Introduction: Creating Depth of Field

In this tutorial we will learn how to take a picture that is in focus and alter it to create a greater illusion of depth and use it to direct the user to focus on the desired area of the image.

1. Learning About DoF

First we need to understand what depth of field is, if you look anywhere on the web you will find the following description to what depth of field is:

From Wikipedia: "Depth of field is the distance in front of and behind the subject which appears to be in focus. For any given lens setting, there is only one distance at which a subject is in focus, but focus falls off gradually on either side of that distance, so there is a region in which the blurring is tolerable."

So, explained another way: Depth of Field is an effect defined by the perceptible level of sharpness of an image according to the relative distance of all of its parts. A shallow depth of field would make your area of focus smaller while blurring everything else in front and behind the focus point. Conversely a large depth of field cause the focus area to be broad therefore making more of the image to appear sharp and in focus. For this tutorial we will attempt to create the illusion of a shallow depth of field to an image that is fully in focus.

Ok, knowing this we will attempt to take a picture with a relatively even depth of field and alter it to give the impression of greater distance as well as focusing the attention on the sharper sections of the image.

There are different ways to achieving this effect, but in essence the process is very similar although its application can be different based on the image.

2. Preparing the Subject

Now, everything within this photograph is relatively in focus:

We are going to use our little trick here to draw the attention to a specific point on the image. Press CTRL + J on your keyboard to duplicate the layer via copy. We are now ready to create a cut out of our bridge using the pen tool, magic wand or whatever method you feel is more adequate or you are more comfortable with:

3. Preparing the Background

Now that we have our cut out of the bridge we are ready to begin adjusting our image to create a more dramatic depth of field. In this image our background seems to be running almost perpendicular to the bridge so we have to prepare our background layer and our bridge layer to have a lens blur properly applied. With the background layer selected go to your Channels palette and create a new channel. This will create a new alpha channel on solid black.

Now using a 50% black and using the gradient tool, paint the gradient from left to right in the alpha channel. We will use this channel in our Lens blur later.

4. Preparing the Foreground

Now let's move on to our bridge layer to prepare it for the Lens Blur as well. Since our cut out of the bridge is done with a mask, our bridge layer shows the mask as a new channel. Duplicate the mask and invert the new channel.

While holding the CTRL key, mouse click on the channel to select the solid part then CTRL + SHIFT + I to select inverse. Once selected we will go back to our gradient tool, and reset our gradient swatch by clicking the little black and white square on the bottom left of the swatches. Draw a gradient from white to black, with black being closer to the foreground.

5. Applying the Lens Blur

Ok now we are ready to apply our lens blur. Select the background layer and go to Filter> Blur> Lens Blur. I used the following settings, but feel free to experiment and find the numbers that feel right to you, then press ok.

Now we can work on the Lens Blur for our bridge layer. go to Filter>Blur>Lens Blur. For the Source we are now going to use the "Layer 1 Mask copy" channel. Here are my settings:

6. Conclusion

Now we have our final image with an overly dramatic depth of field, all thanks to photoshop. This is of course one way to do this in Photoshop, and there are other methods that can be used to accomplish the same thing. You should explore different settings and similar concepts to find a process that is best suited for your needs.

The effects here are greatly exaggerated but with a more subtle approach a more realistic feel can be achieved. Compare the images below to see the difference.