Can projectors work at an angle?

So you want to purchase a projector for that awesome home cinema or conference room setup, however, you know that you won’t be able to perfectly align the projector in such a way that the image may be skewed.

So you ask yourself, can projectors work at an angle, and the answer to this question is yes they can. To ensure that the image is straight when the projector is at an angle to the screen, you can use keystone correction and/or lens shift to achieve this.

This article is the ultimate guide to getting your project to work at an angle.

What is keystone correction?

Keystone correction, otherwise known as “keystoning” is the ability to adjust the projected image so that you can align it correctly in an even/straight rectangular format.

There are two types of keystone correction The first is vertical keystone correction. This is what is used when the projected image is either smaller or larger at the top or bottom of the image.

This is often caused when the project is either tilting upwards to the projector screen from below or when the projector is tilting downwards to the screen from above. If your projector isn’t raised or lowered directly in front of the screen the image will be larger at either the top or bottom of the screen.

The second type of keystone correction is horizontal keystone correction. This is what is used if your projector is slightly larger to the left or right of the projector screen.

This is caused by a projector being positioned either slightly to the left or right of the centre of the projector screen. If your projector isn’t centred, the image will display either larger to the right or left of the screen.

Keystone correction or keystoning will adjust the image itself so that it counteracts the angle of the projector screen to the projector. This change in the image will then straighten the overall image displayed to the viewer.

Be aware that although a lot of projectors offer a vertical keystone correction, not all projectors offer horizontal keystone correction.

What are the drawbacks of keystone correction?

The main drawbacks to keystone correction is a degradation to the image resolution and sharpness of the picture. This means that the picture may look less detailed and rich and may have blurred areas, usually around the edge of the projector screen.

This isn’t all bad though as the section above details the main positives of using either vertical or horizontal keystone correction.

The reason that keystoning can degrade a projector image is that it is a digital manipulation of the projected image rather than a physical adjustment of the lenses.

In order to shrink the image at either the top, bottom, left or right of the image so that it fits within the projector screen frame, the projector will reduce the number of pixels in the image itself.

This can cause what was a very detailed picture to become quite pixelated or even blurry. Also, lines that would have once been straight are then projected as jagged lines.

That said, if your projector is capable of projecting high-resolution images such as 4K or 1080p, then the final image projected may still be of high quality that no one will really notice anyway.

For instance, a 4K image may be reduced to something more like 1080p after the horizontal or vertical keystone correction has been performed. Just like a 1080p image might be reduced to 720p.

As you can see, although keystone correction might reduce the image quality, it might not reduce so much so that it outweighs the point of performing it.

What is lens shift?

Lens shift if the ability to either manually or mechanically adjust the physical lens itself in order to distort the image so that it appears straight within the projector screen. Lens shift does not distort the image before it is projected, as it does in keystone correction, but instead manipulates the optics to adjust the angle of the image.

Depending on the model of the projector, the lens can be shifted either upwards, downwards, left, right or even diagonally within the projector housing.

This is a perfect solution if your room doesn’t allow you to fix a projector in place so that it is perpendicular with the screen, such as with a coffee table in your living room.

What are the drawbacks of lens shift?

Although lens shift offers many more benefits than either vertical or horizontal keystone correction, there can be drawbacks to using lens shift to adjust the angle of your projected image.

The most notable drawback is that lens shift can decrease the focus of the image within certain areas of the projection itself. This may not always be the case and it will vary on a number of factors including the throw distance, angle to the screen, model of projector etc. There are many variables within this equation.

The main cause of the degradation in focus is that all lenses have an area on the glass that offers the most optimal image quality and focus. If the lens has been shifted within the housing, as the light is projected through the glass, it may travel through parts of the glass that have a lower lens quality.

Therefore lenses have sweet spots. If you have adjusted the lens via lens shift so much so that you aren’t hitting the focal sweet spot, then the resultant image may look fuzzy and blurry in certain areas.

There is no way of knowing if this is going to affect you without trying it first, so you might get lucky or you might not.

All in all, though, the potential drawbacks of lens shift are far lower than using keystone correction.

Can you tilt a projector?

Yes, projectors can be tilted. A tilt in the projector can be achieved in two ways.

  1. Manual tilting using either the projector feet or projector mount.
  2. Keystone correction.

We will explore the first of the three. Most projectors come with a set of feet that will unscrew from the base of the projector to tilt the projector upwards so that it can face the projector screen. The maximum angle of the tilting available will differ between each make and model of the projector as the length of the feet themselves will be different.

Projector feet are usually used when the projector is placed on top of a surface like a desk or stand.

Another manual way of tilting a projector is by using a ceiling projector mount. The mount is bracketed to the ceiling at one end and the projector is attached to the other.

Projector mounts usually allow the installer to adjust the projector so that it can tilt downwards towards the projector screen.

The options above are all manual or physical ways of adjusting the image. Next, we will discuss the digital way of tilting a projector.

This is known as keystone correction. Keystone correction doesn’t physically tilt the projector itself, however, it does tilt or distort the image projected. Keystone correction is necessary when the projector isn’t perpendicular to the projector screen itself.

There are two types of keystone correction The first is vertical keystone correction. This is what is used when the projected image is either smaller or larger at the top or bottom of the image.

This is often caused when the project is either tilting upwards to the projector screen from below or when the projector is tilting downwards to the screen from above. If your projector isn’t raised or lowered directly in front of the screen the image will be larger at either the top or bottom of the screen.

The second type of keystone correction is horizontal keystone correction. This is what is used if your projector is slightly larger to the left or right of the projector screen.

This is caused by a projector being positioned either slightly to the left or right of the centre of the projector screen. If your projector isn’t centred, the image will display either larger to the right or left of the screen.

Keystone correction or keystoning will adjust the image itself so that it counteracts the angle of the projector screen to the projector. This change in the image will then straighten the overall image displayed to the viewer.

Can I put a projector in a corner?

Yes, a projector can be placed in the corner of a room however, your projector will need to include horizontal keystone correction and possible even lens shift capabilities.

Presuming that the room in question has a floor plan that is roughly square or rectangular the projector is probably going to be projecting against a fairly steep angle. This will require a lot of keystoning and lens shift to make it appear square from the point of view of the viewer.
As mentioned earlier in the article, using a significant amount of keystone correction will likely result in a reduction of the overall image resolution.

If you must locate your projector in the corner of a room for reasons such as that is the only location of a power outlet, it would be recommended to swivel the projector around as much as possible so that the projector is facing the projector screen with as straight-on as possible so to reduce the angle and therefore the amount of horizontal keystone correction and lens shift.

Do projectors need to be straight?

Projectors usually come with a number of inbuilt features that remove the need for the projector to be centrally aligned or facing straight on with the projector screen.

The three options are horizontal keystone correction, vertical keystone correction and lens shift. All three of these options will mean that the projector will not have to be centrally aligned with the screen.

That said, they can only offer limited amounts of correction due to either digital or physical limitations. Therefore, although your projector doesn’t need to be completely straight-on with the screen, in order to ensure that the image will perfectly fit within the screen, it would be advisable to mount or place the projector as central as possible.

How much off centre can a projector screen be?

The amount that a projector can be off centre will depend on the make and model of the projector. Take a note of what the manufacturer states the maximum lens shift is of the projector.

This is usually written in the following format (although the values can change):

Horizontal +/-50% & Vertical +/-100%

Using the example above, you will be able to shift the image 50% of the total width of the projected image using the horizontal lens shift. The projector is also capable of lowering or raising the image by 100% of the length of the current image too.

That allows quite a large margin of error when it comes to placing the projector and therefore the projector above would not need to be anywhere near its centerline to be able to be viewed squarely within the projector screen.

How do you adjust the angle of a projector?

The angle of a projector can be adjusted in two ways.

  1. Manual tilting using either the projector feet or projector mount.
  2. Keystone correction.

We will explore the first of the three. Most projectors come with a set of feet that will unscrew from the base of the projector to tilt the projector upwards so that it can face the projector screen. The maximum adjustment of the angle will differ between each make and model of the projector as the length of the feet themselves will be different.

Projector feet are usually used when the projector is placed on top of a surface like a desk or stand and aren’t centred perpendicular to the centre of the projector screen.

Another manual way of adjusting the angle of a projector is by using a ceiling projector mount. The mount is bracketed to the ceiling at one end and the projector is attached to the other.

Projector mounts usually allow the installer to adjust the projector so that it can tilt downwards towards the projector screen.

The options above are all manual or physical ways of adjusting the angle of the image. Next, we will discuss the digital way of adjusting the angle of a projector.

This is known as keystone correction. Keystone correction doesn’t physically tilt the projector itself, however, it does tilt or distort the image projected. Keystone correction is necessary when the projector isn’t perpendicular to the projector screen itself.

There are two types of keystone correction The first is vertical keystone correction. This is what is used when the projected image is either smaller or larger at the top or bottom of the image.

This is often caused when the project is either tilting upwards to the projector screen from below or when the projector is tilting downwards to the screen from above. If your projector isn’t raised or lowered directly in front of the screen the image will be larger at either the top or bottom of the screen.

The second type of keystone correction is horizontal keystone correction. This is what is used if your projector is slightly larger to the left or right of the projector screen.

This is caused by a projector being positioned either slightly to the left or right of the centre of the projector screen. If your projector isn’t centred, the image will display either larger to the right or left of the screen.

Keystone correction or keystoning will adjust the image itself so that it counteracts the angle of the projector screen to the projector. This change in the image will then straighten the overall image displayed to the viewer.