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GRAPHICS KNOWLEDGE

ò Channels by SPYDERIX
Posted: 23 May 02 (Edited 26 Jun 03)

I am going to make this as simple and painless as possible.

Channels are the different colors that make up a picture.
There are 3 channels in an RGB image (Red-Green-Blue)
&
There are 4 channels in a CMYK image (Cyan-Magenta-Yellow-Black)

What is a channel?
When you look at a colored image on our monitor, you are actually looking at a combination of ONLY three colors: Red, Green and Blue. It is a combination of the three colors that produces the millions of colors we see.

By using channels you can go through a process of color separation in order to enhance your graphics. Channels can be used on any type of image, but photographs are the best types of images to use channels with.

Do you have a picture that needs that extra touch but you can't seem to figure out what filter to use. Lets say you want to add a bit of sharpening and some blur, and maybe a hint of noise, but when you use the filters you get a horrible looking picture and ghosting may occur around parts of your image that you don't want. That is because you are applying the filters to the image as a whole and not as a channels (seperate colors).

Instead you should be using the various filters on only the colors you need to. If you have a nature scene with blurry looking trees and a really dark looking stream flowing through, you can do two things: 1-split the channels or 2-work right out of the channels window. Then add the sharpen filter to the green channel and change the brightness/contrast for the blue channel. Then you can either view the picture in the layers window or merge the channels back together, depending on what method you used above and you get a prestine looking image.

BE VERY CAREFUL WHEN APPLYING FILTERS TO CHANNELS AS OVER-FILTERING OCCURS VERY EASILY.

To work right from channels window
Simply goto WINDOW|SHOW CHANNELS, or WINDOW|CHANNELS depending on your version of Photoshop and then click on the channel you wish to work with then make your adjustments and then when you've finished click on the first channel layer (RGB, or CYMK), and then goto back to the layers window. With this method there is no need to flatten the image.

How to split channels
First of all you can only split channels when the image has been FLATTENED goto LAYER|FLATTEN IMAGE, or click on the little triangle button in the layers window and goto FLATTEN IMAGE.

Then goto WINDOW|SHOW CHANNELS then click on the little triangle in the channels window and click on SPLIT CHANNELS. Your image will disappear and 3 new windows will popup all in grayscale. You can identify each channel by the title. It will have the name of your image (or untitled) then the corresponding letters of your image type (RGB images will split into 3 windows one will have an "R", one will have a "G", and the other will have a "B", and CMYK images will have a "C" on one, a "M" on one, an "Y" on one, and a "K" on the other.) Now is the time to start adding filters to each channel.

How to merge channels
After you have finished playing around with the variuos filters, you will want to merge the channels back together. To get back to the image you had before filtering, click on any window and then click on the triangle on the channels window and then goto MERGE CHANNELS. Now you will be prompted with a couple of little windows. The first one asks for the Mode and the number of Channels. If you are working with an RGB image, set the Mode - RGB and Channels - 3, if you are working with a CMYK image set the Mode - CMYK and Channels - 4. Then hit ok. You will be prompted with a new window now asking you to specify the channels. Now this is where it gets interesting: if you want your image to look exactly the same as before you split the channels then just hit ok (the channels should be in the order R-G-B) However you can have a bit if fun and re-arrange the channels to get an interesting looking picture. TRY IT OUT TO SEE WHAT I MEAN!!!

Have fun!
Thanks "blueark" for your contribution!


NATE


http://www.mainframe-webdesign.com

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