1- For which use?

If video projection immediately evokes "home cinema", video projectors can be used in other contexts. These different uses correspond to different types and formats of material. In the first place, it is therefore necessary to determine what will be the main use of the video projector.

•Home cinema

In order to obtain the best possible image on a wide screen, the higher the resolution, the better. You can turn to Full HD (1920 x 1080 pixels), or even Ultra HD (3840 x 2160), in particular to enjoy contents on UHD Blu-ray Discs,  or series and films broadcast in this format, or via video on demand. For home cinema use, high contrast (at least 2000: 1) should be preferred over high brightness for better rendering, and it is essential to be able to darken the room. In this context, a brightness of 1000 lumens is sufficient but a high lamp mode (more than 1500 lumens) can be useful for other uses. The connection will be via HDMI to connect to a player or a TV box. In Ultra HD, the HDMI 2.0 or higher standard allows a high speed of 60 images / second.

Regarding the designation 4K, manufacturers sometimes incorrectly call 4K what is in reality Ultra HD (3840 x 2016). True cinema 4K resolution is a bit larger, with an aspect ratio of 4096 x 2160 pixels. This difference is found in video projectors, with 4K cinema models being much more expensive.

•Video games

A video projector allows you to fully immerse yourself in a video game thanks to the large image size and the fact that you can get close to it. The PS4 Pro, PS5, Xbox One S and X consoles are capable of delivering Ultra HD display and some games are now natively formatted, and others will be upscaled. However, a projector adapted to video games and to this format is expensive. You could be fully satisfied with a Full HD model, which is sufficient for older gaming consoles and most video games anyway. It is often considered that a good video projector for home cinema is a good video projector for gaming. This is true of the picture quality, but the latter should also be responsive enough so that there is no lag (latency) between player actions and display. For this reason, some video projectors have a gaming function. This is particularly to be checked on wireless projectors, which are very practical to avoid cables, but sometimes not very responsive. For video games, brightness is more important than in home theater because many games are very dark and you will often want to be able to play without obscuring the room.

• Office

For projecting documents and worksheets, you don't need exceptional display quality other than sufficient contrast. The important criteria are the possibility of projecting without great recoil (short focal length) and the presence of a connection allowing to connect easily to a computer, a tablet or a smartphone, while knowing that an HDMI socket may be sufficient because there is then adapters to all other formats. It will also be possible to gain more ease of use during presentations if the equipment has a remote control which is very practical. These light and affordable projectors, on the other hand, are not very appropriate for video contents and are especially designed for still images when presenting documents. Brightness is also an important criterion to avoid having to darken the room.

• “On-the-go”

Recently, we find devices called "pico-projectors" that can be held in the hand. Such projectors are quite suitable for office automation. With a resolution up to Full HD (1080p), they can also be taken to your vacation spot to watch videos. A true technological feat, unimaginable not long ago, the pico-projector is currently intended for projection on small surfaces. With an image size of 100 cm ( 39 inches / 3,3 feet ) diagonally, they should rather be considered as a substitute screen. Some pico-projectors operate on battery and are therefore independent of any power outlet.

2- Different technologies

The image projected by a video projector uses various display technologies. The main ones are DLP, LCD and Laser. A technology derived from DLP, called LCoS, is found in manufacturers like Sony and JVC. Named respectively SXRD and D-ILA, they combine the advantages of DLP and LCD but are also more expensive.

• DLP technology

Based on the use of a matrix composed of micro-mirrors, DLP (Digital Light Processing) chips are commonly used by many manufacturers. You will appreciate deep blacks and excellent overall sharpness, in particular due to the absence of motion blur which will delight video game enthusiasts. Images from this technology are flattering, natural and contrasting, but sometimes suffer from a lack of brightness. DLP is not suitable for everyone because some people will be sensitive to their rainbow effect which appears on the sequence of very bright scenes. DLP is a technology suitable for home cinema and video games if you are not sensitive to the rainbow effect and are not looking for strong light.

• LCD technology

LCD technology, or more exactly tri-LCD for projectors, is based on the same principle as on television sets. The LCD matrices let more or less pass the light of the lamp located behind. This technology allows a strong luminosity. It provides detailed and vivid images but is performing not so well on the depth of blacks. Motion blur can be more pronounced which can be penalizing for sports or video games. However, recent progress by specialized manufacturers has made it possible to offer tri-LCD projectors that are very suitable for home cinema.

• Laser technology

Still relatively expensive, this technology offers exceptional brightness. An asset when the room where you are projecting is too bright. The image is also very accurate from a colorimetric point of view.

• LCoS technology

Borrowing from DLP and LCD technologies because using matrices made up of liquid crystals and no longer mirrors, the LCoS offers the best image quality with, however, a slight motion blur. There are Full HD and Ultra HD devices from the mid-range to the most expensive equipment meeting the standards of projection rooms. JVC and Sony make their own chips. Rather than LcoS, they are respectively named D-ILA and SXRD. If your budget allows it, this will be the best choice to combine home theater and universal use without having to darken the room. Indeed, the image is precise, natural and contrasted, while being luminous with deep blacks.

3- Various selection criteria

• Light source

If the price of projectors has been falling steadily for years, be careful however with the price of the light source which wears out over time and whose replacement can cost from one hundred to several hundred euros. Depending on the model, this light source can be a UHP (Ultra High Pressure) bulb, a laser or even LEDs. Not all of these types of light sources provide the same brightness or the same lifespan.

The UHP lamp is the most commonly used type of light source. They can operate 10,000 hours or more, or 5 to 10 years of use. They have the advantage of being less expensive. However, as they heat up a lot, they require a large fan. The latter sometimes makes some models quite noisy.

Lasers and LEDs: with a duration of 20,000 to 30,000 hours, these two recent types of light source last 2 to 3 times longer than a UHP lamp but are worth twice as much. On a high-end model, the bill can therefore quickly rise to several hundred euros.

As they heat much less than a high pressure bulb, LEDs and lasers allow much quieter operation.

•Luminosity

Expressed in lumens, brightness determines the ability of the projector to deliver a vibrant image, even when the room is not in complete darkness.

Unfortunately, since manufacturers all have their own way of counting, it is complicated to give precise values, especially since, depending on the technology (LCD, LDP, etc.), these lumens are not counted in the same way. It is therefore important to be able to go to a store to see the device in operation. However, here are some approximate values. For home cinema use in the dark, 1000 lumens are sufficient. To watch contents in a partially-darkened room, better have 1500 lumens. To watch contents in broad daylight, you have to approach or exceed 2,000 lumens.

•Contrast

It is the ratio of the blackest black to the whitest white in an image. This ratio is expressed as a typical ratio of 800: 1, 2000: 1, etc. The higher it is, the more the image will be contrasted. As a minimum, you could be satisfied with 1000: 1, but for home cinema use, you should aim for 2000: 1 or more.

•Noise level

A heavily ventilated video projector (because it is equipped with a UHP lamp) will be noisier than if it is equipped with LEDs or a laser. However, manufacturers have made great progress and currently the noise standard in home cinema is below 40 dB. Depending on the location of the device during projection, or even the location of the fan on the device, noise level will not be the same. Also pay attention to the mode selection of the lamp. Most models offer a fairly quiet low mode and a much noisier high mode. This is not a problem in itself, because in home cinema the low mode is preferred, but the high mode can be used when necessary, for example to watch videos without darkening completely the room.

4- Conditions of use

• Room lighting

In terms of video projection, you have the choice between complete darkness or semi-darkness. Even with equipment offering exceptional brightness and contrast, a projection in broad daylight will never provide a fully satisfying experience.

  • Type of room

The ideal situation is to be able to mount the projector on the ceiling to project on a wall or a screen located opposite. In this case, all projectors will be suitable. But in most cases, it will be difficult to have a perfectly adjusted image, whether it's horizontally or vertically. In such a case, you should opt for a projector equipped with a lens shift which can be more or less important depending on the models and technologies. It corrects an axis shift for an always perfect image. Another important point, when the projector is higher or lower than the image, is the appearance of the trapezoid effect with sides of the image then converging up or down. In this case, it is necessary to check that the video projector is well equipped with this possibility of adjustment also called keystone. It should also be noted that the lens shift and focus settings can be done directly by knobs on the projector, or more conveniently via electric controls, using the remote control of the device.

• Image size and positioning distance

The positioning of a video projector is calculated by dividing the distance between the screen and the video projector by the width of the image. However, as the maximum image size depends on the type of device, its brightness and the recommended distance varies depending on the resolution (HD, Full HD or Ultra HD), it is therefore better to rely on a calculator, available on the Internet.

If you don't have enough distance, you can turn to a very short projector. With some models, you can place the device at the bottom of the screen. At the same time, this also could fix the problem of hanging from the ceiling and of having cables.

• Screen

It is an important part of the budget. When you have a smooth white wall, it is tempting to use it. It's more economical, but any coin has its reverse, there are advantages to preferring a screen.

When it is of high quality, it gives a better image, without absorbing or diffusing light. This feature is called the gain. For home cinema use, it should be checked that this gain indicated by the manufacturer is 1 or 1.1. When the room is a little bright, you can go up to 2.5.

The screen also provides a visual frame when bordered in black, which is preferable. It also makes it easier to adjust the image.

Regarding the material, you can opt for a mat PVC screen (gain from 1 to 1.2) which has the advantage of being solid and easy to clean. When the screen is particularly large, we may prefer fiberglass, which is thicker, which will guarantee perfect flatness.

For rooms that are too bright, you can turn to pearl canvases. These have a significant gain but are more fragile.

It should also be noted that there are special paints for walls and otherwise a good quality satin white should be preferred.

•Sound

For the experience to be complete, a home cinema installation must also provide good quality sound. If you do not want to embark on a complicated installation, you can choose to equip yourself with a sound bar, placed at the bottom of the screen. The current models, very powerful, are composed of several types of loudspeakers and are often wireless. You can also in some cases add a subwoofer or additional speakers. Another possibility is to turn to an all-in-one stereo system sold with a speaker package.

Finally, to obtain a top quality, you may equip yourself with an amplifier specially designed for 5.1 or 7.1 home cinema, therefore accompanied by a central speaker, two speakers at the front, two at the rear and a subwoofer (5.1 surround), and with two additional speakers on the sides (7.1 surround). Capable of decoding many audio formats (Dolby Digital, Dolby Atmos, DTS…), this type of material only makes sense with a high-end video projector.