Put simply, aspect ratio refers to the shape of the image being projected. Almost all projections today are in the shape of a rectangle, but exactly how wide or narrow is determined by the aspect ratio.
Choosing the aspect ratio of your screen can be very confusing because the screen, projector and video source can all be different and both the projector and video source can usually be zoomed or scaled to change aspect ratios. An image with an aspect ratio of 4:3, for example, means the width of the image is 4/3 or 1.33 times the height of the image. An image with an aspect ratio of 16:9 means the image is 16/9 or 1.78 times the height. In our opinion, though, the most important thing to consider is the native aspect ratio of your projector followed by the aspect ratio of the images you will most commonly be projecting.
- 4:3– While there are, technically, many different aspect ratios used around the world for different video formats; the most common are 4:3, 16:9, and 2.39:1. The most common used to be 4:3 (think of old CRT television sets). You will also still find projectors, usually marketed for office applications have a 4:3 aspect ratios. Standard definition television, "standard format" DVDs and most other devices connect with analog composite cables (think yellow/red/white RCA cables) and will output video in a 4:3 format. If you use any of those consider a 4:3 aspect ratio screen.
- 16:9– Conversely, most new home theater projectors have a native resolution with a 16:9 aspect ratio. HDTV, Blu-ray and most other devices, connecting via HDMI or other digital video cable, output video in a 16:9 format. An appropriate choice for a screen in those situations would have a 16:9 aspect ratio.
- 2.39:1– Even with a 16:9 projector and a 16:9 video output the image may still have black bars and won't use the full height of the screen. This is often referred to as letterboxing and often occurs on movie releases where the producers of the media choose to keep the original cinematic aspect ratio and fill the rest of the image with black. Because of this, some people choose to build screens at wider aspect ratios (2.39:1 being the most common) so they can fill the screen with the wider image. Often this just means using the projector to zoom out so the black bars are off the screen (some projectors have a built-in memory to switch between zoom levels).
The optimum screen size for a given seating area is a largely subjective choice, but we like to follow recommendations made by a few organizations like THX and the Society of Motion Picture and Television Engineers. While a great amount of material on the subject can be easily found online (consider starting at Wiki's-Optimum HDTV viewing distance), the many opinions can be summarized fairly simply.
If you take the height of your screen and multiply it by two, that's about as close as you want to sit to a screen before it becomes a little uncomfortable. Similarly, any seats greater than about four screen heights away will start to have their experience diminish, and after five or six screen heights away the screen is really too far away. So, a great middle ground is to find the distance from the screen to your optimum seat, divide by three, and that's the best height for a screen. The width or diagonal of the screen can be then determined from your chosen aspect ratio.
- For one example, imagine you're building a screen for your new home theater where you will almost always sit about 165 inches from the screen. 165 divided by 3 is 55, and so your screen should be about 55" tall in that situation. Assuming a 16:9 aspect ratio for a 1080p image, the width would then be 55*16/9=97.78". You can then use Pythagorean's Theorem to calculate the diagonal size of about 112".
- For another example, imagine you have one of our 9x16 Standing Kits and want to know how large of an audience you can serve with it. The viewable height on that screen measures 105", so ideally the audience should sit between 105*2=210" away and 105*4=420" away. It would not be unreasonable to extended seating back to 105*6=630". Converting to feet you would want your audience between 17.5' and 52.5' away with optimum seating being about 26' away. How densely you pack the seats into that area would, of course, be up to you.
We also offer a Projection Screen Material Comparison Chart which assists you in finding the best material for your needs, but it's good to have some understanding of screen color and gain.
Screen Color: High contrast gray surfaces generally mean, compared to white surfaces and when paired with a relatively bright projector, the image will have a greater contrast with deeper blacks. White surfaces work best when ambient light is controlled.
Screen Gain: Screen gain is a relative measure of reflectivity of the projector screen. The number represents a ratio between the measured brightness of a screen coated with a standard matte white material (usually magnesium carbonate or titanium dioxide) and the screen itself when measured perpendicular to the screen.
- For example, if a reference image is projected upon a standard matte white material and the brightness is measured, then the screen material in question would have to measure 110% of the same brightness, while using the exact same image and projector setup, to measure in with a gain of 1.1.
A material that is the same brightness as the reference material would be 1.0. A 1.0 gain screen diffuses light evenly in all directions so seating can be placed at wider viewing angles. Many gray screens reflect less than a standard white material and so it's normal to see gains in the range of 0.6 or so. Lower gain screens are good when you have higher amount of ambient light, but require brighter projectors.
Similarly, some materials provide a gain of 1.5 or higher and usually accomplish this by better focusing the reflection toward the audience. This can lead to a brighter image but usually comes with the tradeoff of having a narrower viewing angle and the risk of hotspots (seeing the direct, bright reflection of the projector bulb). Higher gain screens were more popular years ago when projectors had significant limitations in their brightness, but some high gain screens are still necessary for specific applications, such as 3D screens with passive/foil glasses.
Before your final Projection Screen Material selection ask yourself these questions:
- Will I be using my projector screen indoors or outdoors?
- Do I have a dark viewing environment or do I have ambient light concerns?
- What kind of frame will I be building? A permanent fixed-frame with screen material stretched onto the frame? A portable frame where the screen is tension-mounted/stretched but can be easily removed? Or do I plan to attach it directly onto the wall?
- Do I have other specialty requirements such as; Rear Projection, Acoustically Transparent or 3D Projection?