Projected Shadows Tutorial Author - Man1c M0g (http://forums.biorust.com/member.php?userid=1)

The art of effective photography is making excellent use of your surroundings.  Shadows cast by relatively simple nearby objects can greatly enhance your images, adding moody atmospheric lighting and suspenseful themes.   Of course, obtaining a good shot of a shadow interacting with your subject can be difficult, especially considering that you can cast shadows too, making interference a very real and annoying issue.  But why spend hours frustrated by nature's own little lighting problems when you can simply take any shot you like and add your shadows later?   Its tremendously simple and, best of all, offers superb levels of flexibility.  Just what your psychiatrist ordered!  ;) 
 

Step 1: Open up a stock image in Photoshop of any size and/or format. If you have a darkly-colored source image you may want to spend a few minutes playing with the contrast/brightness or levels to improve the overall color clarity and give it the appearance of being taken in sunlight -  After all, it will look more than a little odd to have a strong shadow in an overcast scene. Please note that the image to my right was grabbed from the excellent SXC.HU archive - where there are good source images on almost any subject.

Step 2:  Open up an image containing the object you intend to use as a shadow.  There is no need for this source image to be wonderfully detailed, but it must have a resolution similar to your other image, and have good color separation.  For my example I have chosen a picture of a houseplant with long spear-like leaves. Now all you have to do is form a new selection around the object of your choice that excludes it from the background.  In my image below I was able to use Select > Color Range with the Select listbox restricted to Shadows.   Your image may be different, but I have found that color range selection usually gets the best results.  If you need a tutorial on this subject you can find one here. Once you have formed a selection around your object you need to save it and then export it to your first image.  I find that the best way to do this is to save as an alpha channel.   To do this, just navigate over to the channels palette WITHOUT losing your selection and click on the 'Make new channel from selection' button ( ) at the bottom of the palette to form a new alpha mask.  When you have done this, click and drag the alpha mask from your object image over to your source image to copy it over.   You can now close your object image if you want - we have no further need for it.

Step 3: You will now have a new alpha channel in your first image.  Hold down ALT (Mac:  OPT) on your keyboard and click on the alpha mask to reform your selection, and Select > Feather it by 2px (5px if you have an especially large image).  Back in the layers palette, create a new layer called Shadow, make it active in the layers palette, Edit > Fill with 50% grey, and deselect.  Change the layer blending mode to Multiply and the opacity to 75% to give yourself a shadow. This shadow is basic and functional, but blatantly artificial as real light would contour itself to the shape of the material underneath it.  This problem, however, is very easy to correct with a little creative use of filters.

Step 4: Hide your Shadow layer and save your document.  It does not matter what you call it or where you place the .PSD file, but the shadow layer *MUST* be hidden.  When done, make your Shadow layer visible once more and ensure it is selected in the layers palette.  Run the Filter > Distort > Displace filter with the settings as shown on the left.  Once you press OK you will be presented with a second dialog box asking for a source - select the .PSD image you just saved and press OK.

Step 5: After a little processing time you will be left with a brand new Shadow layer that conforms to the underlying material... just like a real shadow!     This shadow works well, but we can still see the shadow pouring over past the woman and onto the background under the hammock, which is some distance away.  A real shadow wouldn't be cast this way, so bring out the eraser tool and delete the erroneous shadow elements wherever they lie. This shadow is much better, but real shadows exhibit light diffusion, meaning that they are much darker at their base than at their ends. Thankfully, however, this problem is remarkably easy to correct with a little layer effects magic!

Step 6: With solid white selected as your foreground color and your Shadows layer active in your layers palette, select Layer > Layer Effects > Gradient Overlay from the main menu.  Duplicate the settings in the image opposite and press OK.

Step 7: And you're done!    Of course, the beauty of this technique is that it is non-destructive to the original source images.  If you are so inclined you can easy add adjustment layers later to manage the color a little better, or even overlay multiple object shadows to create more complex scenes.  Anything is possible with a little imagination! NB.   To compare before & after images, just place your mouse over the image to the left.  You'd never figure out that the shadow is totally artificial!