the more complex, arcane, or esoteric uses of the program. Each chapter includes a balance of textual... read more |
| |  | Adobe Photoshop 5.5 Classroom in a Book
Designed to instruct you on the variety of tools available in Adobe Photoshop 5.5 that will help you produce sophisticated graphics for the Web and print. Each lesson provides step-by-step instructions for creating a specific project. Softcover. CD-ROM included. |  |
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