How Does a Slide Projector Work? - Digital Converters

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How Does a Slide Projector Work?

Author: Aaron Cottam
How Does a Slide Projector Work?

The mechanical clicking of a slide projector is something familiar to even the most sheltered iPhone photographers. Of course, not many of us have frequent interactions with a slide projector, but the shh-kunk sound remains unmistakable. While the projector was a great source of entertainment, the fundamental mechanics of it remain a mystery. 

What Are Slides?

The innovation of slide photography begins with how it prints the picture onto the film. Unlike negative film, which inverts the picture’s colours when printing onto the film, the see-through film used for slide production keeps the colours the same. 

The film for slides was a much cheaper option for amateur photographers because they did not have to fork out for their film prints to be processed. Instead, the photographer had to mount their film into a glass frame. The slide could then be inserted into a projector to view the photo.

How Are Slides Viewed?

The main downside to slide photography is viewing the photo. You can hold the film up to the light to see what has been photographed. But, the photo’s size is much too small to see the photo’s beauty – or show it to larger groups. So, many observed the image through a projector. 

Once you insert a slide into a projector, a light shines through the film and into a lens. The lens works similarly to how our eyes do: it corrects the photograph by flipping and focusing the image for you. The photo is also enlarged by the lens and then projected onto a surface of your choice.

Funnily enough, the invention of projectors came before photography.

The Magic Lantern

You may have stumbled upon this article while reading about slide photography. In that case, you may already be aware of the Magic Lantern slide projector. But for those who are not experts in projection technology, I will give you a quick recap:

Christiaan Huygens, a Dutch scientist, developed the magic lantern in the 15th Century. Huygens was a little camera shy and regretted inventing the technology as soon as he realised its popularity. He even planned to sabotage his invention upon finding out his father had intended to present the lantern to the King of France, Louis XIV. Huygens reportedly urged his brother to make sure no one used the Magic Lantern.

Unfortunately for him, schools and theatrical productions used the magic lantern for centuries to come. It also remains a product of interest today – although mainly in the minds of vintage enthusiasts and collectors.

The Magic Lantern’s main mechanics remains the same in projectors. The components needed are the same: a light source, a lens, and the see-through slide image. The only difference between the original lantern and the projectors today is the content of the slide itself because the lantern used paintings and drawings instead of photographs. 

An example of a painted slide by Joseph Boggs Beale (1841-1926)

An example of a painted slide by Joseph Boggs Beale (1841-1926)

Two hundred years later, photography entered the world, and the magic lantern’s mechanics came back into the limelight.

Slides in the Present Day

Of course, most people prefer digital photography nowadays. However,  nothing beats the sensory feeling of loading a slide into a clunky, vintage projector, clicking the switch and hopping in and out of worlds frozen in time. If you, or your family, have boxes of tiny, old pictures stored in the attic, these will likely be slides!

Unfortunately, the labs which previously churned out thousands of processed slides are now slowly disappearing. To save your slide photos from disappearing, get them digitised today with the UK’s #1 photo digitisation service! Digital Converters will ensure the preservation of your photographs for years to come.