How do videos work?

Actually, you have to go back to ‘ancient’ history to understand how video (moving pictures) work.

The proper term for videos is motion pictures or movies as it’s usually referred to. The term film is often used for this, but video no longer uses photographic film. However, that’s how it all got started.

Edison created the modern movie projector using George Eastman’s (Kodak) film, but they didn’t conceive of the idea of making moving pictures. That goes back to the mid -19th century where people created a series of pictures that could be flipped through to simulate motion. A guy by the name of Eadweard Muybridge developed the first animated image sequence in 1870, but this was crude by today’s standards.

This illusion of animation concept ended up being used in the creation of movies. It seems that the brain imposes a persistence of vision effect to what our eyes see. This theory proposes that an afterimage persists for one twenty-fifth of a second in the retina of our eye. This theory makes movies possible. What happens in a movie projector is that the image is blanked out by means of shutter fast enough to not be perceived until the next frame is projected. This phenomenon takes place in the brain, not the eye.

These ideas are based on the phi phenomenon, which is the optical illusion of perceiving continuous motion between separate objects viewed rapidly in succession, in other words, the illusion of motion from changing static images.

The other phenomenon involved in video perception is beta movement, which is the apparent motion between different light sources that are periodically switched on.

Both of these are perceptual illusions that are responsible for the illusion of motion in videos.

Or not . . . there seems to be a lot of disagreement about how the brain sees motion in videos.

Actually, projectors double the shutter speed to help avoid the blurring when a film frame is advanced into position and then moved on, meaning that the shutter is running at least twice the frame rate. Some even ran at four times the rate.

At first, film was projected at 18 frames per second, but this resulted in flashing or flickering. Modern film is projected at 24 frames per second to avoid this annoying effect. This same rate was used in the first analog video cameras, but since the advent of digital, this frame rates have risen to 30 frames per second or even higher.

A higher frame rate avoids blurring caused by fast motion. The higher the frame rate the less blurring on sees when the video is shown at normal speed.

TV had this same flicker problem because in the old analog TV systems the image was laid down on the screen using interlacing--scanning the odd and then the even number of lines--so that the screen was scanned twice for each frame. Eventually, computer monitors abandoned interlacing and used a refresh rate greater than 60 Hz. Lower than that, the monitor suffered from a flicker effect. Most modern monitors used 85 Hz or higher to minimize flicker.

The new LCD monitors and TV’s don’t suffer from this flicker effect even at less than 60 Hz rates. This is because a LCD pixel is always generating light as long as it’s activated. The image processor determines if the pixel needs to be lit or not lit and this happens at very high speed.

No matter how you look at it, video is an illusion of motion created in the brain by projecting still pictures that change at a high rate to fool our vision into thinking they’re moving. What we see in real life is motion, but it’s probably a similar illusion because of how vision operates in the brain. The eyes see a series of still images that are sent back to the occipital region of the brain to be put together to form a movie of the real world. In other words, we’re seeing videos all of the time. Could I see a new Harry Potter movie, Mr. Brain?

Thanks for reading.