Have you ever wondered how specific lenses make an object appear bigger than they are?
Take a magnifying glass, for example. If you peek through a magnifying glass, it makes any subject look bigger.
For the kids, it works like magic. But for us? It’s simply science!
Like a magnifying glass, projectors have convex lenses that enlarge whatever subject is placed before it. Convex lenses come with a bent-outward surface and are thick down the center. This shape, along with a light source, allows them to magnify any subject or moving picture.
The convex lens is the bread and butter of projection optics. Most projectors in the market, new or old, will likely have convex lenses.
But as projectors become more advanced, so do the lenses that come with them.
Let’s dig deeper into the types of lenses used for projectors.
What are lenses?
Before we get to the bottom of things, let’s first understand what lenses are and how they work at the primary level.
A lens is a device that bends light in a certain way. Lenses can either be simple or compound.
A simple lens uses one lens (ex: magnifying glass, Magic Lantern lens). On the other hand, a compound lens utilizes multiple lenses combined (ex: modern camera and projector lenses).
The first projector invented, the Magic Lantern, contained only one simple lens: the convex lens. At the time, this lens was a breakthrough for projection optics—you could even say it was the earliest form of screen sharing.
But having only one simple convex lens for a projector meant you’d have to deal with light refraction flaws like spherical and chromatic aberrations. In short, having only a single lens in a projector gives you poor image quality—edges are blurred, and colors sometimes bleed out.
And so, not long after, Magic Lanterns with compound lenses came into the mix. Combining two or more lenses helped correct the refraction flaws present in the single-lens Magic Lanterns.
As a result, the picture quality became crisper, more precise, and sharper.
This innovation eventually paved the way for more advanced projector technology, and we’ve never looked back since.
Prime lenses have a fixed focal length. Unless you physically move the whole projector unit forward or backward, you cannot zoom the projected image in or out.
Short, ultra-short, and long throw projectors typically have prime lenses. Because of their fixed focal lengths, these projectors function differently. Depending on how far or near the projected image is ‘thrown’ or flashed onto the screen.
This distance between the projector and screen is called ‘throw.’
Short-throw projectors work best when placed three to five feet away from the screen, hence the name ‘short throw.’ They thrive best in tight spaces such as a gaming or entertainment room.
Short-throw projectors can function as such because their lenses have a short focal length of about 24-35mm. The shorter the lens’s focal length, the greater the image width flashed. Hence, the closer you can bring your projector to the screen.
Some short-throws are also engineered with a chip that can calibrate a projected image size proportionate to its throw distance.
Ultra-short throw lenses
Most ultra-short-throw projectors are marketed as an alternative to smart TVs. You can place them directly below the screen, like where you usually put your Apple TV or Roku.
Ultra-short throw projectors use folded optics—a system that dramatically increases the zooming power of its lenses.
Because ultra-short-throw projectors are powerful, having the ability to cast large images in extremely short distances (3-20 inches) can be very expensive.
The most common type of projector lens is long-throws. These projectors are usually found in church halls or big auditoriums.
Long-throw projectors need at least a throw distance of 6 feet and are designed to work best when it’s further away from the screen.
While long-throw projectors shine in grandiose spaces, that doesn’t mean you should cross them off your list if you’re simply buying a projector for your home theater.
Long-throw projectors will work just fine in your home unless you have a tight space.
Micro Lens Array (MLA)
Micro lenses are known for delivering high image quality projections.
Inside an MLA projector, tiny lenses less than the size of a staple wire all redirect light that would have otherwise leaked. As a result, you get a brighter image quality than your standard projector.
An added benefit to this design? Thanks to the lenses, your projector unit packs in less heat because of the efficiency in collecting light.
A lens shift projector enables you to move your lens via a joystick or menu buttons. This feature combats the dreaded ‘trapezoidal shape’ you get when your projected image is misaligned with your screen. This is known as keystoning.
There are three types of lens shift projectors:
- Horizontal lens shift – the lens move left or right
- Vertical lens shift – the lens move up or down
- Variable lens shift – the lens can move diagonally
Keystone correction is a feature most projectors have. It serves a similar function as the lens shift but has one great downside.
A keystone correction feature is a digital feature that impacts the resolution of your projected image.
So while keystone correction and lens shift can prevent misaligned edges, lens shift projectors are far superior because they don’t mess with the quality of your projected media.
Choosing the right lens
Projectors, unlike televisions, are comparatively niche. You have to be more mindful of certain variables before purchasing the right projector for you.
Starting with the different types of lenses—short throws, long throws, lens shift, etc., makes it easier for you which projector to consider.
Lenses play a vital role in the performance of a projector. They define the capabilities and limitations of the projectors they are housed in most of the time.
Choosing the right projector means having to choose the right lens as well.
You must consider the space you plan to put your unit in and the primary function it will serve.
Will you plan to use it for games? For movies? For presentations?
These are the factors you need to consider before choosing your type of projector lens.
Vance is a dad, former software engineer, and tech lover. Knowing how a computer works becomes handy when he builds Pointer Clicker. His quest is to make tech more accessible for non-techie users. When not working with his team, you can find him caring for his son and gaming.