CHOOSING THE RIGHT PROJECTOR SCREEN: Screen Size and Aspect Ratio
Choosing the Appropriate Screen Size
While many users may want the biggest screen that fits on their wall, sometimes bigger may not be better. If your room is not large enough or the projector is not bright enough a smaller screen could be a better solution.
A big screen in a small room requires more resolution
The bigger the screen, the farther away a viewer needs to sit to watch comfortably. You’ll also want to consider the projection setup. How close will the viewer be to the image and what is the resolution of the projector and content? Resolution and screen size will determine the optimal viewing distance.
The main benefit of a 4K projector is that the viewer can sit closer to a huge screen without seeing the pixels. For example, a person with 20/20 vision who is sitting closer than 3.2x the height of a Full HD image will be able to see the pixels while they would have to sit closer than 1.5x picture height of a 4K image to see pixels.
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A big screen in a small room requires shorter throw ratio
Even if a massive screen fits, you may not be able to move the projector far enough back to fill the screen. Throw ratio is the ratio of the distance from the lens to the screen (throw) to the screen width. Lower throw ratios result in a shorter throw distance. So, the size of the largest screen that can be used in a room vary by projector. Once the projector is chosen and its mounting position determined, then minimum and maximum screen size can be calculated. Usually, there will be a screen size chart in the manual, or you can easily search for an online calculator to help figure it out.
A bigger screen requires a brighter projector
Depending on the size of the screen and lighting conditions in the room, the brightness needed to deliver a good-looking image can vary significantly. A 2,000-lumen projector is bright enough to watch movies on a 120” screen in a dark room. However, if there is ambient lighting, a 3,000-lumen projector may be required to deliver a vibrant image.
In a business or classroom environment, which are never completely dark, to view a presentation on a 120” screen, even more brightness might be required to make the content clear and easy to read. While a high gain screen can boost the on-screen brightness, excessive gain can negatively impact the picture quality. A moderate amount of gain with a brighter projector is usually the best solution for someone who wants a massive screen.
Choosing the Right Aspect Ratio
First, what’s the aspect ratio of the projector and do you want it to match the aspect ratio of the screen? If they aren’t the same, your image will either be too tall or too wide for the screen.
Combing through the options can be daunting but narrowing down your choices and making a few decisions beforehand will ensure you end up with the right screen.
Aspect Ratios Used in Business and Education Applications
Many projectors being manufactured nowadays have a 16:9 aspect ratio. They are a perfect fit for watching Full HD (1080p) movies and content. You would think that 16:9 would be the most common standard for business uses like notebooks and computer displays but you would be wrong. While 16:9 is used in business and education applications, there are two other commonly used aspect ratios.
4:3: This older aspect often called 1:33:1 was invented over 100 years ago. For decades, it was the official standard for all US films, broadcast television, as well as computer displays. Until the late 1990s, computer display utilized resolutions like XGA (1024x768) and SVGA (800x600) which had a 4:3 aspect ratio, when the video industry began moving towards wider aspect ratio. By 2005, the wider 16:10 had overtook 4:3 as the most sold aspect ratio for LCD monitors.
16:10: This aspect ratio is primarily used in businesses and education. Quite a few notebooks and monitors along with business/education focused projectors use this aspect ratio. When compare to the earlier 4:3 aspect ratio, wider 16:10 displays are considered to be better suited for productive uses such as word processing and computer-aided design.
While 16:10 is still a popular aspect ratio for laptops displays and monitor market, 16:9 has overtaken it as the most popular ratio for business/education applications as well. Currently less than 20 percent of new monitors and laptop displays are 16:10.
This is because display manufacturers tend to source their panels from the same providers. Since 16:9 are widely used in home entertainment display, due to economies of scale, they have a lower cost. While 16:9 displays are popular and less expensive they are considered less suitable for productivity-oriented tasks, such as editing documents or spreadsheets and using design or engineering applications. Many laptop manufacturers like Apple and Dell continue to ship laptops with 16:10 displays. Commonly used resolutions that have 16:10 aspect ratio include WXGA (1280x800) and WXUGA (1920x1200).
16:9: This is the common aspect ratio HDTV content and screens have, a 1.78:1 width to height ratio (usually referred to as 16:9). Most flat panel TVs, computer monitors, and projector now utilize this aspect ratio with content in resolution like UHD (3840 x 2160) and HD (1920 x 1080 or 1280 x 720).
Common Video Screen Aspect Ratios
There are dozens of aspect ratios used in video production. Let’s discuss the three most common aspect ratios utilized in home entertainment content:
4:3: Older movies and standard definition TV used an aspect ratio of 1.33:1 (often called 4:3) where the image is 1.33 times as wide as it is high. Since most modern content is shot in at least the wider HDTV, it is rare that a standard screen would be chosen for a home theater or home entertainment project.
16:9: This is the common aspect ratio HDTV content and screens have, a 1.78:1 width to height ratio (usually referred to as 16:9). Most flat panel TVs utilize this aspect ratio with content in 1920x1080 and 1280 x 720 is designed to completely fill a normally HDTV screen. 4K UHD which has a resolution of 3840x2160 also has an aspect ratio of 16:9.
Widescreen – sometimes called Cinemascope, typically comes in either 2.35:1 or 2.4:1 aspect ratios. This aspect ratio is popular in cinema, so the majority of blockbuster movies are shot in this format. These aspect ratios are noticeably wider than the 16:9 (1.78:1) aspect ratio used for HDTV broadcast. When viewing those widescreen movies, you don’t see those gray letterboxes at the top and bottom of the image. To pair today’s projectors with a Widescreen, you’ll typically need either an Anamorphic lens to stretch the image, or a projector sporting what’s called Lens Memory.
Choosing a projector with the right aspect ratio doesn’t have to be confusing. It can be easily accomplished while paying attention to a few factors. One of the best ways to choose an aspect ratio for a projector is to find out the aspect ratio of the source that will be using the projector or the content that will be primarily displayed on it. The ideal choice for most home theaters and regular users will be a 16:9 projector as DVD, blu-ray and set-top boxes output images in 16:9 format. If your playback device supports a different aspect ratio, choose a projector that matches the aspect ratio of the device.
Just because a projector has a specific aspect ratio doesn’t imply it won’t be able to project images having a different aspect ratio.
Display Widescreen Aspect Ratio Content
While many movies are produced in widescreen (2.35:1 or 2.4:1), most projectors native aspect ratios are narrower (1.78:1 or 1.9:1) There are two different techniques used to display widescreen video on a widescreen screen in a professional cinema and at home while avoids lettering boxing.
Zoom Method: The simplest, and least expensive, method for CIH is the so-called ‘zoom method”. With this approach the projector’s zoom lens is set to project an image that fills the full width of the screen when projecting a movie provided in the wide scope format (there are many movies offered in Blu-ray Discs in this format). In this case, the black bars present on the Blu-ray recording will now fall above and below the visible area of the projection screen and the widescreen scope images from the movie will just fill the screen’s height and width. Then when projecting a program with a normal HD aspect ratio of 1.78:1 the projector’s zoom is adjusted to reduce the image size to match the vertical size of the screen.
This will produce unused space on the right and left of the screen, essentially with the image appearing in what is called a “pillar box” with vertical black bars on both the right and left sides of the screen visible area. In order to use the zoom method for CIH the zoom, focus and (in many cases) lens shift will need to be adjusted to correctly size, focus and center the image. This is not a very practical approach for CIH when using projectors with only manual adjustments.
Anamorphic Lens Method: The second approach for home theater owner’s seeking the traditional approach used in commercial cinemas. There are three key ingredients for implementing this approach.
First the projector must be able to optically and mechanically accommodate an external anamorphic lens placed just front of the projector.
Second, video processing must be provided to vertically stretch the image (either built into the projector or provided with an external video processor).
Third, a compatible add-on external anamorphic lens must be mounted just in front of the projector. Such anamorphic lenses work best when the projector’s lens has a relatively long throw ratio (i.e., providing lower magnification). This latter point means that you would typically need to set the projector’s lens toward minimum zoom and mount the projector toward the maximum supported projector-to-screen throw distance. The advantage of this approach is you can use all of the pixels on the projector’s display panels rather than three fourth of them (for a typical 1.78 aspect ratio HD projector). This is done by electronically vertically stretching the image by 33% then optically (with the add-on anamorphic lens) horizontally stretching the image by an equal 33%. This approach with high quality anamorphic lenses will result in a somewhat brighter image, around 5% to 8% but has the potential of introducing distortions due to the additional optics involved.
The thing to keep in mind is that matching a projector with the right screen can actually make your picture look better and conversely picking the wrong screen can actually make the picture look worse. Rather than approaching these two critical elements separately you need to view these two elements as equal parts of the same projection system. Don’t worry, while there’s a lot to keep in mind when choosing a screen to pair with a projector, the benefit is years and years of use and enjoyment.
When choosing the right aspect ratio for a home entertainment system the type of content played most often should be the main determining factor.
The standard aspect ratio for HDTV, and the new Ultra HDTV, is 1.78:1 (16:9) so if most of the video shown on the projection system is broadcast based content, this probably is the best option. While there will be letterboxing when watching widescreen content, the entire screen will be used most of the time since broadcast is the user’s focus.
The motion picture industry uses a wide range of aspect ratios for their theatrical movie releases with most modern movies having aspect ratios between 1.85:1 and 2.39:1. Most major motion pictures are shot for commercial release is shot in widescreen. If the projection system is in a dedicated home theater and will be showing mostly movies, a widescreen may be the best option. Just be sure the user knows that any HDTV content will have visible bars on the left and right.
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