Opaque Projector vs. Overhead Projector: How Do They Work?

Opaque projectors and overhead projectors are two of the earliest forms of projector. While there have been many advances in technology since these two projectors were first made, they are both still in use today.

These projectors are convenient for presentations, lectures, and class lessons. They are simple and easy to use, which is why they are still popular in some settings today.

How Do Opaque Projectors Work?

Opaque projectors can display opaque or 3D images that you place below where the image is captured from. They use lenses, mirrors, or prisms to display an image.

A very bright light is used both on the source of the image and then to project that image onto a wall or a screen.

How Do Overhead Projectors Work?

Overhead projectors are shaped as a large box, with a long arm extended above it. The large box produces a bright light, and the long arm has a mirror that directs the light from the box onto a screen or a wall.

The image that it projects is from a transparent film placed on top of the light on the large box part of the projector. On this film you would write with a marker, and those words or images would be displayed onto the wall. Read more.

Similarities

As both opaque projectors and overhead projectors are early designs, they have many similar situations that they can be used in.

Both are commonly used in classrooms and meetings as a form of teaching or giving a presentation. They can easily project handwritten notes or sketches, and are good alternatives to blackboards and whiteboards.

They are simple to use, and do not require extra technology to give an input for the image, like a modern projector might use a computer or phone.

Neither of these projectors can be used to display a moving image, so they can’t be used for common entertainment purposes, or for displaying more advanced material or images.

Differences

These two projectors have different mechanisms, which makes the images that they display different.

Most notably, opaque projectors are able to display an image from an opaque surface, whereas overhead projectors are only able to project an image from a transparent surface.

This means that opaque projectors can be used in a lot more situations than overhead projectors. They are commonly used by artists to project images that they could then paint or trace onto paper or a canvas.

Opaque projectors can project book pages, photographs, and even objects.

Overhead projectors are only able to project images from what is written on a transparent piece of film.

Pros of Opaque Projectors

Opaque projectors are very versatile. There are many opportunities for their use because they can project pretty much any image that can fit under where they capture the image from.

In a lecture, classroom, or meeting setting, you would be able to display notes, charts, images, or objects that you have already prepared ahead of time. This removes any need to be writing or creating something as you’re giving a presentation.

Even if you can have everything prepared, you are still left with the option of drawing or writing something up in real time to present. You could easily clarify a question, such as a teacher creating a sample problem and solution for a confused class.

Opaque projectors can also be used for artistic purposes, as they’re great for enlarging images for reproduction or tracing onto other canvases or paper.

They can also show images in color, and are good at showing motion as well.

Cons of Opaque Projectors

Even though there are a lot of different uses for an opaque projector, they don’t have the capabilities of other projectors.

You could not comfortably show a movie or a video through an opaque projector, even though it shows color and motion like other modern projectors.

Since they show a range of colors and textures, you would also occasionally need to refocus an opaque projector, or wait for it to refocus itself.

If you are writing notes, the color or tone of your hand or your sleeve might throw the contrast balance off, and it would need to rebalance once you’ve removed your hand.

If you are showing an object or image, it might need a second to refocus so it projects the image clearly.

Even though using an opaque projector to display images and notes is great for convenience, you do have to deal with some technology issues here and there, which you wouldn’t have if you were using a simple blackboard or whiteboard.

Pros of Overhead Projectors

Overhead projectors are great for teaching a class or presenting notes. They work in a very simple way, and you wouldn’t need to understand much about technology to be able to use an overhead projector properly.

When you are using an overhead projector, it’s helpful to be able to talk through what you are writing down with whoever is listening, whether you’re at a professional meeting or learning in a classroom.

Essentially, it’s a great way to take real time notes for an audience, regardless of what it is that you are writing down.

Cons of Overhead Projectors

Since overhead projectors work through a series of light and mirrors reflecting marks on translucent film, they are not able to show colorful images. They are only able to show whatever is drawn onto that film.

This makes their usefulness very limited. They cannot be used in as many different situations as an opaque projector, or a modern model of a projector.

They are also not able to show motion. Technically, you could see a marker writing letters on the translucent paper, but the view would be obstructed by a person’s hand until they were finished with writing.

Essentially, overhead projectors are only capable of projecting a very small amount of things, and the translucent sheet would need to be cleaned and changed often as you are presenting using that projector.