An ancient steep stone stairway that leads up to the sunlit world:

A dungeon? A sewer? A tomb? Beats me. It was a stock photo by Polish photographer Michal Adamczyk, but that's all I know about it. I converted it to 3-D anaglyph with Photoshop using a depth map. There is a very cool atmosphere to it, don't you think?

Pretty as a picture:

After you've done a few depth maps, you start to acquire an eye for the sort of image that would make an ideal subject for a 2D-to-3D conversion. This photograph of a woman in a white skirt and gloves (a stock photo by Lev Dolgachov) was such an image. A beautiful model, and an interesting composition, that would become even more interesting as a 3-D anaglyph.

The background and gloves were originally red. Before doing the conversion, I changed those to gold, in Photoshop. I've learned that strong red shades do not benefit from the anaglyph process, and it's best to avoid problems like that before starting.

I am told that there is anaglyph-making software that will automatically turn reds into yellows, but I would not trust this beauty to some global color adjustment; I would worry that the rosy hues of her hair and skin would become jaundiced. So I re-colored the gloves and floor by hand.

I do usually get my stock photos from iStockphoto, but this month I'm using Crestock, just because they give a killer introductory discount for signing up there. Their selection isn't as good as iStockphoto's, but they do have many good images, and at fifty percent off, well, they're worth the money. Oh, and Crestock has a free stock photo every day, whereas iStockphoto only has a free one every week. I always download the free images from both sites, even if I have no present use for them.

If Club Penguin really existed in three dimensions, it might look something like this:

(There is an even bigger version of this 3D picture, here.)

Disney's Club Penguin is an online virtual world where everyone is a penguin. This 3D view is based on the Club Penguin home page. I'm not exactly a fan, but my daughters are, and I made this especially for them.

I made the 3D image by making a depth map, and using it as a displacement map on the flat picture in Photoshop.

Starting with the famous John Trumbull painting of the signing of the Declaration of Independence, I turned it (or a detail from it, anyway) into a 3D anaglyph by using a "depth map" as a displacement map in Photoshop.

The "depth map" is a separate file the same size as the flat image, with various shades of gray to indicate the depth of every part of the image. White is closest, black is farthest. Using this as a displacement map in Photoshop on the flat image -- with a negative X offset for the red channel and a positive X offset for the green and blue channels -- turns it into a 3D anaglyph.

When I made the header art for this site, I knew just the photograph I wanted: an attractive woman wearing red-and-blue glasses, looking at the logo, expressing both surprise and happiness. And the photo had to be in 3-D. As you can see at the top of this page, I got just what I wanted. But I didn't find what I wanted; I had to make it.

Here's what I found: a stock photograph by Sharon Dominick, on iStockphoto.com. (And by the way, if you're not buying your stock photos from iStockphoto, you are wasting money. Go sign up with iStockphoto, or you're fired.)

I could tell right away that -- besides facing the wrong way, and looking in the wrong direction, and not wearing 3-D glasses, and having hair blowing everywhere, and being only two-dimensional -- this girl was perfect. Simply perfect. Well, she wasn't quite happy enough, either. But perfect besides that. So I bought the photo.

To fix the parts that wouldn't work with my layout, I retouched the photo. I flipped the image so she faced leftwards, erased some of her hair, blacked out the lenses of the glasses, cloned out her shoulder strap, and pulled her mouth ever-so-slightly into a happier smile.

That was the easy part. But she still wasn't in 3-D. Usually, you make a 3D photo by using two separate images shot from slightly different angles. But how do you make a 3D photo from a single flat image?

I did it by making a layered Photoshop file. Each layer contained just a little less of the image than the one below it. The bottom layer had the whole portrait; the next layer, just the head; the next layer, the chin and face; and so on, until the top layer just had her nose and glasses.

The trick here is to feather the edges of your eraser just right. If you use hard edges everywhere, the edges of your layers will show up in the 3D image, and make her look like she's made of construction paper. In most places, you want to use feathered edges to make smooth transitions from one layer to the next. But in some places, you want a hard edge, for a sharp transition (such as where her glasses appear in front of her hair).

After that, I made a copy of every layer so I had two full sets. I colored one of these sets red and the other cyan, and moved the layers to simulate the two different viewing angles. Merging them into one anaglyph image gives me this:

For my header art, I colored her lenses blue and red, but I reckon I'll leave them black here. She looks pretty cool.

No matter how hard you work at it, you'll never turn it into a true stereoscopic photo. But you can come pretty close, probably close enough to fool most people, especially if you plan to use it at a smaller size, such as in my header.