Casting Realistic Shadows

To start find a picture you would like to add a shadow too. For this tutorial I will be using this picture:

Now take your render layer and duplicate it by dragging it over the New Layer button. Now your layer's palette should look like this:

Now take your copy layer go to Image > Adjustments > Hue/Saturation, or just press Ctrl- Hue. Then set the Lightness on -100. Now you picture should look like this:

Now go to Edit > Transform > Distort. And take the top middle dot and drag it down like so:

Now your shadow should look something like this:

So now we have our basic shadow. But it's time to edit it to make it look realistic. Go to Filter > Blur > Gaussian Blur. Use these settings:

Now go to your layers palette and lower the opacity of your layer anywhere between 85% - 95%. Just see what looks best for you. I used 91%.

Now go to layers palette again and add a quick mask to your shadow layer. Then apply this gradient to it.

Click to enlarge

Now you have your gradient settings lined up so take your gradient click and drag it like this:

Now if you applied the gradient correctly you should have something like this:

And congratulations! You have finished my tutorial on how to cast a shadow! Now you can create shadows on anything. Enjoy!