A good number of us who use projectors must have asked the question How does a movie projector work?

Whenever we want to see a movie, a good number of us would prefer to see movies in cinemas which offer high definition ones. In most cases, this is enhanced by the kind of digital projectors which are used. The projector is a remarkable achievement of power-driven design, which is responsible for the fabrication of one of the choicest visual illusions ever.

A movie projector can be said to be a device which is used for showing pictures and films by casting it on a screen. It is an optical alongside a mechanical machine.

Just like a slide projector, a movie projector has some vital optical parts:

Source Of Light

The first sources of light which was used in movie projection, was incandescent lighting, until the 19th century when carbon arc lamps became widely used in a good number of cinemas globally. Another prominent source of light which was introduced in the mid-19th century, was the Xenon arc lamp.

The Xenon arc became preferable to the carbon arc, based on the fact that, it lasted for a longer period of time, than the carbon arc, whose duration was a maximum of one hour.

From what I know about a good number of lamp houses, when used in a specialist cinematic setting, they generate much hear which burns the film, if it remains motionless for less than a split second. Due to this, it is essential that a great deal of care be exercised in examining a film, to ensure that it does not get impaired.

Reflector And Condenser Lens

The presence of a reflector and a condenser lens in a movie projector, cannot be undermined. A reflector retransmits light which would have been exhausted, to the condensing lens.

The function of a condensing lens, is to converge both the direct and reflected light, in the direction of the film gate.

A Dowser

This is one of the parts of a movie projector which I like talking about. The dowser which is also known as the douser. The structure of the dowser, is a metal blade, which slashes off the light before it reaches the film. The dowser could either be automatically or manually controlled.

Some movie projectors could have more than one dowser, this they use as an electrical switch, the third dowser could be used for automatically closing down, when the projector reduces its functioning pace.

Dowsers are also known to safeguard the film at the same point when the lamp is switched on, and the film is stationary, this would avail the film from dissolving due to the elongated exposure to the heat which is directly emanated from the lamp.

The dowser also ensures that the lens is prevented from having any blemish which could be as a result of the intense heat.

Frame Advance And Film Gate

Another part which I would like to talk about, is the film gate and frame advance. Once the roll of film is dispatched across the source of light and the projector lens, the result which would be shown on the screen, is an incessant hazy sequence of images which would be moving from one end to the other.

For you to get a clear picture, the film which is moving, needs to be paused for a while, during which the shutter would be in the continuous process of closing and opening. The film gate is the point where the film is paused before the shutter opens. This principle is common for both movie projector and filming machines as well.

The film gate is also responsible for the provision of little friction in order to prevent the film from either moving forward or backwards save for times when it is driven to move the film onto the subsequent image.

The frame’s registration can be controlled manually by the person in charge of the projection. The frame registration’s pins would ensure that the film does not advance when the shutter is still open.

The Shutter

If you always have the question “How does a movie projector work?”, then the shutter is one part whose function you should definitely know.

It is the combined work function of the gate and the shutter which produces the illusion of one complete frame to be substituted precisely on another complete frame. The gate ensures the film is held still, during the period when the shutter is open.

When you are viewing a movie, the brain is deceived into thinking that a non-stationary image is displayed on the screen. This happens because the cylindrical shutter prevents the produced light when the film is moved onto the subsequent frame. This is the transition which we do not see.

Aperture plate and imaging lens

A projection objective functions by utilizing various optical components to guide the film’s image, to the viewing screen. Projection lenses are different in the focal length and aperture, because of the various numbers of needs. Various lenses are meant for various aspect ratios.

Viewing screen

In a good number of situations, the viewing screen is usually a reflective surface which could be a white surface or an aluminized one. A projector screen which is switchable, can be interchanged between clear and opaque with a safe voltage at 36volts, which can be viewed from both sides.

If you look well in a commercial theatre, you would discover that the screen has small well-spaced holes, numbering millions, which aid the transmission of sounds from the speaker which are most times positioned behind it.


Projector TVs, are a blend of two related technologies, the television technology, and the projector technology. These technologies are responsible for the placement of pictures on the viewing screen.

So, when next someone asks “How does a projector work”, you would be able to offer a bit of explanation based on this piece, which has undoubtedly been an eye-opener. We cannot overstate the importance of movie projectors, as they are known to provide a fantastic viewing experience.

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