By Andrew Ghigo

Today's compact yet powerful front video projectors may leave you with a too bright an image to watch! This being especially so if you intend to watch a projected image in a darkened room – which after all, is most often the case with a home theater setup.

Defining ‘Screen Gain’

Prior to proceeding with our discussion, it is important that one has a full understanding of what the term ‘screen gain’ is all about.

It may sound strange that we talk about ‘gain’ when in reality a projector screen is nothing more than a passive device. Yet there is - it is all a question of how the screen surface distributes the reflected light.

Screen gain is a measurement of the reflectivity of the screen surface. It measures the ability of the screen to direct incident light back to the audience.

The gain number represents the ratio between incident light and reflected light. A flat matte white surface has a gain of approximately 1. A gray screen has a gain less than 1 and therefore, it attenuates incident light. Reflective screen surfaces have gains greater than 1; these projection screens direct more incident light back to the audience.

Gain is always measured in front and perpendicular to the screen at the point of maximum brightness; this represents peak screen gain and occurs at the zero viewing angle perpendicular to the screen surface.

For a screen with gain greater than one, the gain drops as one moves to the side and view the screen at an angle to the perpendicular drawn from the center of the screen. The angle at which screen gain falls to half the peak is referred to as ‘half gain viewing angle’. A person viewing the screen from this angle will see the image half as bright as the person seated at the center. The more one moves further away from the center, the dimmer the projected image will be.

The higher the peak screen gain, the narrower the supported viewing angle. This is the price one has to pay for a higher screen gain - the higher projector screen gain at the center is in fact achieved by directing more light towards the center viewing positions rather than allowing for a uniform reflected light over a wider angle of view.

Projected Image Brightness:

Matching the projection screen gain with the ambient light and the video projector output is essential if you want to ensure that you will end up with a correct level of projected image brightness.

This is an extremely important issue. Do not forget that a basic requirement for a great movie experience is a comfortable environment. This means that the time one spends watching a movie should be as comfortable as possible. Exposure to a bright projected image is uncomfortable on the eyes - even when this is for just a few minutes, least imagine when watching a two-hour movie.

A Tricky Matching Process!

Ambient Light Conditions, Image Brightness & Screen Gain

A projected image is at its best when viewed in total darkness - this helps take away any visual distractions - rendering it easier for the viewer to get deeper immersed into the movie action.

In the home, achieving a completely darkened room is almost impossible except in the case of the dedicated home theater setup. The amount of ambient light present has an impact on the resultant projected image contrast. This calls for the need to increase the image brightness to maintain the correct level of image contrast.

The tricky issue is to arrive at the correct level of image brightness for a pre-set level of ambient light. This in view that projected image brightness is a function not only of the projector output, but also of the screen gain, and image size.

The explanation that follows should help you get a better understanding of the relationship that exists between these three inter-related parameters.

Display Brightness and Screen Gain

The brightness output level of your projector is a measure of the projector output power in terms of light intensity. Please keep in mind however that the resultant projected image brightness is a different issue. Image brightness falls in proportion to the area of the projected image size - the bigger the projected image is, the dimmer it will look for a fixed level of projector brightness.

The projected image brightness - more specifically the Luminance level for a projected image, is a measure of the light reflected from the projector screen area. It is measured in foot-Lamberts, and is defined as:

ANSI-lumens of your projector divided by the square footage of Screen.

(Note that one foot-Lambert is equal to 1 ANSI lumen per square foot.)

To arrive at the actual level of light reflected from the screen surface, the above result must be multiplied by the projector screen gain.

A useful reference here is what has been defined as ‘sufficient brightness’ by the Society of Motion Pictures and Television Engineers, also known as SMPTE.

In standard 196M, the SMPTE determined sufficient brightness for showing motion pictures in a darkened room using a unity gain matte white projector screen, as 12 - 22 foot-Lamberts. In practice, the luminance target level is set to about 16 foot-Lamberts, while the average bright scene brightness level in a movie theater is typically 60% to 75% of this target value.

Display brightness is in itself an entirely subjective term; what’s more, it is all relative to the amount of ambient light falling on the screen surface.

The following rules of thumb would surely come to assistance in this respect:

1. The contrast ratio between the projected image and the ambient light level falling on the screen should be at least 5:1. This is necessary for the eye to perceive a real impression of brightness. If this contrast ratio is not achieved, the projected image will not be considered of adequate brightness level.
   
   

2. When viewing takes place under normal ambient light conditions, the luminance level should be close to 50 foot-Lamberts. This level of luminance is derived from the fact that SMPTE indicated a target level of image brightness for a CRT TV as 50 foot-Lamberts, this in view that a TV is normally viewed under normal ambient light. One may argue that TV is a totally different technology – this is true, but this target level for image brightness or luminance, still holds good for most circumstances.

How does all this translate in practical terms?

If one is viewing an image in typical very low ambient light conditions (say less than 2 foot-candles - equivalent to approximately 22 Lux), then the minimum required light level ‘illuminating’ the screen surface should be around 10 foot-candles to achieve sufficient image contrast.

For a matte white projector screen surface with a screen gain of one, this translates to a minimum of 10 foot-Lamberts in terms of light ‘reflected’ from the screen for image brightness. This is close to the SMPTE typical requirement for average luminance when viewing pictures in a darkened room.

Similarly, if viewing were to take place under normal ambient light room conditions (typically 10 foot-candles or 110 Lux), applying our first rule of thumb to achieve the required contrast level would result in a luminance level of 50 foot-Lamberts (approx. 540 Lux) for the same matte white projector screen surface. This is also in line with the target luminance level detailed in rule 2 for viewing under normal ambient light conditions.

Note:

• Light illuminating a surface is measured in lux (Lx = lumens/m2), or foot-candles.
• Light reflected from an area (luminance) is measured in candelas/m2 (cd/m2) or foot-lamberts (fL).

Now, let’s consider as an example what will happen with different projector screen gains for say a given 1000 ANSI-Lumens projector and a 100" diagonal screen size.

Projector Screen Gain 1 1.5 2 Image Luminance in foot-Lamberts 30 45 60

It is clear that our 1000 ANSI-Lumens projector would produce a too bright an image when the latter is viewed in a darkened room, even when using a standard matte white projector screen with unity gain. Similarly, use of this projector in conjunction with a projector screen surface having a gain of 2 may result in a too bright an image even when viewing takes place under normal ambient light conditions.

Andrew Ghigo – A Telecoms/Electronics engineer by profession, with specialization in digital switching and telecoms fraud management systems.

Editor and publisher of http://www.practical-home-theater-guide.com - a site dedicated to all home theater enthusiasts with the scope of serving as a comprehensive home theater guide to home theater systems, product reviews and home theater design.

This article is an excerpt from a series of guides appearing under the home theater screens section of the site.

Article Directory: ArticleSlash.net

By Kalon Willis

The measure of a man's success depends on the things he holds of value. In most cases this means the things he loves the most. Accumulated property has always defined a man. Nowadays, the things owned need not be of use to be considered valuable. From home appliances to home theatres; demand is always higher than the supply in order to keep people buying. However, the situation is not all gloomy. Never in the history of mankind have so many products flooded the consumer market with the sole intention of making life as comfortable as possible. For any man with a sizable ego, the size of his screen when watching that champion league's match is vital. Men enjoy showing off their electronic appliances and what better way to do that than by owning this home theatre projector screen with 92 inch pull down capability.

Imagine a screen large enough to flood your living room with so much light when turned on that you do not need makes use of a light bulb. A screen you can effortlessly move from one point in your living room to another because it is light in weight. You do not have to imagine, the home theatre projector screen is all this and much more.

The home theatre projector screen provides clearer images from your projector like never seen before. It is the latest in high quality chinese technology with the highest quality matt white surface in the industry. The image size it supports is incredible:1.140m in width by 2.03m in height! It would be very imposing in any room. This device comes in quality casing with an easy to install roller mechanism and a firm locking mechanism as well for the convenience of the consumer. This screen can easily be used in community events or as a cinema projector for those with an entrepreneurial mind.

The home theatre projector screen is relatively light - at about 15 kgs making it one of the largest semi-mobile screens in the world. This device can be used by organizations and households alike to showcase whatever material they have. In situations like where a humanitarian group wishes to educate a large gathering of people quickly or even at once, this device can prove the lifesaver with the ability to be viewed by a sizable gathering either indoors or outdoors. The quality of the device compared to others of similar make is unrivalled with this device providing better pixel quality than even the Samsung projectors.

The home theatre projector screen is sold on the online electronics store, electroniconnection.com at the asking price of $279. This price is relatively lower than most other firms given they range to about $300. In fact, by 11th july, the store was already almost out of stock with new orders coming in from around the country and abroad. Thus far, feedback received by the firm from all consumers has been incredibly encouraging with new supply coming in with more screen size options from 82 to 120 inches.

Kalon Willis
University of Findlay/College of Business
CEO/ Founder of ElectroniConnection.com
ElectroniConnection@rocketmail.com
http://www.ElectroniConnection.com
Here at ElectroniConnection.com, we sell every kind of name brand electronic you can imagine at the lowest prices possible. Everything in our webstore includes Free Shipping and great customer service from our loyal employees. Come and visit us soon!

Article Source: http://EzineArticles.com/?expert=Kalon_Willis

See a large Selection of Home Theater Screens Only Here!

With the rising popularity of the use of projectors and fixed projector screens in home theaters, the market for both of these items has become fairly competitive.

If you are setting up a home theater and you are planning on using a projector and screen, there are a few options worth considering beforehand.

First of all, regarding the projector, it is possible to find very good refurbished projectors that come complete with guarantee, for an exceptionally good price online, and quite possible at your local home theater accessory shop as well. If cost is an issue for you, you will be happy to hear that you can buy a refurbished projector and screen for less than you would pay for a large LCD screen. The quality is comparable these days, and the only drawback really is that you need a totally dark room for viewing when you use a projector and screen.

The next choice you will be faced with is whether to buy a fixed projector screen or an electric projector screen. There are pros and cons to both. Again if price is an issue and you can place the screen in a room that does not get a lot of traffic but is used primarily as a home theater for viewing, then you may find the fixed screen is the way to go.

Some of the more popular brands of fixed projector screens include the Elize ezFrame screens, the Da-Lite Cinema Contour screens and the Maxstar Premier series. Elite and Draper projector screens are also fairly common and popular. Each brand has its strengths and weaknesses, and basically with each type of screen you get what you pay for. If you are willing to pay more, you will generally get a screen with more options and better visibility.

The one exception to that is the Da-Lite Contour series. This screen has all of the options of the more expensive screens, yet it is one of the more reasonably priced. Screen size ranges from 60 to 220 inches and they have both video and HDTV format screens. They have perforated screens, which allow you to place speakers behind the screens. If decor is a problem, they also have a variety of different framing possibilities including a wood grained type frame that would fit in well with most home furniture.

When looking for a fixed screen projector, remember to compare features as well as prices, before making your final purchase.

Click Here to discover more about fixed projector screens.

Wai Lan has been involved in the electronics industry in Asia for many years, and is thoroughly familiar with the production and marketing of fixed projector screens, and the cheap projectors.

Article Source: http://EzineArticles.com/?expert=Wai_Lan

Even though manual projector screens are usually affordable, they can still cost quite a bit of money, especially if they are 100'' or wider and of high quality. And this is why you wouldn't want your screen damaged.

Is it better to keep the manual projection screen rolled out at all times or should it be rolled in?

Keeping the screen rolled out is obviously the easier option and it also makes sense since if you keep rolling it in and out all the time, you might damage the screen. However, there are circumstances when you would want to keep the screen rolled in and some of them are listed below:

Protect your manual projection screen from direct sunlight. Direct sunlight is likely to damage your screen in the same way that it would cause a photograph to fade; when kept close to a large window and exposed to direct sunlight for a long period of time, the screen fabric will start turning yellow. Of course, this is a slow process, but in a brightly lit room you would want the screen rolled in.

Protect your manual projection screen from cigarette smoke. The cigarette smoke damages the screens pretty much in the same way as the direct sunlight - the fabric will also gradually turn yellow and you will see the picture quality deteriorating.

Protect your manual projection screen from getting damaged by your pets or kids. If you have young kids or pets in your house, keeping your screen rolled in at all times is the only way to protect it from being torn or damaged.

Click Here to see some high quality manual projector screens that are more resistant to your typical damage.

http://www.projector-screens.biz/projector/1/Keep-your-manual-projection-screen-rolled-in

Article Source: http://EzineArticles.com/?expert=Peter_Kerl

Since I was a child, I always dreamed of the day when I can have a home cinema projector set up in my home. I wanted to have the biggest home theater screen possible, then I realized that there is more to buying a home theater projector than just screen size. So I would have to say that the first thing to consider when your looking for the best home theater projector for the money is how and where you will be using it.

Using Projector for Movies and TV:

Regular large screen flat-panel TVs are nice, but sometimes they just aren't enough for those with a high quality big picture appetite. HDTV home theater projectors give you an engaging viewing experience by projecting wide-screen video in high definition directly on a wall or on a HDTV projector screen. If you intend to watch high-definition television programs via your cable television or satellite service provider, a HD home theater projector will work and look great. There are many manufacturers who now offer 1080p HD projectors that will suit your home theater needs. Some of the better known makers are BenQ, InFocus, Panasonic, Sharp, Optoma, Mitsubishi, Proxima, and NEC.

Using Projector for Work and Presentations:

If you're a professional who needs a visual aid for presentations and lectures, then multi media projectors will be ideal. Most projectors have inputs for laptop computers, SDTV, HDTV, DVD/Blu Ray players and/or VCRs. These type of projectors can reproduce audio, various video formats, and presentations based on text and images. Unlike home theatre projectors, multi media projectors are smaller and more practical for easy carrying. There are quite a few that also include a carrying case to prevent damage and ease transport. They also have a remote control and a built-in laser pointer, this allows you to have more flexibility and the freedom to move about. If you intend to use a multi media projector to watch movies, make sure it's adaptable to home theater systems.

The Various Projection Technologies

To project light and colors to make clear and visible images, projectors use either LCD technology (liquid crystal display) or DLP (digital light processing).

A LCD Video Projector displays presentations that are dynamic and crisp. LCD video projectors passes light through three small LCD panels, creating radiant images and are ideal for rooms with soft lighting.

A DLP Video Projector use a single digital chip that makes them weigh less than LCD video projectors. These devices offer invigorating video performance, high contrast ratios, and reduced breakdown in pixels. This is what make DLP technology perfect for home theater setups.

These are just a few of the things to take into consideration when you are trying to decide what type of projector to get. If you want the biggest screen possible for your home cinema, a DLP home theater projector would work best. If your intent is to use it for business meetings and presentations, then a LCD multimedia projector would be fitting. However, a dlp multimedia projector is also an option. I hope this will help you make a more informed judgment.