Frequently Asked Questions (FAQ) About Projectors

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(Last Updated On: June 11, 2019)

At this point you may be wondering, “Great. But I cannot answer any of these questions.” Or, “I plan to take the projector on the road and could be using it almost anywhere.” Often, with the little forethought, the “I do not know” can be whittled down to the educated guess. If that is not the case, you are not completely out of luck. In addressing every topic, we will suggest your best bet when confronted with the unknowns.

What is a projector?

So, a projector may be described as an inverted camera, spitting light out of the lens rather than receiving it. For the sake of the following buying guide, we will be considering the 4k projectors, that is, the projectors with video inputs that serves a similar function to the TV or a computer monitor while offering you various benefits, which might include:

  • Larger image sizes.
  • Increased portability.
  • Flexible installation possibilities.

Where does a projector’s light originate?

Projectors mainly use two lamp technologies: metal halide and LED. LED is still not common outside the realm of the pocket projectors. Almost all of the others use metal halide, a form of the tungsten lamp normally enjoying the lifespan of 2000 to 5000 hours if used with the default brightness setting. A handful of the systems use hybrid technologies which augment LED with the laser light source.

What is throw ratio? or Why do screen size and throw distance matter?

Projectors have the main specification which is called a “throw ratio”. Throw ratio is basically the specification which is determined by the first two pieces of the information in an equation.

How far the projector is from the screen (throw distance)? or How wide is the screen?

For instance: Screen Width is 10 feet, Projector-to-the-Screen Distance is 15 feet, then the Required Throw Ratio will be 1.5:1.

Therefore, the first step in choosing the projector, is noting down how wide the screen is and how far from screen the projector can approximately be placed, once you are done with this, your choices will considerably narrow down. Of course, you may still have the flexibility. Maybe your space permits you to mount the projector anywhere you want to on the ceiling. Now in this case, while you might technically be able to choose the projector you want, you should consider mounting your projector as close to the screen as you conveniently can.

Light is subject to the Inverse Square Law, means that the light intensity is inversely proportional to the square of the distance. In layman’s terms, the closer you can mount your projector, the fewer lumens you will need to project the crisp image. At the other point is a case where you have a mount already installed on the ceiling which you want to reuse. And in this case, you will need to find the projector which features the exact throw ratio dictated by the position of the mount relative to the width of the screen.

Screen Size

Projector screens decides the entire buying guide of their own. Though, at this point, many of you will understandably be wondering, “If I’m starting from the scratch, how should I know which screen size to get?” A very rough and quick, rule of thumb is to multiply the distance of the ‘least-favored viewer’ that is, the person farthest from the screen by 1/5. So, if your Least Favored Viewer will be sitting 50 feet away, you will need a screen which is 10 feet high.

But what if you cannot figure out or you do not know? Or what if you are planning to use the projector on the go? Every type of effort should be made to find out, as there is no “standard” throw ratio, nor is there any standard screen size. On paper, the multimedia projectors with the built-in lenses do not appear to vary much. Most of the time they range from somewhere between 1.3:1 to 3:1, whereas the fixed installation projector with an interchangeable lenses might have the lens options ranging from 0.8:1 up to 15:1. You might have decided, as they are all about the same, to risk it. This might work great but remember that even exceeding by only the foot on a 10 foot screen can lead to the critical part of the presentation being cut off.

If you really cannot find out, that you have two options: spring for a model with the more zoom, which will cost you more, or err on the side of the shorter throw. Not the true short throw, mind you, those do not have zoom and they keystone excessively if they are not carefully positioned. But something closer to 1.3:1 end of the spectrum. But why? Because mostly, getting the projector closer to the screen will be less of the problem than getting it farther away. Finally, keep this in mind, that throw is based on the native aspect ratio. If for any reason, you are setting the projector to the narrower aspect ratio than the native, the projector will effectively have a longer throw.

Now you need to consider the following questions before making a purchase to help you with perfect fit for you.

How much brightness do I need?

While throw ratio is important, brightness is the most important specification to start right. And this is where the third piece of the information, the amount of ambient light fits in. If the image is not bright enough to be seen clearly, all of the other considerations fly out of the window. Getting enough light out of the projector is often the biggest challenge, but do not forget that, it is nearly impossible to get a projector which is too bright. If a projector is ever too bright, you can always simply turn the brightness down. But making a projector which is too dim brighter, good luck!

Ambient light normally competes with the projector’s output, causing that image to become washed out. In the perfect world in which we do not live, projectors would always be used in the total darkness. More ambient light you add, the more you lower the contrast and wash out the entire image. Even getting the brighter projector only partially solves the problem, since the ambient light is mixing with darker parts of the image, making them cloudy. If you must use the projector in ambient light, you will never get the perfect image, but it is possible to at least get a viewable image.

Projector brightness is measured in the ANSI lumens (lumens for short). Calculating how many lumens you need requires knowing the image width, throw distance, how much ambient light is present in room, and the content which will be shown. The easiest way to figure this out is to use the projection calculator, a software tool which crunches the number for you. Many projector manufacturers provide you calculators on their websites. If not, then Projector Central is the great resource, and offers projection calculators for almost every projector model made.

Here are some examples of the numbers of lumens you should anticipate needing

  • A living room where the lights can be completely turned off: 1500 to 2000 lumens.
  • A school boardroom or classroom where the lights can be dimmed, if they cannot be fully extinguished: at least 3000 lumens.
  • A lecture hall, churches, or other larger venue, or maybe an environment with the high ambient light: at least 4500 lumens. We have covered best projectors for bright rooms here.
  • A movie theater or a stadium: 20,000 lumens or more.

How it will look if your projector isn’t bright enough?

After looking at the calculator, you may have noticed that the brightness is measured in foot candles. Without the light meter, how is one supposed to know that how many foot-candles of light a room has? Here, a little bit of a judgment and common sense comes into play. Would you consider it ‘well lit’ (50 foot-candles), moderately lit (20 foot-candles), or dimly lit (less than 5 foot-candles)? Or is there the bright sunlight blazing in? If the installation is for the critical viewing, then we would recommend getting a light meter, and then carefully measuring. But for the most practical everyday uses, a rough estimate erring on the side of the too bright should suffice. The content also needs to be factored in.

Are you projecting something white or light colored text over a solid, or dark background? Or are you showing photographs in the art gallery? In the former case, the contrast of your image is so high you can get away with a much weaker projector. But in the latter case, you probably want to preserve every tonal nuance you can and, so, you will need more lumens. If you legitimately have no idea where the projector will be used, then get the brightest one you can afford which you can transport comfortably. However, chances are, that with a bit of thought you can come up with the reasonable estimate of the setting. For instance, if you are a traveling product representative, conducting training with the groups of up to 20 people at different companies, 3000 lumens might be enough if you do not encounter windows without the blinds.

If you do have a room without the blinds, or you are trying to project them outdoors in daylight, be aware that none of the projector may be bright enough. You are asking the projector to do something it simply was not made to do. Finally, if the projector is being used for any type of critical viewing, then it is imperative that the ambient light be eliminated from the setting. If this is not possible, then TV’s or monitors (perhaps arranged as a ‘video wall’) should be used as an alternative. The ambient light not only degrades the image but also alters it, potentially not doing any careful calibration of the projector or the color correction work on the image itself. Projectors probably are not perfect for critical viewing to begin with, but specially not when there is light in the room.

Color Brightness?

Unless otherwise noted, brightness specifications are probably derived from measuring the ‘white brightness’ of the output (ANSI lumens). This can also be misleading, as the way imaging systems render the color images can reduce effective brightness. To provide the more realistic value, some projectors might offer an additional ‘color brightness’ specification. Now that you know that the throw ratio and the brightness, you can consider secondary factors, such as resolution and the contrast ratio.

What resolution do I need?

Resolution matters a lot, but perhaps less than you might think it does. Most of these projectors these days are least XGA (1024 x 768) resolution, a 4:3 aspect ratio format which has been the longtime staple for giving the PowerPoint presentations. A few entry level models are still SVGA (800 x 600 resolution), and the pocket projectors sometimes have funky, and low native resolutions which the manufacturers are coy about admitting. Because of the high definition video, increasingly widescreen formats starting at the WXGA (1280 x 800) and 720p are supplanting the legacy of 4:3 standards. Frankly, we would not recommend going lower than XGA.

At SVGA and lower resolutions, pixilation in the image will definitely be very apparent. Also, many computer programs need at least XGA resolution even to run. You can cheat and set the computer’s projector output to the XGA and let the projector scale image down to its native resolution. Though, the image will look blurry and smaller text will possibly be unreadable. In home theater setups, the screen size to the viewer distance ratio is smaller than for the other applications, here a higher-res image pays off. Otherwise, XGA is most probably fine as a baseline, though going higher than this never hurts. Ideally, we would recommend starting at WXGA and going up from there, not below. Even if you are a PowerPoint user, bumping up to the 16:10 will not hurt, plus, you will be ready if you want to screen HD video down the road. For the special applications, like, exhibiting photos, you will want a higher resolution: at least 1600 x 1200 (UXGA) for the 4:3 or 1920 x 1200 for 16:10 (WUXGA), if not better.

In the case of home theater, it is really a question of whether to invest in the 4K projector or not, since nearly all of the home theater projectors are at least Full HD (1920 x 1080) anyway. If you really want to be scientific about the resolution, a quick Internet search will turn up a lot of resolution calculators into which you can plug a screen size and view distance and the calculator will spit back a resolution. These are amazing but, as with the brightness, the content really needs to be factored in, and a calculator cannot do that. A highly compressed YouTube video may literally look like hot garbage no matter what you try to show it on. While on the other hand, if you are putting together a screening room for the production company, 4K may barely cut it.

Should I care about contrast ratio?

Contrast ratio is possibly the most meaningless specification you will find. Like HDTV’s, projectors rely on so called “dynamic contrast” to boost their paper performance. The dynamic contrast means that comparing the deepest black with the brightness turned all the way down for the image A to the brightest white with the brightness turned all the way up for the image B. Unlike the TV’s, the screen surface plays an important role in contrast. Some of the screens boast high-contrast finishes at the expense of the reduced viewing angles. Moreover, an ambient light will reduce the effective contrast ratio down into the double digits. Under optimal view conditions, high contrast (10000 or more) is a boon. But with more than the trivial amount of ambient light, a 500:1 contrast ratio and a 100000:1 contrast ratio will not yield a visible difference.

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