Deke’s Techniques: How to create an optical illusion

Published by | Tuesday, January 15th, 2013

In this week’s Deke’s Techniques video, Deke McClelland takes an Adobe Photoshop journey into the eye-bending world of op art, creating a ’60s-inspired twist and bulge of checkerboard contortion. You won’t need a sample file or unsuspecting model to follow along with this one—just Photoshop, some black and white pixels, and a love of (and visual tolerance for) optical illusion.

The project starts with a simple square document, created in the Grayscale color mode to keep the high-resolution file manageable. (You won’t need any colors, so no sense making room for them.)

How to create an optical illusion in Photoshop

Next, Deke creates a 2 x 2 checker pattern by using the Rectangular Marquee tool set to a fixed size that’s equal to one-quarter of the total image. Once the upper-left square is filled with black, you can drag a copy to the lower-right corner by pressing the Alt (Option) key while you drag.

Create the pattern in Photoshop

With the basic unit of the pattern complete, you can turn it into a reusable Photoshop pattern by choosing Edit > Define Pattern. In this case, Deke aptly named it Checkers:

Name the pattern for the Photoshop effect

Deke then applies the Checkers pattern to a new blank 4800 x 3000 document. Click the black/white icon at the bottom of the Layers panel to make a new Adjustment Layer and choose Pattern. Then choose your Checkers pattern from the available patterns and set it to 50 percent to fill the document with small squares.

Create the pattern in Photoshop

Saving the pattern layer as a Smart Object allows you to warp it nondestructively with the Transform command. Choose the Warp icon from the options bar and set it to Inflate from the Warp pop-up menu. Then set the Bend to -100. The checkerboard is pinched inward:

Warp the image in Photoshop

The pinching motion of the Inflate transformation has pulled the pattern away from the edges. Deke adds more checkers to the outer edges by opening the Smart Object and doubling its size.

Example of the pinching motion of the Inflate transformation.

Deke then creates the round, prominent part of the illusion by applying the Spherize filter to a circle selection in the middle of the image.

Apply the Spherize command

To achieve the final effect, Deke applies two more doses of the Spherize filter, and the result is a swirling, bulging, some might say hypnotizing bit of Photoshop-created op art.

The final image

For lynda.com members, Deke’s got another exclusive video called Op art experiment 1b: Rounded Windows, in which he turns a flat collection of rectangles into a curving wall of optical mystery.

Deke will be back next week with another mind-bending technique.

Suggested courses to watch next:

• The entire Deke’s Techniques collection
• Photoshop CS6 One-on-One: Intermediate
• Illustrator CS6 One-on-One: Intermediate

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