I was having a play in Photoshop with some older images I have (shoeboxed) to see if I could apply a high-key effect to them. I was surprised to find that I could get quite a few of my portrait type shots to work with a high-key effect. It does not work for all images; it really depends on the lighting. High key usually works better for portrait shots of people.
Here is what I did in Photoshop to get the high-key effect; I am sure there are lots of other ways to go about this, as there are for many things in Photoshop. Open the image you want to work with in PS, then open the Channels palette, it may be attached to your layer palette or you can find it under the Windows /Channels in PS.
Now that you have the channel palate open, select the red channel only. You do this by clicking the little eye icon next to the green and blue layer. You should be left with the red channel showing only.(see below) This tends to be the lighter of the three colour channels in general, which means it holds the most information. If the green or blue channel is lighter, then you can choose that layer to work from. Now take the red channel back into the normal layer palette. You have to make sure that the red layer is highlighted in blue as below. Press Ctrl + A (this selects the layer) then press Ctrl + C (this copies the selected layer). You can now click on your normal layer Tab.
Now that you are back in the normal layers area, Create a new layer so you can paste the copied red channel into it. Select the new layer icon at the bottom of the layers as below. This will create a new layer, if you press Ctrl + V this will paste the red channel you have just copied into the new layer.
now we want to duplicate the new layer that we just created, right-click the new layer in the layer palette and choose duplicate layer.
With this duplicated layer, change the blending mode of the layer to Screen. If you choose the drop down arrow where it should say Normal, simply go down and select Screen.
After doing this, you should see the whole image get brighter, more than likely too bright! You will now need to alter the fill percentage of this new layer to darken the image to the point you want. This really depends on the image you start with. Just move the slider along till you get to a point you like. You can always tweak this later on.
I now added one more layer to remove the background, so, again choose a new layer from the bottom of the palette. Since we are working on a high-key image, I want the background to be white. Choose the colour white, select the brush tool and select a large soft brush with a faded edge to work with.
All you have to do now is to work carefully around the edges of the image with the brush to paint white over the image. As this is a new layer, we are not doing any damage to the layers underneath. If you make a mistake, then simply elect the eraser and remove the offending white section. There are other ways to remove the background, like masking, but I wanted to keep it simple ;)
Once you have removed all the distracting background you are left with a very nice high-key image to look at. You can now dodge or burn areas of the image for final touches. I like to burn the eyes a little to make them stand out.
Once you do this a couple of times, you can quickly do this process in 5 to 10 mins, maybe longer for printable work. Usually, for high -key to be done correctly, it should be done in camera, but this can and does work well for certain images. Here are a couple of other examples, as you can see the backgrounds are different but you can still get a nice effect.
If you have any questions or comments, then feel welcome to post them in this thread.