How-To: Deploy Smart Stacks in Photoshop CS3 Extended

This step-by-step tutorial teaches you how to erase moving objects from crowded street scenes with a new feature in Photoshop CS3 Extended. Plus, a workaround for those not ready to shell out big bucks for the new software.



Ever wanted to capture a pristine photograph of a fountain in Rome or bridge in Paris, only to be eternally frustrated by tourists who keep walking through your frame?

With the new Smart Stacks feature in Adobe Photoshop CS3 Extended ($999 new or $349 upgrade), it's now easier than ever to make a street scene free of people, even if you don't have the place all to yourself!

We've just begun learning how to use Smart Stacks to its full potential. It's the long-sought "tourist eraser" filter that many photographers have been asking for. (We've even heard it referred to as the "Neutron Bomb filter" by the less PC crowd.)

The concept of Smart Stacks is to expose multiple frames of an identical scene at the same exposure and combine the layers so that the static elements remain after layer-masking out the moving elements. What you're left with is a landscape or cityscape minus any people.

Normally this requires a ton of work -- as we'll demonstrate for those who want the "Tourist Eraser" effect but don't have CS3 Extended. Using Smart Stacks, however, is significantly faster -- a couple of keystrokes and mouseclicks and you're done!

(In our example, we're dealing with only a few frames and a handful of moving elements, so the manual method might not seem like that much work. But imagine this isn't a simple sidewalk and wall, but St. Mark's Square in Venice, or Washington Square Park in Manhattan with hundreds, if not thousands, of moving elements in the scene and 30 or 40 source images!)

In either case, Smart Stacks is not absolutely perfect all the time, and it works best when a moving object completely vacates the previous pixel locations between frames and no other moving element occupies those recently vacated pixel spaces. Otherwise, you'll get weird semi-deghosted artifacts in the final combined image. We shot 13 frames of this street scene and had to try a few different four-image combinations to get it seamless. It took us three tries to get it perfect. As you've heard me say more times than I can count, experimentation is a big part of the process with multiple-source imaging.

Smart Stacks "Tourist Eraser" Tutorial
Manual "Tourist Eraser" Tutorial

Check back in mid-June when we show you how to use Smart Stacks for High Dynamic Range Imaging.