We live in a world that is defined by three dimensions: width, height and depth. We consider the fact that the world is three-dimensional quite obvious and natural. It is one of the basic principles of our perception of the world.
The era of photography has begun in the 19th century when the first technique to record the image appeared. With the exception of a handful of remote corners of the world where civilization has not yet arrived, there almost isn't a person who wouldn't know what a photograph is. Millions of people can view photos, but they can also buy them. A huge boom in photography has come with the advent of digital cameras and, especially, of modern cellphones.
Few people realize the fundamental contradiction between photos and the real world: in comparison to reality, photography is merely two-dimensional, flat. It lacks the depth of space. We've got used to this fact to such an extent that we consider it completely normal. When looking at a photo, we estimate which objects are situated in the foreground and which ones are in the background. The idea of the depth of space is created in one of our brain centers based on life experience. Therefore, it is not real, it is only imaginary. We do not see the real depth of the image. It can't be seen because it is not even captured in the photo.
In many cases, this creates a jumble of shapes and colors which makes it nearly impossible for us to distinguish what is close and what is further away. These images lack the third dimension, the depth of space, to such an extent that they are opaque and thus unattractive. Their documentary value is low.
All objects in the flat picture - in short, long and medium distance - are projected onto a single plane. Why is it so? This causes a fundamental contradiction between our eye and the lens of the camera. Us people are watching the world with two eyes while the camera only has one lens, a sort of one eye. Try to cover one of your eyes and observe your surroundings with the remaining one. When you do that, your perception of the world is deprived of a lot of information, and it is completely different from your everyday life experience.
If you want to see the real world recorded on the photograph in all its beauty and in the exact way we perceive it with our eyes, it is possible only by means of a three-dimensional photograph.
Formerly, it was called stereoscopic, now we use the term 3D, i.e. three-dimensional. Stereoscopic photographs in the form of slides were one of the fruits of Hanzelka's and Zikmund's travels around the world.
Whether the image showing all three dimensions of our world is called spatial, three-dimensional, stereoscopic, or 3D, it has one important feature - almost no one knows it exists. This can be considered to be one of the greatest paradoxes of the modern world. The technology of the 21st century is capable of almost anything. Humanity is flooded by various gadgets and amenities. The full-fledged three-dimensional view of the world through the 3D picture is, however, almost unknown to mankind.