Introduction

A photograph can be very beautiful but is always limited to projecting a view onto a two-dimensional plane (the film/photo). Stereo photography is a technique to make two photographs of the same subject, from slightly different positions. For normal close, small objects, the two positions should differ approximately by the human eye distance (about 10cm or 4").

Weather photography is no difference, and in fact you can create remarkable three-dimensional pictures by exaggerating the distance of photography locations. Because most subjects of the weather are relatively far away (several kilometers for a cloudy sky, for instance), increasing the distance creates very clear three-dimensional pictures.

This stereo pair shows a cumulus sky from an airplane, which is ideal for stereo photography.

How to do stereo photography

The technique is very simple - as outlined in the introduction above. Care must be taken to photograph the same sky with exactly the same settings and do the two exposures as soon as possible after eachother, in order to photograph the sky statically.

You can try this technique with any subject you want. Here are a few guidelines:

• By increasing or decreasing the distance between photography locations, you control the 3D-depth of the stereo pair of photos

• For subjects farther away, increase the distance between photography locations. This can be several meters already if you photograph a cumulus cloud, for instance.

• For transient subjects like lightning, you need two separate cameras a distance apart from eachother, which take a picture simultaneously.

• If you are in an airplane, you do not need to move the camera between the two photos, because the plane is already moving. Just take two pictures quickly after eachother (with typically less than one second in between).

• Things like halos, rainbows, heiligenschein etc. do well also for stereo photography. You will notice that the light will seem to come from behind the cloud/raindrops rather than from within: this is because most of these optical effects are fixed to the position of your eye rather than the position of the object in which they occur.

This pair of photos was taken from an airplane, with appreciable time between the exposures (more than one second). As a result, the 3D-picture shows excessive depth. However, the cumulonimbus clouds are excellent subjects to view in stereo. A single photograph just cannot catch the same as you see with your own eyes in nature.

An interesting thing to try: when you get the 3D-picture in view, try to touch with your hand one of the clouds which you are seeing in the stereo photos above. You will notice that your hand will reach for something in front of the computer monitor, because your brains think that the cloud is closer than the screen.

Order is important!

Make sure that you note down the order in which you photograph the pair. The right photo should end up on the right, or the three-dimensionality will be depth-inverted (which looks really strange).

If you are flying in an airplane, you have to note down in which direction you were taking the pictures and in which direction the aircraft was flying; then figure out which of the two photos is which. I can help you with this: if you are sitting on portside (left side) of the plane, and photographing to that side, the first photo is the left photo. If you are sitting on starboardside (right side), the first photo is the right photo.

Needless to say, you should book a window seat when you fly, or check in early and ask for one.

Viewing stereo photo pairs

This requires some practice, but after this, anyone should be able to view stereo photos. The idea is that the pair of photos should be separated by approximately the same distance as that of your two eyes. Then, you have to look to infinity, while accommodating your eyes on the close pair of photos. The accommodation you will do automatically, but this is an unusual state of your eyes (usually when your eyes focus to infinity, they also accommodate to infinity), and you may develop a slight headache.

Focusing to infinity while accommodating to a nearby photo is what you have to practice. Do this by identifying two objects in both photos which are the same. Then gradually relax your focus. Do not keep focusing on the pictures. You will notice that the two objects which you were looking at, seem to merge together. They should merge over eachother, and not have a top/bottom asymmetry (if there is, tilt your head until they are on the same line). As soon as they merge, keep your focus, try to look at something in the photo which you know is almost at infinity, wait a few seconds, and the full 3D picture will come into view. If you are unable to get the 3D-picture, try the method while sitting closer to or further away from the photo.

This stereo pair of photos is difficult to view. The cloud bow is at infinity (since it is a reflection of sunlight), while the clouds have moved appreciably. It is hard to maintain the 3D picture once you get it, but it is worth the try. You will notice that the cloud bow (which is caused by the same mechanism as the ordinary rainbow) is not an object in the cloud, and that the cloud bow does not seem to be more close or more distant anywhere in the picture, while the cloud deck is closer at bottom.