In order to decrease the immediate cost, some customers opt to project their image onto a plain wall which will definitely get you an image but image quality will never be as good as when a good quality projection screen is used. Painted walls, even if painted white, will not match the color reproduction, brightness efficiency, and overall image quality of a good quality projector screen. To get the best performance out of your projector, we always recommend the use of a projector screen.

All display devices like Projectors, TVs, Monitors have an aspect ratio i.e. the shape of the projection. There are 3 aspect ratio commonly used, 4:3 (i.e. more square), 16:9 and 16:10 (which are both widescreen formats). We recommend you to use the Projection screen of the same ratio to the Projector you are using. If you have a SVGA or XGA resolution projector, that would be 4:3 ratio so best to use 4:3 screen. If you have a WXGA resolution projector, that would be 16:10 ratio so best to use 16:10 screen. For Home Theater where you have a Full HD resolution projector, that would be 16:9 ratio so best to use 16:9 screen.

There are various types and qualities of Projection screens availble in market. Following are the details which you can refer as a guideline to buy one.
Front Projection Screen
Front projection screens are generally available in 3 styles- Pull down screen, Tripod Screen, Fixed Frame Screen
Pull Down Screen (Manual Screen, Instalock Screen, Motorized Screen)
These types of screens are most popular and better for general activity areas like education & corporate where the screen can roll down for use and disappear when not in use. Manual Screens are operated manually and are considerably cheaper than any other screens. Motorized screens are electrical screen which comes with pull up and down button remote control.
Tripod Screen
Tripod Screen works same as manual screen. The benefit with this type of screen is that it comes with tripod stand which makes it completely portable that can be useful for people who don’t want to fix it on wall and willing to carry with them.
Fixed Frame Screen
Fixed frame screens are generally better for dedicated viewing areas like Home Theater because they are having permanent fixtures which look alike Large TV/ Monitor.
Rear Projection Screen
Rear Projection Screen are used for enhanced contrast and brighter images and best suitable for stage application where you don’t want shadow of the presenter on screen or casting viewers on the screen or where you want to hide the projector behind the screen.

LCD ("Liquid Crystal Display") projectors contain three separate LCD glass panels, one each for the red, green, and blue components of the video signal. The pixels in each panel contain a liquid-crystal material that regulates the amount of light passing through them by twisting and untwisting in response to electrical voltages. After exiting the LCD panels, the three colored beams are combined by a prism and projected onto the screen by a lens.
DLP ("Digital Light Processing") is a proprietary technology developed by Texas Instruments. It works quite differently than LCD. Instead of having glass panels through which light is passed, the DLP chip is a reflective surface made up of thousands (or millions) of tiny mirrors. Each mirror represents a single pixel. To define color, a color wheel is used that contains (at minimum) a red, green, and blue filter. This wheel spins in the light path between the lamp and the DLP chip and alternates the color of the light hitting the chip from red to green to blue.

Contrast Ratio is how far the Whitest white is from the blackest black. Higher the contrast ratio means better picture quality. A contrast ratio of 500:1 means that the blackest black on the image will be 500 times darker than the whitest white. The contrast ratio matters most for home theatre or when you wish to project in a darkened room.

The best answer to this question is which quality picture you would like to have. Many people do not really consider the importance of having the right inputs. The hierarchies of video quality are as following:
Best Quality: Digital High Definition Video – HDMI or DVI
Good Quality: Analog High Definition Video - VGA (15-pin D-sub), BNC
Low Quality: Analog low Definition Video - S-Video or Composite Video

The brightness of the projector indicates how brighter the image will be projected. The brightness of projector is measured in ANSI lumens.
Home theatre projectors will range from about 2000 lumens up to about 3000 lumens brightness. When you're watching a movie you will most likely dim most of the light from the room, so a bright projector is not only unnecessary it will be overpowering in a dim room. Home theatre projectors generally focus on providing high detail, accurate colours, and high contrast to give the best picture possible.
Presentation/ Training room will require from 3000 to 5000 Lumens brightness. This will ensure that the image is visible on the wall/screen in most lit rooms. Just remember the larger the screen and the brighter the room the brighter the projector will have to be. 3000 lumens is usually enough for a boardroom sized area, while 4000+ lumens is better for small halls or classrooms/areas with lots of natural light.
Larger venues presentations with a lit room/hall, we would recommend 4000 lumens and above. The larger the screen has to be and the more light that comes in the brighter the projector will have to be. For a 2m wide picture in a well lit room 4000 lumens is normally fine, for a 4m wide picture in a well lit room you would be best to jump up to around 6000 lumens or higher.

The resolution is the number of pixels being projected on a screen. The most common measurements of resolution for projectors are:
SVGA - 800x600
XGA - 1024x768
WXGA - 1280x800 (HD)
WUXGA - 1920x1080 (Full HD) or 1920x1200