Digital projectors are the modern replacement to more traditional transparency projectors (OHPs). Transparency projectors work by shining light through a semi-transparent material, such as slides or film. Digital projectors project a digital image directly from a computer or other digital devices through a lens on to a screen. They are of three types - DLP (Digital Light Processing), LCD (Liquid Crystal Display) and LCOS (Liquid Crystal On Silicon).

There is no easy answer to this question of what type of projection systems to purchase. LCDs tend to produce more highly saturated colors and sharper images; most DLP projectors offer deeper blacks and higher contrast. Depending on the resolution and size of your image, you may find LCD screens too pixilated, meaning that you notice each individual point of light. However if you tend to display very detailed images, you may find the softness of DLP projectors to be a problem. As a newer technology, DLP projectors were initially more expensive than similar LCD models, but that difference has largely disappeared. It is recommended that you compare different projection systems with the same brightness and resolution to see which type of projection is best for you.

Portable projectors have features such as small size and lightweight, which make them very convenient for traveling with. Projectors weighing less than 7 Kg are considered to be portable. Projectors in the range of 7-11 Kg are semi portable and above that are meant for fixed installations.

Resolution refers to the number of pixels, or dots, the projector uses to create the image on the screen. Keep in mind that the best resolution for your projector is the resolution of the computer you intend to use with it. If you typically use a notebook computer with SVGA resolution, you will want a projector with the same native SVGA resolution in order to get the sharpest and cleanest image. Similarly, if you normally use a computer with XGA output, you will get the best picture from a projector that has XGA as its native resolution. The more pixels, the "higher" the resolution. In general, the higher the resolution, the more the projector will cost. Following are the types resolution available. VGA (Video Graphics Array) 640 x 480, SVGA (Super VGA) 800 x 600, XGA (Extended Graphics Array) 1024 x 768, SXGA (Super XGA) 1280 x 1024 and UXGA (Ultra XGA) 1600 x 1200

Higher resolution projectors can show small details with more sharpness and clarity.

Illumination is the density of light projected onto a screen or other surface. Projector light output is measured in ANSI (American National Standards Institute) Lumens, or simply lumens. Higher the value, brighter the light output will be. In general, when choosing between projectors with similar specifications, the ones with a higher lumen rating will cost more.

General guidelines: Projectors of less than 800 lumens are good for small groups in conference rooms where the lights are off, or the room is dimly lit. Projectors in the 800 to 1500-lumens range are best for moderate sized conference rooms or classrooms. Lights should be lowered somewhat for best image quality, but ambient light can be high enough to allow people to see one another and interact.

The advantage of a bright projector is that it can be used with the room lights on so people can interact with one another and take notes.

Contrast is the ratio between white and black. The larger the contrast ratio the greater the ability of a projector to show subtle color details and tolerate extraneous room light.

Aspect ratio is the ratio of the width of an image to its height.

Native aspect ratio refers to the aspect ratio of the physical displays built into the projector. A 4:3 display produces an image that is squarer, and a 16:9 ratio produces an image that is more panoramic in shape.

For business uses such as presentations and viewing spreadsheets, 4:3 displays are still your best bet. If you want to watch primarily wide screen DVDs and HDTV movie broadcasts, 16:9 is the right choice for you.

It refers to minimum size of image that can be displayed by projector onto the screen from a particular distance.

The distance that the image can be projected and clearly displayed (in focus).

Brightness uniformity is the percentage of brightness carried throughout a projected image. When image is projected on screen, it is needed to see how brightness is spread on screen, particularly from centre to the corners of image. Brightness should be even all over the image. Some projectors have difficulty carrying brightness to the corners of the screen.

Look for at least 85% or higher uniformity percentage for consitent image quality across the screen which will also ensure fewer hot spots or bright areas on the screen.

This refers to the operational life span of the lamp system in the projector when operated in economical mode or lower setting.

In Eco mode projector is operated on low brightness option but gives enough brightness for desired audience.

Replacing projector lamp is costly affair. So choose a projector with higher Eco mode lamp life, which will save on energy consumption and will prolong the life of projector.

This refers to the operational life span of the lamp system in the projector when operated with full brightness.

In Standard brightness mode projector is operated on optimal brightness option giving higher output than eco mode.

Replacing projector lamp is costly affair. So choose a projector with higher Standard (Bright) mode lamp life.

Digital Zoom facilitates increase or decrease images digitally.

Digital Zoom allows user to select one portion of the screen image and magnify it up to three times its original size from the handheld remote control.

This feature is beneficial for technical or corporate presentations where presenter can visually enhances the presentation content.

A lens with a variable focal length providing the ability to adjust the size of the image on a screen by adjusting the zoom lens, instead of having to move the projector closer or further.

This feature allows the user to place the projector in a fixed location and alter the projected image size by simply turning the zoom lens and then focusing the final image.

Picture-in-picture feature gives presenter utility of two windows for two simultaneous projections. The PIP feature can display more than one window on your screen as a smaller sub-screen.

PIP is useful feature for presentation where in live video projected on one screen along with relevant spreadsheets and figures shown on other screen simultaneously.

Digital Keystone correction feature in projectors allow users to make the projected image rectangular.

Ideally a projector needs to be positioned in level with or perpendicular to the screen in order to get the desired rectangular shape of the image. This feature proves useful when it is not always possible to position projector at right place. It allows images to be keystone corrected to appear rectangular by adjusting and applying digital correction to the image.

This feature is useful if one is required to make presentations at different locations where it is difficult to find the right place to mount a projector.

The Lens Shift feature of a projector allows the optical lens to be physically shifted up and down (Vertical) or left and right (Horizontal) to get images appear in right way from varied locations.

The lens shift feature, sometimes called optical keystone correction, allows the projector to be placed anywhere within its offset range without having any keystone. Lens shift provides space to move the lens itself left and right or up and down within the projector housing. This adjustment can be made either manually with a dial or joystick, or mechanically using the menu buttons. This extra space to reposition the lens means greater freedom in the placement of a projector in a room.

Lens shift feature is better than Digital Keystone Correction because in keystone correction images are adjusted digitally which results in degradation or distortion of images but in lens shift quality of images remains unchanged. It also gives freedom in placing projector anywhere.

It is slot provided on projectors where you can insert PC/flash memory card where presentations are stored.

Memory card reader is of great use for computer-free presentations.

The number of language options that a projector offers for its On-Screen Display. Projectors sets today provide an option of on-screen display in two (Bi-lingual) or many (Multi-lingual) languages.

If you are not comfortable with the language used on the OSD, go in for projectors that support a language you understand.

There are several colour broadcasting systems such as PAL, NTSC, etc. The Projector set is usually compatible to some or all of these. NTSC stands for National Television Standards Committee and PAL stands for Phase Alternate Line.

Choose projector with NTSC and PAL compatibility as it will help you to view general Television broadcast and will also be compatible with other analog video devices.

SECAM (Sequential Couleur Avec Memoire or Sequential Colour with Memory (or System Even Crappier than the American Method ) color TV standard was introduced in the early 1960s and implemented in France.

SECAM uses the same bandwidth as PAL but transmits the colour information sequentially. SECAM runs on 625 lines/frame with the same framerate as the PAL does, 25fps.

SECAM is used in Europe.

HDTV compatible projector is capable of receiving a high-definition television signals (1080i, 720p) with the help of a receiver/tuner.

HDTV compatible projector receives and displays images which has clarity which is better than regular NTSC with around 525 scan line, as HDTV can receives signals which has 1080i and 720p lines of resolution.

Projectors with HDTV compatibility gives pleasure of viewing high quality pictures along with windscreen aspect ratio of 16:9 and digital quality sound which is equal to Dolby Digital 5.1 channel output.

Digital Television, is a new broadcast standard that will provide vastly improved picture and sound quality when compared to the current NTSC broadcast standard of today.

In India beaming of Digital Television broadcast will commence soon. With the help of DTV, viewers will be able see images which have six times better resolution of the their current TVs.

Projector with DTV will be able to receive and display digital signals.

A projector with WiFi or wireless networking allows multiple computer users to wirelessly connect and display the computer information on a screen along with sharing.

Wireless network projectors come with a software and wireless adapter which needs to installed in desired computers.

Network projectors helps in reducing cost by letting multiple users to use, improves efficiency and economical use.

VGA output in digital projector lets user attach other projector or compatible devices to it.

VGA output in projectors are helpful if you are going attach other projector or computer to it, so the video from your computer can be seen through the other projector and on a monitor of other computer at the same time.

DVI stands for Digital Visual Interface. This is digital connection unlike analog VGA available between display source and computer along with other DVI compatible devices like DVD Player, Digital Satellite or cable TV box etc.

For devices that support DVI, a digital-to-digital connection can be made that eliminates the conversion to analog and thereby delivers an unblemished image.

HDMI (High Definition Multimedia Interface) is a new connectivity standard that carries high definition audio and video signals on the same cable.

it is a digital cable and connection that supports digital data transmission. Unlike DVI, which supports only video transmission, HDMI supports both high definition video and audio.

HDMI is superior to DVI. HDMI supports standard, enhanced, or high-definition video, plus multi-channel digital audio, and interactive controls on a single cable. It transmits all ATSC (Advanced Television Systems Committee) HDTV standards and supports 8-channel digital audio.

For projector operation, the USB is commonly used to connect a remote mouse.

It facilitates to connect your USB flash drive to display your presentations, pictures and documents. It allows Computer-free playback.

Digital projectors with Component Video inputs have 3-jack connection, which facilitates the ultimate in color accuracy with a Component Video Output compatible DVD Players and other devices, and virtually all of todays DVD players include it.

Component inputs are the best video inputs available for projectors. They separate the video signal into 3 component parts, and improve resolution, picture detail, and have great color accuracy. A single component video input includes three RCA jacks — one for the brightness (luminance) section of the video signal, and two for the color (chrominance) section. Due to these separations in component video connections, they offer even higher-quality video transfer than S-video connections, with improved color accuracy and less bleeding.

Component video inputs in Digital Projectors help you to connect latest DVD players, gaming consoles and other devices giving higher resolution output.