All About The Zoom & Throw Ratio of a Projector

According to film terminology, “throw” is the distance between the screen and the projector, whether it’s a home cinema video projector or a movie projector. It’s the distance of the image that’s “thrown” into the screen, hence the choice of words. Projection affects the size of the image, such that the further away the projector is the bigger the projection ends up being if it’s a long-throw kind of projector.

In regards to Zoom & Throw Ratio, it showcases how far or close your image can get. Zoom helps calibrate the size of the projection and throw ratio helps you know how far you should place the projector relative to the screen. A short-throw lens or a short-throw projector can correct throw distance of a home theater projector in case your home cinema or den is too small. Most projectors have a long throw lens though.

Light Travel and Distance

Light speed is the fastest thing in the known universe. However, light doesn’t always travel as far as you’d want it to travel. Stars many times bigger than the sun are able to travel to mind-boggling distances and showcase themselves at nighttime. However, light on earth has a more limited reach, particularly if they’re lights from electronics like projectors or battery-powered devices like flashlights. High beams on cars can reach far but not too far.

At least in terms of projectors in-home or outdoor cinemas, this is also the deal. The projector lens is calibrated in order to push the projection out at a certain distance. If you go too close the projection shrinks. If you go too far the projection blows up to the point of being too large to be contained on the screen. Furthermore, being too close or too far can result in image issues such as the projection being:

  • Faint
  • Blurry
  • Faded
  • Distorted
  • Unfocused
  • Washed out
  • Stretched out

When a projector is being used to play movies at an outdoor cinema or drive-in theater you want it to be positioned correctly as soon as possible. It’s the same when it comes to home cinema, maybe even more so because you’re working with even less room and tighter physical constraints compared to a commercial venue.

10 Zoom Throw Ratio 04

Learn More about Throw Ratio 

Throw ratio is a related measurement to throw that refers to the ratio of the distance from the lens to screen relative to the width of the screen. If your projector has a large throw ratio then that means you have a more tightly focused optical system. This is a good thing. You want that in a display device like your projector. This shouldn’t be confused with throw distance, which is simply the distance from the screen to the projector lens.

  • Why Do You Need to Know Throw Ratio? You need to know the value of the throw distance of your projector in order to figure out how far the device will sit in your home theater, den, living room, bedroom, or business conference room. You need to know the throw ratio because it helps you determine the quality of your image relative to the throw. The throw ratio (TR) is calculated by width (W) relative to the distance (D).


  • Read the Manual:  It’s a “Captain Obvious” kind of moment but you should definitely read the manual. It might give you as detailed an instruction booklet as this article or at the very least reveal to you what you need to know about throw ratio. The manufacturer of your projector will inform you through the specs list or even the manual what the device’s throw ratio is. You’ll typically see a number followed by a colon and another number, like 2:1 or 1.5:1. That’s D/W in ratio form.


  • Throw Ratio Explained: If your projector has a 2.0 throw ratio that typically means 2/1 or 2:1 in throw ratio terms. The 2 represents the distance of your projector lens from the screen in feet, which is also known as the throw distance. Meanwhile, the number after the colon is the width in feet, such as 1 foot of screen width. For every 2 feet of “throw distance” is 1 foot of screen size. If your projector is 12 feet away then you end up with a screen width of 6 feet.


  • Calculating The Throw Ratio Is Easy: Get the throw distance value and the image’s width. Put them together as D/W or distance/width or throw ratio divided by the width. For instance, the most common throw ratio of a projector is 2.0. This means that for each image foot width, the projector is two feet away. In other words, it’s D/W or 2/1 = 2 or 2.0. Therefore, if you have a 5-feet image with a 2.0 throw ratio, then the throw distance should be about 10 feet.

Calculating The Throw Ratio Is Easy

  • Calculating The Width and Distance Are Easy Too: In turn, if you have 3.0 TR and an 8-foot width, then you need a distance of 24 feet. It’s simple math wherein W * TR = D or width times throw ratio equals distance. If you have a screen that’s 10 feet large and you have a projector with a throw ratio of 2.0 then in order to get the right size of projection, you need to have a throw distance of 20 feet. That’s 10*2.0 = 20 feet or width*throw ratio = throw distance or W*TR = D.


  • The Actual Formulas: Throw ratio is TR. Width is W. Throw distance is D. The formula for throw ratio is D/W = TR. Width is D/TR = W. Distance is W x TR = D. Now you can figure out how big your projector screen is supposed to be relative to the throw ratio of your projector and how far away you can place it. Or alternatively, based on measurements or allowable room in your home theater, you can pick a projector with the right throw ratio.

Learn More about Zoom Ratio

If your projector’s throw ratio is far, then the farther away your projector is the more blown up the image gets, so you need a bigger screen. If your projector’s throw ratio is near, then you can get away with shorter distances equals big enough screens. With that in mind, how about the zoom ratio? What is its relation with your projector’s throw ratio?


  • What Is Zoom? Your camcorder, camera, or binoculars all have the ability to zoom in or out on an object you’re trying to see and/or photograph. Zoom allows you to make an object bigger without moving. It’s the same deal with photo editor programs. However, you should be aware of the two types of zoom. There’s a lens zoom and a digital zoom. Digital zoom is terrible because it blows up a small portion of an image, leading to pixilation. A lens zoom at least allows you to maintain the integrity of the resolution.


  • What Is a Zoom Ratio? The projector lens of your projector allows you to decrease or increase the size of the projected image without moving the projector in case you have no choice but to place your projector at the absolute back of your room with no more space left beyond that. The typical zoom ratio is at 1.2. In other words, you can vary the image size is 20 percent smaller or bigger. The range of the zoom ratio can go as low as 0.4 and as high as 2.1.


  • What Are The Benefits of Zoom Ratio? There are several reasons why you should be aware of the zoom ratio. For one thing, if you have a mobile or pico projector, it’s advantageous to have a zoom lens to allow you to set up your device in rooms where you have no control of the screen size or projector placement. For another thing, if you’re dealing with a fixed installation projector then the zoom lens makes you more flexible when it comes to projector installation, such that if the projection-to-screen size appears off you just zoom in and out to correct the image size relative to the screen.


  • Maintaining the Integrity of the Projection: Those who have digital cameras and digital zoom know that it’s much better to use a lens to zoom than to zoom at the pixels of the projection. Digital zoom might be perfectly fine if you’re only reducing or enlarging a picture for a little bit, especially if you have a high-resolution image. However, your image becomes weirdly pixilated with jagged lines a la keystone correction if you overdo it. This is why a zoom lens is used to enlarge a picture optically rather than digitally. This maintains the integrity of your image quality.


  • Throw Ratio versus Zoom Ratio: Zoom ratio exists in order to deal with throw ratio miscalculations or issues with the screen size and throw distance. The zoom ratio of a given projector allows you to change projection size to match the screen size without moving your projector, especially if you have no choice but to follow placement on a given throw distance. This is especially true for mobile or pocket projectors used in conferences and presentations as well as fixed installations wherein you can’t move your projector any closer or farther than the installation allows.


  • Shopping for Projectors Based on Variable Zoom Range: The best projectors have a variable zoom ratio that can either zoom in or zoom out. It should be able to go lower than 0.4 and higher than 2.1 depending on how much money you’re willing to invest in a zoom lens. The higher your purchasing power the better your chances of getting quality lenses.  Alternatively, you can buy optional lenses for a projector that supports them separately to allow you to save the money needed to get them.


  • Works Like a Professional Camera or Rifle Zoom Lens: Much like the zoom lens of a professional camera or a rifle, projectors that use optional lenses can allow you to have different zoom ratios to suit your needs. You have to be prepared to pay for all of them though. With zoom lens and long-throw projectors, you can place your projector all the way to the back of the room. Meanwhile, short-throw projectors have the ability to create bigger projections at shorter throw distances.

Learn More about Throw Ratio

What Is The Difference Between Short and Long Throw Projectors? 

When buying a new projector, knowing the throw distance is important because the device can only be moved so far in order to produce a perfectly calibrated image at the correct distance. What’s more, zoom correction lens can cost quite the fortune. If you want to save money on zoom lenses while not having to worry about calculating throw distances, you should consider getting a short-throw or short throw projector instead as opposed to a long-throw or long-throw one. 

With that in mind, what’s the difference between the two anyway? 

  • Long-Throw Projector: A long-throw projector is a standard projector with a standard throw distance of 10 feet or so and a standard throw ratio of 2:1. These are your home cinema projectors that you place at the back of your room or your standard movie projector that’s also placed at the back of the theater. You need to calculate throw ratio relative to the distance or screen size because otherwise, you’ll end up with an unfocused projection.

These are also the projectors that you can effectively mount in a fixed position in your projector room then aim at the screen. In case you aimed wrong and it has a keystoning or off-center projection, you can correct it with keystone correction and lens shift respectively. However, if the projection is too large or too soft given an unalterable distance, you can depend on the zoom lens of your projector and its zoom ratio to fix things without worrying about pixilation.


  • Short-Throw Projector: Obviously, a short-throw projector has a shorter throw distance than a long-throw projector. A short-throw projector has a short throw distance wherein it can produce a decently large projection. The image is able to fit, for example, a 5-foot screen in width at a foot or less than a foot. Therefore, your throw ratio for a short-throw projector is at 5:1 or even 5:0.5, wherein a 5-foot screen is filled at a foot away or less than a foot. There are also ultra-short-throw projectors that can produce 100 feet screens at 15 feet away or has a 10:1.5 ratio.

Many short-throw projectors are of the pico or pocket projector variety since it’s easy to move the smartphone-sized projector around on a table to adjust the screen size. Also, you can tell if a projector is a long-throw or short-throw projector by the initials at the end of its serial number. Those ending with LT refer to long-throw projectors and those that end with ST refer to short-throw projectors as a rule of thumb. Sometimes, manufacturers don’t follow this unwritten rule.


  • Pros and Cons of Either Projector: A short throw projector is ideal in a classroom setup because it gives the teacher more mobility and flexibility. If you’re not planning on mounting your projector unto the ceiling then you can adapt well-enough with a short-throw device that allows you to move the projector around without creating a seating isle or moving the seating area of your students.

Ditto when it comes to business projectionists who wish to present impromptu slideshows and presentations at the conference or meeting room. Having a short-throw projector instead of a long one allows them more adaptability in short notice with minimal preparation. A short-throw projector is the smartphone or tablet equivalent of the standard projector.

Ironically, the most modern shot throws also work superbly with tablet or smartphone connections. All that convenience comes with a price, though. A long-throw projector is cheaper across the board compared to a short-throw one if you’re willing to deal with its many inconveniences. However, when used in a home theater setting, most of those issues of adaptability aren’t relevant anymore. You want a mounted or fixed projector in your home entertainment center anyway!

In Summary  

The throw ratio is a simple formula that allows you to compute image width or throw distance in a jiffy. You sometimes won’t be working with the same screen size depending on what you’re watching but there’s an applicable throw ratio formula you can use to consistently shift from distance to distance or screen size to screen size. Your manual should reveal to you the throw ratio and with it, you can figure out the size of the screen you need for a given throw distance every time.

As for the zoom ratio, it’s the throw ratio version of keystone correction. You can correct a screen that appears too big or too small for the screen you bought or a throw distance that you can’t adjust due to the size of the room or placement of the projector by fiddling with the zoom based on zoom ratio. If you have a zoom ratio of 0.4 to 2.1, which means you can reduce or blow up the picture by those percentages using a zoom lens to maintain resolution integrity.

Image Credit:

James Core

I love my projector system and I am here to help you find the right projector for your needs.

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