Ok, there seems to be some interest in this, so instead of writing to everyone that asked me "how to do it", I'd be better off writing it once and referring people to this thread.
What we're talking about here is a pretty basic concept, to put an item in color surrounded by a B&W picture. For an example of what I'm talking about, see Steve aka Nelson's thread.
To obtain this effect, open the image in Photoshop, create two copies of the background layer. To do so, open the "Layers" window (Menu: "Window > Layers", or press F7), take the small icon labeled "background" and drag it at the bottom of the Layers window on top of the icon that looks like a block note with the first page half folded. This will create a copy of your layer. Do this twice.
Next, select the top most layer, probably labeled "Background copy 2" by now. You need to transform this layer in B&W. To do so, follow the "transforming pictures in B&W channel mixer" article by Pierre Daniel posted on Phototakers, and then come back here for the next step.
Now you should have the top layer in B&W, the second layer in color, and the background also in color. You don't actually need the background, but I like to do things this way because it allows me to check with the original file anytime I need to. What we will do is make the background invisible, so in the Layers window click on the eye-shaped icon beside the layer "Background". Nothing dramatic will happen as this layer is under two other layers anyway, but we'll use this feature at the end of this procedure. For now, simply make sure that the background is invisible, while the two top most layers are visible (i.e. the eye-shaped icon is visible on these layers).
Ok, now comes the interesting part. What you want to do is create a mask into your top most (B&W) layer. A mask is an easy enough concept: when the mask is painted in white, the layer is visible, when it is painted in black, it's invisible, and when it is painted in any shade of grey, it will be semi transparent (in relation to the amount of black in your gray). So select the top most layer (the one in B&W) in your Layers window, and click on the small icon that looks like a grey square with a white circle in the middle, i.e. the second icon from the left at the bottom of the Layers window. This create a mask in your layer.
Now, make sure that you are working in the mask by clicking the white square that just appeared in your currently selected layer. This is important to remember: if you have a mask in a layer, you have to make sure that you select the right icon. The picture icon on the left represents the actual picture in the layer, while the white square is the mask. If you don't select the mask but instead start working on the picture, you will paint your picture in white or black, which is not what we want. Conversely, if you select the mask and try to adjust contrast, saturation, or pretty much anything, it won't work and you will wonder what goes wrong.
Once you are sure that the mask is selected, select a brush with a size you are comfortable working with (press "b" on your keyboard or select it from the tools window), select black as the foreground color in your tool window (you can press "x" on your keyboard to switch between black and white), and start drawing around and in the object that you want to appear in color in your B&W picture. By painting the mask in black, you effectively render this portion of the B&W image transparent, thus unmasking the colored image in the layer below. If at any time you make a mistake and want the B&W to appear again, switch to white, and paint this portion of the mask in white again. Voilà!
Once you are done and totally happy with the result, you want to merge the visible layers by going to the Layers menu and select "merge visible". Alternatively, you can press "command-shift-E" on a Mac or "control-shift-E" on a PC. This "flattens" the image into only two layers, the B&W and color composite, and the background. That's why I asked you to make the background invisible, so it would still be there after this last step. Now, make your background visible again (click the empty icon to make the eye appear), and you can compare the original with your artwork by making the top most layer invisible simply by clicking on the eye icon. If you're happy, you may decide to flatten this again to save disk space or not, up to you!
About the Author:
Cédric John was born in Switzerland, where he grew up before moving to Germany to pursue his studies. After graduating with a Ph.D. degree in Earth Sciences at the University of Potsdam, he moved to California where he currently works as an academic researcher. Cédric’s interest in photography started in 1997 with the acquisition of a Canon EOS 5 SLR camera, but was seriously boosted with the advent of affordable digital SLR cameras. His main photographic interest is nature, from macro to landscape, including wildlife photography.
