Friday, March 31, 2006

Depth of Field

An original Photoshop® Tutorial

Requires Adobe Photoshop CS or later. An intermediate skill level is recommended, and you should be comfortable with making detailed selections. If you need more guidance for making the selections in this tutorial, please review my original DOF tutorial. To follow along, download the image below:
downlaod file download file
This tutorial provides an introduction to using the Lens Blur Filter, a tool added to Photoshop CS (version 8.0). If you have an earlier version of Photoshop, please see my earlier DOF tutorial, written prior to the release of Photoshop CS.

Download a larger version of this image.
[Source images provided by Digital Photography Review.]

In Search of the Gradual Blur

Many digital cameras tend to have little or no control over depth of field, leading the photographer to enlist the help of Photoshop to achieve variations on this effect. The goal of this tutorial is to manipulate a photograph into simulating a shallow DOF exposure, a technique typically controlled on manual cameras by setting a larger aperture (e.g. f/2).
The problem that I have seen with other tutorials on the same subject is that they tend to simply blur the background of the photograph. Sometimes, this may be all that is needed; however, a background tends to contain much more depth (i.e. objects vary in distance from the subject). A true representation of shallow DOF would show a gradual blur, with the blur becoming more intense for objects that are farther away.

Paint That Channel

In the Channels palette, create a new channel (Alpha 1) and make all channels visible by clicking on the channel visibility next to RGB (the eye icon should appear for all channels). Be sure that the new Alpha 1 channel is still selected.
Set your default colors (D), select the Radial Gradient Tool Radial Gradient Tool, and drag in the direction of the arrow indicated in the image above.
Make a selection around the back card and its coaster, fill your selection with #EEEEEE, then deselect.
Make a selection around the middle card and its coaster (it's okay to over-select on the left side), fill your selection with 50% Gray, then deselect.
Make a selection around the front card and its coaster, fill your selection with Black, then deselect.
If you toggle off the visibility indicator in the RGB channels, your Alpha 1 channel should look like the image above. Before moving onto the next step, toggle on the visibility for the RGB channels and turn off the visibility for the Alpha 1 channel.

Next Stop: Lens Blur

Go to the layers palette and select the Background layer, then duplicate this layer (Ctrl+J on PC or Command+J on Mac) and name your duplicate layer DOF.
With the DOF layer selected, go to Filter > Blur > Lens Blur... and use the settings from the image above.


The image should now resemble my own, at the bottom of this page. Compare your result to the true DOF photograph at the top.
This is intended to be a simple introduction to a very powerful tool, the relatively new Lens Blur Filter. Use it as a launch pad for experimenting further, to see and understand how each setting affects the image.