It is a knack, not a talent. Most people who think they cannot see stereograms simply have not been shown how, and get there within a few minutes. This trainer starts with two dots and works up.
Look at the two dots below, then let your eyes drift as if you were staring at something far behind the screen. When it works you will see three dots instead of two, and the middle one will look sharper. Move the slider until that happens easily.
Narrower is easier to start with. Once you can hold it, widen it - wider spacing means a bigger, more dramatic hidden image.
A stereogram works by asking your two eyes to line up on points a fixed distance apart. That distance is physical - centimetres on the glass - not a number of pixels. Shrink the image to fit a window and you change it, which is why so many stereograms on the web simply do not work. On a computer we show them at actual size and let you scroll. A phone held at arm’s length gets the picture fitted to its width, which there comes out at about the same size anyway.
There are two ways to do it: let your eyes drift apart (parallel, the classic way) or cross them. Both work, but they produce opposite depth - an image made for parallel viewing looks carved in to a cross-eyed viewer. If everything looks inside-out, flip the switch in the studio rather than fighting it.
About 1 in 14 adults cannot fuse a stereogram at all, most often because of amblyopia, strabismus or another difference in how the two eyes work together. Nothing in this guide will change that, and no amount of trying is going to help. That is exactly why every image we make ships with a Reveal.