• Producing a Hologram
• Types of Lasers
• Still Holograms v. Stereograms

Holography 101

Although often compared with photography, holography is really a completely different medium.

Holography is based on different optical principles than photography and holograms have different physical attributes than photographs. They are comparable only because both are ways of recording an image onto a piece of photosensitive material (film) and because, at times, similar equipment and materials are used.

Traditional Pictures Have No 'Depth'
The most obvious difference between a hologram and a photograph is image depth or image dimension. When we look at a photograph and move it from side to side, we are unable to see ‘around' the scene or perceive any depth. Likewise, we cannot see over or under the image. We see only a flat (two-dimensional) picture displayed on the surface of the film. The picture is actually only a collection of light and dark areas that we recognize as a particular subject. Our memory might remind us that the subject really has dimension and depth, but such visual information is not recorded in the photograph.

Multiple Views Create '3D Effect'
A hologram is also flat, but the image captured by the hologram is not. When we look at a hologram and move it from side to side, we can see many different views of the scene. We can also look behind foreground elements to see things in the background. This property is called parallax, ‘the apparent displacement of an observed object due to the difference between two points of view.' Each of our eyes sees a slightly different image, and our brain processes these multiple views to create image depth so that we perceive a three-dimensional image. A hologram displays many views of the same object so that we see a three-dimensional image with depth, whereas a photograph is limited to only one view, resulting in a flat, two-dimensional image.

Holograms Appear to 'Leap Off' the Film
Another difference between holograms and photographs is that holographers can position their images to ‘project off' or ‘float over' the surface of the film. A viewer can reach out and put his hand right through the apparently solid image. The holographic image can also be positioned to appear some distance ‘behind' the picture frame. Others straddle the surface of the film. Well made holograms can appear to ‘leap' from their frames, and certainly appear real enough to reach out and touch. No photograph can do that!

Want to learn more about holography, and how LitiGraphs are produced? Read more in the other Technology sections we've prepared: Producing a Hologram, Types of Lasers, Still Holograms v. Stereograms.

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