In the world of image projection, video projectors certainly take first place on the podium. Previously intended for the professional field or for large-scale presentations, they have now been democratized to equip many homes. From showing films in the living room to video games, video projectors are perfectly suited for home use. One of the conditions for making the most of this technology is knowing how to place your device optimally in relation to the screen.
A video projector is defined as a projection device intended to reproduce a video source on a separate screen or on a white wall surface via a system of lenses. As such, it must be differentiated from overhead projectors which have an already integrated optical display system. A video projector is first defined by its technical characteristics which, once established, are used to determine the optimal placement position.
There are several projector technologies and each depends on the intended use. They can be broadly classified into three categories. First, DLP (Digital Light Processing) technology ), which projects the input image through the light source, a reflection system based on mirrors (each pixel is actually a micromirror) then makes it possible to reconstruct the colors. This is the most widespread technology.
Then, the tri-LCD technology, based on a system of three LCD screens to reconstruct the image. The brightness is often stronger and the range of colors more natural (to the detriment of the contrast ratio), thus allowing projection in a lit environment. Finally, LED technology, widely used in screens and televisions, incorporates more advanced laser lamps than the UHP lamps of DLP and tri-LCD, thus allowing quieter operation of the device.
Projectors are also characterized by four main technical characteristics. First of all, the luminosity (expressed in lumen) is the light intensity delivered by the device. If in very dark projection environments an average brightness (2500 lm) is sufficient, in bright environments it must be high or even very high (more than 5000 lm). So, depending on the model, the price of a projector lamp can vary greatly when it comes to making repairs.
Then, the contrast (expressed in lux:1) is an essential property in the choice of a video projector. The higher the contrast, the greater the chromatic saturation and the more pronounced shades of black, thus generating more and more beautiful images. Good contrast is defined by a value of 5000:1 in the low range. Then comes the definition (expressed in pixels); the higher the number of pixels, the sharper and more precise the images will be. It scales according to the source and the aspect ratio.
Finally, the sound level (expressed in dBA) generated by the ventilation system of the device (generally one or two fans). In everyday use (games and movies), a maximum noise level of 28 dBA should not be exceeded, with an optimal level between 22 and 25 dBA. In addition to these technical characteristics, it is also necessary to size your video projector according to the place where it is intended to be installed.
Having a projector that meets your technical needs is a good start, but it is not enough. The intended location of the device should also be considered when choosing. Indeed, a device placed too close to the projection surface will display a blurred or poorly contrasted image. Conversely, if it is placed too far from the projection surface, the light will undergo a strong dispersion and the image will be partially or totally lost.
Before determining the ideal placement distance, the brightness must be correctly determined. The larger the target screen size, the higher the brightness will need to be. Similarly, very good brightness is required when the projection takes place in a lighted environment. Different manufacturers offer lamps according to the needs of the users. For home use, for example, the Vivitek projector lamp is a good component.
Then, to calculate the ideal projection distance, a simple calculation involves determining the throw ratio. It is the ratio between the projector/screen distance and the width of the screen. This data is often specified by the manufacturer. So, if you have a 1.8m screen with a throw ratio of 1.5, the 1.8 × 1.5 calculation gives you the distance to place your device. In this case, 2.7 meters.
Conversely, if you have already determined the projection distance (fixed position) and want to find the corresponding projector, there too the calculation is simple. If you have a 2m screen for a screen distance of 2.5m, the 2/2.5 calculation gives you the throw ratio you will need to look for. In this case, it is 0.8.
