Getting a projector set up correctly is often more involved than putting a TV on the wall, which is ready to use.
Projectors must be aligned correctly, adjusted (not just focus and zoom), and dialed in to produce the most accurate and vibrant image possible.
So then the question arises what is keystone in a projector, and why should you use it when it is necessary?
Keystone correction in a projector can sometimes be a valuable tool to get your image alignment. A digital process engineered to perfectly align the projected image with the surface you are projecting on, keystone correction works best with images that are horizontally misaligned.
At the same time, there are some image quality trade-offs you’ll have to make if you use keystone correction.
We go more in-depth on that below.
What is Keystone in a Projector?
A projected image is keystoning when projected onto an angled surface (or projected at an angle to a flat surface), distorting the image from a square or rectangle into a trapezoid.
Maybe there’s only one place in a room where a projector can be set up, but unfortunately, it is at an angle to the screen or wall that it is projecting onto.
Or maybe the only surface that can be projected on is at a right angle of the surface.
The result, either way, is something that looks like an architectural keystone. Your image gets stretched and distorted, often significantly.
Keystone correction is designed to align that image with the surface it is projected onto – without you having to physically move the projector.
What is Manual and Digital Keystone Correction
Today’s projectors (usually) feature both manual and digital keystone correction capabilities.
Manual correction is usually in the form of a dial that allows you to change the angle of the lens projecting your image.
You turn the dial one way or another to swing the lens left or right (with a separate dial controlling vertical adjustments), manually adjusting until the image projected is closer to a square or rectangle.
Digital keystone correction (available on LCD and DLP projectors) uses artificial intelligence and algorithmic computing to change and scale your image even before it gets projected.
Using this feature will always result in a perfectly square image. Though image quality can vary depending on how much adjustment is needed.
Pros and Cons of Keystone Correction
First, let’s talk about the advantages of using keystone correction.
- The most apparent benefit of keystone correction is that the projected image ends up “square to the universe” instead of being a trapezium.
- It’s much less distracting to watch movies, shows, sports, or presentations on a screen format we are used to rather than at a noticeable angle and misalignment.
- On top of that, keystone correction allows you to leave your projector in place and correct the picture angle instead of moving the projector repeatedly.
- It helps you to avoid readjusting for lighting, focus, and other settings each time the projector is repositioned.
- Due to less space in dorm rooms, the keystone feature is used as they are not allowed to mount the projector on the ceiling.
Of course, keystoning introduces a couple of issues as well.
- If very little keystoning is necessary, the image quality reduction may be minor. If the keystone feature is used too much, then be prepared to see picture quality decrease.
- On top of that, keystoning will also introduce digital artifacts, image distortion, and “pixelated pictures.”
Is Keystone Correction Worth It?
So people always want to know “what is a keystone in a projector,”. Also is it worth it when mounting the projector whether on a ceiling or a flat surface?
Now, this option is only recommended as a last resort to fix the image when you did everything to fix it.
Keystone correction can be helpful in specific scenarios, but it’s always recommended to deal with image alignment issues in other ways before using this feature.
Image quality will drop off while doing keystoning significantly, and you need to be extra cautious when using this feature.
Do all projectors suffer from keystone image issues?
All projectors can suffer from keystone image misalignment if they haven’t been set up correctly.
Aligning your projector to the wall, you are projecting on is critical if you don’t know what you are doing.
Should I manually adjust my picture image or use my projector’s automated keystone tools?
Manual keystone adjustment works best when you are adjusting an image horizontally.
But if you have to adjust an image vertically or horizontally, the digital keystone feature should be used if your latest projection system has this feature.
What’s the best way to fix keystoning?
The best way to fix keystone problems with your projector is to physically move the unit in better alignment with the surface you are looking to project.
Remember doing the keystoning even a bit will result in at least some image degradation.
Keystoning your projector (digitally or manually) may be necessary for certain circumstances.
It’s a great feature when you want to align the image correctly on the wall or the screen, which is available in almost all the latest projection systems.
That being said, the better aligned and parallel you can get your projector to your projected surface, the perfect picture you will see on the screen or wall.
Keystoning, when done incorrectly, even just a little bit, will alter the images you are projecting, and there will be a drop in quality that will be noticeable immediately.
Avoid keystoning whenever possible.