LCD    DLP    SXRD Type.
Resolution    Aspect Ratio
Screen Size    Brightness    LampLife
Throw Ratio    Contrast Ratio    Lamp Power
End Use : Home , Business , Classroom
Must know before buying a Projector
By Ravindra Johari
Mar 15, 2017
Here are the things to decide before buying a Projector:
Space availability for projection. This one single need would determine Screen Size that in turn decides specifications like F-Number, Focal Length of the Lens and Throw Ratio.
Once the minimum and maximum Screen Size is fixed, the next thing to decide is the selection of the kind of technology considered suitable for your application viz LCD, DLP and SXRD type projection. We discuss the construction of each at the end of this article and the pros and cons of each type. Let's discuss the key considerations here.
1. Focal Length, Zoom Factor and Throw Ratio of the Lens.
These specs define how far and near from screen the Projector can be placed and the possible screen sizes.
The Throw Ratio that is the Ratio of the Screen Size to the Throw, the distance of the Screen from the Projector has to be looked at, depending on the availability of size of the room for Projection. For instance, a classroom with space constraints would need a projector with short throw or Ultra short throw sufficing to the required screen size, while a Large Venue Projector would require a Larger throw catering to a much bigger screen size. The Screen Size spec is mentioned by the manufacturer, yet the distance of the Screen from the projector is what is defined by the Throw Ratio.
2. Brightness and Contrast Ratio
The light that projects on the screen is sourced by a Lamp, processed to a billion or even a trillion colors before reaching the Projector Lens and then thrown on to the screen by the lens. But what defines the brightness and the variations in the bright and darker regions? The brightness is determined by the number of lumens the lamp is able to supply before it passes through the lens. the higher the lumens, the higher the brightness and higher is the power consumption requirement to generate that level of brightness.
Contrast Ratio defines maximum whiteness to maximum blackness. The more this ratio, the better it is in realizing whites whiter, grey grayer and black blacker.
XGA, WXGA, FHD, WUXGA, 4K all relate to the number of pixels available to reproduce the image to be displayed on the screen and the proximity of pixels from each other.
The higher the resolution the better the picture realized at a granular level. Number os pixels and resolution of 4K > WUXGA > FHD > WXGA > XGA. Selection should be determined based on the requirement like the one needed for home theater would go with 4K or FHD and the one needed for Classroom would suffice with XGA or WXGA.
4. Lamp Life and Lamp Wattage.
This specification determines how long the Projector Light Source can run before demanding a replacement. Multiple values of Lamp Life in hours is specified by the manufacturer for Normal modes, Eco modes and other modes specific to manufacturers. These modes usually have a dimming effect on the light out resulting in the saving of Lamp Power there by resulting in an increase in hours of lamp Life.
Projectors come with multiple ports and not limited to HDMI IN for connecting a source through HDMI , HDMI Out for connecting a television HDMI IN for example , Plug and Play with USB2 , LAN port, Monitor Out , VGA , MHL for direct connectivity with Mobiles/Tablets , Audio/Video In, Audio Out and inbuilt speakers ranging from 2 Watts to as much more than 20 Watts.
Choose based on what all you intend to connect to the projector. The Wireless option provides an option to display content to the screen wirelessly.
6. Power Consumption and weight.
Not a main consideration, yet an important one. Look for a projector that suffices your requirement with minimum wattage consumption and less in weight.
You might need to look at weight depending on whether it's a fixed installation Projector say for a conference room or a portable one.
DLP and LCD Type Projector :
DLP Type: All technologies use lens for projecting , however the difference is how white light reaches the lens and the processing of light before it reaches the lens.
In a DLP type, white light is made to pass through reflective mirrors contained in an IC called DMD or Digital Micro Mirror Device that acts as a light switch. These swiches are away from the light source to produce different shades of grey. In a single chip DLP system a color wheel is added to convert this white monochrome light to Red, Geen and Blue sequentially to fall on the DMD Chip creating a billion colors with the on and off sequence. In a 3 chip DLP system white light passes through a prism dividing it into Red, Green and Blue. one chip is associated with each color and the reflections from the Red, Green and Blue chips are combined and passed through the lens producing more than a trillion colors.
LCD Type: In a LCD Projector, Light is made to pass through polysilicon LCD to the lens. The LCD consist of crystals sandwiched between two polarizer sheets. The LCD is backlit with red, Green and blue light. Where the DLP is made up of reflective mirrors, LCD is made up of tiny cells. The opacity of the cells is controlled by an electrical signal that controls the properties of the LCD Panel. In a 3 chip LCD system Light passes through Red, Green and Blue Mirrors before being polarized by the LCD.