Red, Blue and Green Channels

[LindaS]

What can I accomplish by editing the red, blue or green channels. I read somewhere that putting a blur on the red could help with skin and, in fact, I have been doing that and it works great, but what else can I accomplish?

[GaryK]

Linda

The full use of channels is best in Photoshop, that is not to say that things can not be done in Elements. Photoshop just makes using them waaayyyyy easier.

Scott has an old "Channels in Photoshop" book (or some name like that) with tons of examples of things that can be done. Primalrily masking and colour correction.
Then there is Katrin Eisman's "Retouching and Restoration" book (also for Photoshop). Which many consider THE reference book for this type of work.

While I use them (mostly via tutorials) and can appreciate the power, I still need to come to grips with all the advantages.

One thing I have seen mentioned is that the blue channel tends to contain the noise, bluring this sometimes helps with noisy photos.

[Michel B]

Using channels in Elements is way more difficult than with PS... for a normal PS user. Elements users can do everything with channels even without additionals add-ons like channel mixer. For me, the PS options for channel are much less intuitive... And for books about channels for Elements, have a look at Richard Lynch's hidden power of Elements 4. (valid for recent versions, except the way to install the included tools).

Don't forget that the levels adjustment layers work on individual R,G,B channels. You are working in a RGB color space, which means any shade you can obtain is a mix of the 3 components. The paradox is that while your eyes have cells sensitive to R, G and B (same with your camera) and your display has R,G,B diodes, our brain rather sees the colors and tones in the hue/saturation/lightness system. To confuse matters worse, the signals transmitted from the retina to the brain are rather coded in a way closer to the L*a*b mode = brightness, blue/yellow and green/magenta balance. And when you have a look at the contribution of each R, G, B channel, you have a totally unnatural representation of colors, whereas the Hue/saturation/lightness is intuitive.
How to 'see' a channel in Elements? Just use levels and neutralize the 2 remaining channels by setting their output to 0 - 0 instead of 0 - 255 (bottom slider).
Now, you'll generally see that the blue channel is darker and much noisier, but apt to retain texture details, the green channel is cleaner and good for sharpening, the red channel has less texture (this can be used for skin masks)
A few uses of channels:
- black and white conversion simulating colored filters
- white balance adjustment (moving the center slider of the blue channel)
- better denoising or sharpening
- building simply excellent masks
- adding texture to clipped saturated colors (flowers...)

[Daviskw]

There are so many uses for channels;

Manipulating channels is often a good way to isolate and repair damage... Often damage is limited to a particular channel and copying from one channel to the other can work miracles.

As you have mentioned you can isolate areas of a photo for an operation. Blurring is one procedure to reduce color noise but it is often advantageous to sharpen one channel as opposed to another. Say you have a green forest in the background of a portrait. If you sharpen globally the forest becomes distracting. To limit this you could sharpen the red heavily… the blue less and the green not at all.

Something that is very hard in elements but not so in Photoshop is to apply channels to others with the ability to use layer modes…This can do wonders for skin tones and also to repair color shifts. Say you have a too light uninteresting skin tone… You could apply the green channel to the red and blue then change the blend more to luminosity and mask as needed. This could give depth to the color and luminosity of the face. You can also apply the green channel to the red bringing out depth in the sky…

Another great use is to reduce haze and fog…often haze is centralized in one particular channel. By applying or replacing parts of the faulty channel you can bring out detail…it works great.


As mentioned above B&W conversions is another use for channels although less so since adjustment layers have been added…But even now in some circumstances the use of blend modes applied to channels can change the luminosity values in a way the plug-ins cannot.

By far the best use for channels is in the construction of masks… Most every mask I make I use channels as a base or start. Remember masks are black to conceal and white to reveal. Every channel has the ability to be displayed in B&W.. Often one channel will have white and black where you need it. Then you can further manipulate these masks with levels or dodge and burn or painting using modes such as overlay. Then you can load the luminosity of the channel and paste it into a layer mask. Sounds complicated but it is easy after you do it a few times.

Could go on a lot longer...but I often do that too much..lol

Butch

[LindaS]

Thanks. There's lots of good info here for me to get started with.