We regret to inform you that we cannot accept your submission for addition to the iStockphoto library for the following reasons: iStock does not accept overly simple auto-traces. Files tend to simplify complex areas, create rough outlines that limit a file's usefulness, leave white gaps between your shapes, and can add a lot of extra points to your file that aren't necessary.

Auto-trace. So powerful. So fun. So misused. Yes, it seems almost too good to be true — "Turn your photos into vectors!" — and well, it is. Don't get me wrong, "Live Trace" (as it's known in Illustrator) is an amazing technology. But with great power comes great responsibility — you must wield it with care.

The reason iStock doesn't like auto-trace so much is explained above. If you try to trace a continuous-tone photo with the click of a button, the results tend to be bad. Really bad. On the left is a photograph, on the right is a high-fidelity Live Trace.

It looks pretty good at its original size, but zoom in and you start to get the big picture. The big, ugly picture. Take a look at the outlines and the points, and you'll flip your wig. The photo is only 500 x 700 pixels, but the trace contains a whopping 4855 paths, 31,438 points and 50 colors!

Left: Photograph

Right: Auto-trace

Below: A hot mess

After the trace is "expanded," that is, committed to vector and no longer "live," you can see miniscule white gaps between the shapes. This could jeopardize your relationship with your printer.

And really, what's the point? We've got more than seven million photos on iStock. A simple — yet overly complex — auto-trace doesn't really add anything to the oeuvre.

Of course you CAN use auto-trace, you just have to use it for the right things. Silhouettes lend themselves quite nicely to Live Trace, but require some manual cleanup. Grunge frames and backgrounds, some of the most popular vector files on iStock, are created with the aid of Live Trace. Notice I said, "with the aid of." Some human intervention is always needed to make the cut as stock. Otherwise, everybody would be doing it.

A Quick How-To

Let's take a quick tour of Illustrator's Live Trace. We'll start with an easy way to make a vector silhouette. This is meant as an introduction, not a comprehensive tutorial.

First, select a photo. An object isolated on white works well. Place the photo in Illustrator (File>Place). The Control Panel will display a Live Trace button and a drop-down menu of presets. These presets are only starting points, and their names are just suggestions. You can test each preset without committing to anything right away. That's why it's called a "live" effect.

For this leaf, the "Comic Art" setting produces the best initial result. After the trace is completed, you can preview the paths by clicking the buttons in the Control Panel. This simply gives you choices of how to view the trace on screen. For example, you may want to see the paths in outline mode, to check them against the raster image before committing to the trace. It doesn't affect the Trace Settings at all. That's the "live" part again.

You can see that the stem of the leaf has some extra points, so adjust the Threshold. A little bit higher is just enough to smooth out the stem, but the leaf edges remain jagged.

More comprehensive adjustments can be performed in the Tracing Options dialog box, which is accessed via the Object menu, or from the little proxy on the Control Panel. Since we want just the shape of the leaf and not the white background, check "Ignore White".

When everything looks good, click the Expand button (or go to Object>Live Trace>Expand), to turn the trace into vector elements.

Zoom in and closely examine the paths. Make necessary refinements with the Pen tools, the Eraser and/or the Smooth tool.

Do's and Don'ts

  • Don't rely on any "out of the box" settings. Get to know the presets, sure, but experimentation is key. Try as many possible combinations as you can in the Tracing Options box. And even with carefully adjusted settings, be prepared to tweak and smooth the paths of your final trace.

  • Do try tracing something that's not a photo, like the paint splatter below. Live Trace is great for sketches and texture. Use it to achieve effects that would be nearly impossible to draw by hand. The result is the best of both worlds — the realism of a photo and the flexibility of a vector.

  • Do simplify your paths, using Object>Path>Simplify. A high Curve Precision setting (90% plus) will maintain the shape, but drastically reduce the number of points

  • Don't forget to check for open paths after you've simplified the trace.

  • Do download this reference guide to all the Live Trace presets.

  • Do have fun!
Photo of splattered paint
Live trace

Image credits:

New Shoes by stalman
Surprised Nerd by ferrantraite
Maple leaf by Razvan

Cheryl Graham (FreeTransform) began uploading to iStock in December 2005. She creates Adobe® Illustrator® tutorials for the Layers magazine Web site, as well as her own blog, freetransform.net.