Photo Realistic Drop Shadows in Photoshop

Step 4: Apply The Gaussian Blur Filter To The New Channel

We're going to be using this new channel as our displacement map for our drop shadow, and one of the things we want to avoid is having any harsh or rough edges in the displacement map so that our shadow will flow smoothly and naturally with the ripples and waves in the water. To make sure everything is nice and smooth, I'm going to add a Gaussian Blur filter to this channel.

With the "Alpha 1" channel selected, go up to the Filter menu at the top of the screen, choose Blur, and then choose Gaussian Blur, which brings up the Gaussian Blur dialog box:

Photoshop tutorial: Select Filter > Blur > Gaussian Blur to bring up the Gaussian Blur dialog box.

You want to add just a slight amount of blurring here. I'm using a low-resolution image for this tutorial, and for me, a Radius value of about 2 pixels does the trick. If you're using an image straight out of your digital camera, chances are it will be much higher resolution, and in that case, you'll probably find that a setting of around 5-6 pixels works well. Again, we only want a slight amount of blurring, just enough to smooth everything out.

Step 5: Boost The Contrast Of The Channel With Levels

The next thing we want to do is boost the contrast of this channel, since the higher the contrast, the more of an impact our displacement map will have. Again with the new channel still selected, use the keyboard shortcut Ctrl+L (Win) / Command+L (Mac) to bring up the Levels dialog box:

With the Levels dialog box open, drag the black point and white point Input Levels sliders (both circled in red above) in towards the center to boost the contrast of the channel. Don't worry about losing any detail in the highlights and shadows as you would if we were using Levels for a tonal correction on an image. Here, all we're concerned about is boosting the contrast.

Here's what my channel looks like now after increasing the contrast with Levels:

We're done working on the channel and it's ready to be used as a displacement map, but to use it, we have to create a new document out of it, and we'll do that next.