A Buyer’s Guide to Business Projectors - Knowing the Specs to Choose the Ideal Business Projector

The principle behind projection distance is that the shorter the projection distance (1) the greater the number of lenses needed, (2) the higher the complexity of the projector design, and (3) the lower the yield; all resulting in a higher price for the projector. Below is a list of projector types, in terms of projection distance, and their suitable settings:
• Normal: Conference Rooms, Classrooms
• Short Throw: Exhibition Spaces, Simulation Space, small class room / conference room
• Ultra Short Throw: Interactive Projection Spaces, Interactive Classrooms

The sections below will help describe throw ratio, zoom ratio, and lens shift, as well as describe their differences.

• Throw Ratio
Throw ratio is the distance from the projector lens to the screen divided by the screen width. For a fixed screen width, the shorter the projection distance the smaller the throw ratio, which is the case for short throw and ultra-short throw projectors and vice versa for long distance projectors.

• Zoom Ratio
If a projector is designed with a built-in zoom lens, it will be able to adjust the size of its projected image from a fixed position without having to move the projector. Zoom ratio is then defined as the ratio between the width/length of the largest image the lens can produce from a given position and the width/length of the smallest image the lens can produce from the same position. In terms of real world application what this means is that given a fixed image/screen size, the larger the zoom ratio, the larger the range of distance the projector can be placed from the screen. Thus, the larger the zoom ratio the more flexibility you will have in terms of installation options. In this scenario, as seen in the image below, the zoom ratio is equal to the Da divided by Db (where D is the distance between the projector and the screen).

• Lens Shift
For most users it’s quite difficult to get the projected image to be perfectly centered on the screen during the installation process. A lot of the time the projected image will fall either above or to the side of the screen, while trying to perfectly center the image on the screen solely by means of moving or adjusting the projector itself hardly ever works. Because of all this lens shift is a must-have feature for projectors. Its vertical shift allows the projector’s lens to shift in order to move the image up or down, while its horizontal shift allows the lens to move the image left or right. Most projectors feature hardware controls on the projector itself that allow users to perform the lens shift function, while some high-end projectors allow you to use the lens shift function via electronic controls or the remote control.
Using the BenQ LK953ST model projector projecting a 100-inch image as an example, its vertical shift has a range of 60% (60% of the height of the image) while the horizontal shift has a range of 23% (23% of the image width), as seen in the image below.

• Keystone (Vertical Keystone, 2D Keystone, Auto Keystone)
When a projector is installed in a location/orientation that prevents it from being properly aligned to the center of the screen the projected image will be distorted into a trapezoid, this is called the keystone effect. For instance, if the projector is installed above the screen and is tilted down when projecting, the image will have a keystone effect along its vertical axis, if the projector is even with the screen but off-center horizontally the image will have a keystone effect along the horizontal axis. The reason why this happens is because the projected image is not properly projecting onto the plane of the screen at the required 90-degree angle. The following are descriptions of the different type of keystone corrections available on projectors:

o Vertical Keystone: The most basic keystone correction. Currently 4K projectors only support vertical keystone because of limitations in their circuitry.
o 2D Keystone: Supports both vertical and horizontal keystone correction.
o Auto Keystone: High-end projectors feature auto keystone correction where a G-sensor is embedded into the projector allowing the projector to automatically correct for the keystone effect via a hard key or the projector’s OSD menu.

Rec. 709
Rec. 709 is a standard set by the International Telecommunication Union (ITU) for HDTV that includes the Rec. 709 color space which is identical to the sRGB color space. All High-Definition TVs and projectors should be able to cover 100% of the Rec. 709 color space.

Before discussing LAN control, we must first understand what LAN means. LAN, or Local Area Network, means a group of computers in the same area interconnected to create a closed network. This network can be made up of two computers in the same office, or it can be populated by the thousand or so computers in a large company. The average company uses LAN to setup its network so that the users in its network can communicate electronically and transfer documents. In terms of projector use, all you have to do is connect the projector’s RJ-45 port to the network and set up the IP address (via the IP address capabilities of a LAN network) to be able to control the projector via LAN.

With the RS-232 standard, characters are transmitted via a string of bits strung into a serial sequence. The advantage of this type of transmission is that the lines needed to transmit the signal are few so the cables used are simpler. The disadvantage is the transmission range is shorter than network cables, so for control over long distances LAN control is recommended. BenQ projectors support the two RS-232 interfaces shown in the image below; the user manual for a projector model will indicate which specific interface it supports.