Summary
- Keystone correction helps adjust the shape of the projected image, either manually or automatically.
- Be cautious of using excessive keystone correction to avoid a reduction in image fidelity.
- Consider projectors with lens shift capabilities for superior image quality without digital adjustments.
If you’re considering replacing a smart TV with a smart home entertainment projector, or even if you’re just looking to supplement a TV with one, there are plenty of considerations to make before purchasing. While smart TVs and projectors share some similarities in terms of picture quality, audio capabilities, HDMI ports, and smart systems, there are also some unique qualities to projectors worth understanding.
The main difference between a smart TV and a projector is how the image is produced. Instead of a backlight or individually-lit pixels of a smart TV, a projector casts an image onto the surface, and how that image appears involves an important concept: keystone correction.
Here’s everything you should know about this feature that helps make the screen enjoyable.
What is keystone correction?
Important alignment adjustment
The ideal projector setup has the lens pointed directly at the screen, perfectly level and balanced. When it’s at the right height, projecting in a straight line to the vertical surface, the project produces a rectangle. However, often it’s difficult to achieve this setup. Your projector may sit on a table and point upward, or you may have one mounted to the ceiling, where it will end up tilted down. The result of a projector that isn’t directly pointed at the screen tends to be a trapezoid; the image may be wider on the bottom or the top, or even either side. And that’s not ideal for watching entertainment.
Keystone correction is the process by which you adjust the image so that it becomes a rectangle. It’s an important component in projectors. However, it’s important to note that there are different types of corrections, and that there may be consequences if you’re making too many drastic changes.
Keystone correction is important for a couple of reasons. Firstly, watching a film that has uneven edges is unnerving and disorienting. Movies and shows aren’t filmed as trapezoids and aren’t intended to be viewed that way. More importantly, perhaps, is that watching at such an angle is going to distort the image, resulting in a distracting viewing experience that lacks fidelity to the source.
Types of keystone correction
Manual and automatic options
Your projector may have one or more types of keystone correction to help you adjust the final image. A common correction is done manually, with the projector allowing you to adjust the image either vertically, horizontally, or both. Vertical correction tends to be more commonly found than horizontal because users are more likely to tilt the projector up or down as opposed to side-to-side.
Manual adjustment involves opening up a setting that will put up arrows on the screen, allowing you to adjust sides or corners as needed. This process can be slow and tedious depending on the initial setup. Some projects may only offer two points of adjustment, but more advanced models may allow for four or eight points to be adjusted for more control and precision.
Keep in mind where you are planning to use your projector; the type of keystone correction offered may limit its usage.
Alternatively, some more advanced projectors may feature automatic keystone correction. In this case, the projector detects the angle at which the image is being thrown, and then makes quick, internal adjustments so that the result is a rectangle. This option is more convenient and especially useful for those who are often moving the projector.
There are also some advanced keystone options available on high-end models. Some projectors may detect the edge of a screen to fit the surface, while others may take note of aberrations on the surface, such as a light switch or nail on the wall. Auto-keystone correction may also be combined with an automatic focus feature.
Keystone correction consequences
Be mindful not to sacrifice quality
As you adjust the image, the image may lose quality as a result. As the keystone correction is a digital adjustment, the image may see a reduction in sharpness or resolution. The extent of any loss in fidelity will depend on how drastic the adjustment is, the quality of the media you’re watching, and the quality of the projector.
Typically, a projector will list how much it can correct the shape of an image before it starts to lose image fidelity. This is expressed in degrees, with a higher margin allowing for more adjustment without sacrificing quality. For those enjoying casual viewing, using keystone correction shouldn’t result in too many problems. However, for those enjoying premium home entertainment, you’ll want to avoid using the keystone as much as possible in most cases.
Keystone correction and lens shift
A superior alternative on premium projectors
If you’re worried about keystone correction resulting in a lower-quality image, then consider projectors that feature a quality lens shift. Instead of digitally adjusting the image, a lens shift will physically move the lens itself, meaning the image can retain more fidelity. It may move vertically or horizontally, while the projector stays still. Lens shift capabilities are expressed by the percentage of a screen’s height and/or width, depending on if the shift is vertical or horizontal (or both).
Typically, you’re only going to find a lens shift feature on mid-range or high-end projectors. This will be offered on premium models that are designed for home theater usage in which the projector is kept in a static position. While these projectors will also offer keystone correction, it may not be necessary to use them. Although, it might be helpful to fine-tune any final adjustments to your entertainment setup.
