February 8, 2018 at 16:04Choosing a Home Theater Projector
From a projector in a home theater, first of all, a high-quality picture is required. We will describe in this material about how it is formed, what components affect what, and how to choose the best option based on this information.
Speaking of a multimedia projector, we mean a device that can reproduce an image by receiving a digital signal. Sometimes the projector may itself play some types of files, however, a detailed analysis of this functionality is beyond the scope of our review. In addition, since analog devices are almost out of the market, here we will focus only on digital projectors.
The projector forms an image using, relatively speaking, 4 components:
Each component contributes to the final result. To make an informed choice, you need to imagine which component is responsible for what.
The source can be a halogen or other gas discharge lamp, as well as LEDs or lasers of three primary colors.
The source should give a large and uniform light flux so that the picture is bright, and at the same time have a reasonable life. Halogen lamps give a fairly bright luminous flux, but their service life is small. In addition, such a lamp heats up, which leads to the rapid failure of neighboring components - in the first place, the matrix. And for some types of discharge lamps, degradation of power during operation is characteristic.
Lamps are used in most home theater models of any price range, such as the Acer V9800 or Canon LV-X320 .
Acer v9800
Canon LV-X320
There are many variations of halogen and discharge lamps, but their relatively short service life combines. In relation to home theaters, the service life must be taken into account in conjunction with the service of the manufacturer itself. In this segment there are quite expensive models, and some manufacturers, such as Canon, are ready to provide replacement lamps during the warranty period under certain conditions - at least registering the device on the site.
LEDs and lasers allow you to not use filters in the modulator and last longer than lamps. But LEDs often do not provide enough light, and lasers are expensive and difficult to set up for more or less natural color reproduction, so they are used much less often in home theater devices. For example, they have a family of LG models, in particular, the LG PF1500G. More often LEDs and lasers are found in universal projectors or in expensive installation models.
There are solutions where LEDs and lasers complement each other, but their main drawback is the relatively high price.
Three technologically different types of modulators are common on the market:
As with light sources, each of the existing technologies has its own advantages and disadvantages. For example, DLP provides higher image contrast than the closest competitor - LCD. On the other hand, when changing images quickly, DLP has image artifacts. LCoS combines the advantages of both LCD and DLP, although at the same time it has a high price.
To obtain a color image, the projector uses one or more modulators. If there is only one modulator, it is illuminated by a luminous flux, which in turn passes through different filters. To do this, a rotating disk is installed in the path of the light flux, the sectors of which are filters of different colors. Thus, red, green and blue images are alternately created, which due to inertia of vision are mixed for the viewer into one color. Sometimes transparent is added to the three main filters, which helps to increase contrast, however, to the detriment of saturation.
The device in this case comes out more expensive, but on the moving images there is no noticeable flicker and the so-called rainbow effect. In addition, the picture on such projectors will be brighter (at the same light source power). Designs with three modulators can use not one, but three sources of different colors (instead of a system of mirrors, prisms and filters), which allows to further increase the brightness of the image.
Obviously, projectors with three modulators, all other things being equal, are more expensive and massive. At the same time, higher requirements are imposed on them for accuracy of assembly, since the light fluxes passing in different ways should form a clear picture.
The technologies described above are quite difficult to line up in terms of formal characteristics, since the subjective impression of the picture is determined by other components of the projector. Manufacturers either choose the more advanced technology of the light source and modulator, or invest in related technical solutions to compensate for many of the shortcomings of simple approaches in a particular use case. So in comparison, it is always necessary to take into account specific models and assigned tasks.
In the home theater projection segment, most often either one DLP matrix or three LCD matrices is used. At the same time, the price of the projector is practically independent of technology.
Examples of using a single DLP matrix: NEC NP-V332XG or Panasonic PT-AE8000EA .
NEC NP-V332XG
Another option is three LCD matrices: Epson EH-TW550 or Panasonic PT-LB332E .
Epson EH-TW550
Panasonic PT-LB332E
For comparison, an example using Sony's patented SXRD technology is the Sony VPL-HW45 .
The light modulator is the same element that determines the resolution of the image on the screen. The most popular now is FullHD (1920x1080). There are extremely expensive projectors with support for 4K; 4K comes to this segment with some delay regarding the TV market. At the same time, even among the various "TOP-10" of this year, there are a lot of devices even without FullHD support. More often they belong to the lower price range. A good example is the Canon LV-X320 .
FullHD permissions in most cases are enough for a living room. The picture below explains in which cases you should not overpay for pixels:
Recommended screen size depending on viewing distance.
Vertical - viewing distance, horizontal - screen size. The plane is divided into sectors corresponding to different image resolutions. The boundaries of these zones represent the distance at which, for a given diagonal of the screen, the subjective difference between the higher and lower resolution pictures disappears.
When studying this picture, we recommend that you rely on ideas about the viewing angles of the screen. TVs are usually recommended to be set so that the viewing angle is about 35 degrees (this means that the distance to the screen is about 3 times its diagonal). For comparison: in the IMAX cinema, the viewing angle is 60-120 degrees horizontally and 40-80 degrees vertically (depending on the location in the hall).
After talking about pixels and angles, we move on to another component of the projector - optics. Its task is to provide the maximum viewing angle without image distortion. In the most understandable interpretation - a larger viewing angle allows you to get a larger diagonal of the image with less distance to the projector. However, it is worth remembering that a larger image size means a larger pixel size, which brings us back to the discussion of resolution.
Like photo lenses, the optics of projectors differ in focal length, which determines the ratio of the projection (how large the image can be obtained from this distance or how far the projector needs to be placed to get an image of a given diagonal). The larger the focus, the less likely it is to get picture distortion. On the other hand, the smaller the focus, the closer to the screen you can position the projector (and in the rooms the installation distance of the projector is in any case limited by walls).
As parameters characterizing optics, the minimum / maximum distance to the screen with the minimum / maximum diagonal is often indicated (if only one group of values is indicated, then the ratio of the viewing distance to the image diagonal is usually added to them). For example, on Yandex.Market, the BenQ W1050 model description includes the following data:
By analogy with cameras, the projectors' optics can be interchangeable, but more often these models belong to the segment of installation devices.
The task of electronics is to control all of the above components to obtain a clear image on the screen in manual or automatic mode (depending on the declared functions of the device). In particular, electronics compensates for optical distortion of the picture. Some devices even have special tools for automatic distortion compensation (for example, Epson's Screen Fit ).
We talked a lot about the imperfection of the technologies used in modern projectors for image formation (and in fact there are much more). Electronics can partially compensate for them. Using iris control, you can get a more pronounced black color for LCD projectors or reduce the rainbow effect for DLP - like in AcuMotionfrom Acer, which generates intermediate frames on fast-paced scenes to create smoother motion. Also, electronics help optimally consume lamp life - such as in the BenQ projectors LampSave technology , which dynamically controls brightness for longer life.
Electronics is also responsible for the formation of 3D. The vast majority of home projectors use technology active glasses synchronized with the projector. The technology of image formation for different eyes using different parts of the spectrum has already been proposed, which allows not to use a special screen. But the lack of a large amount of 3D content, the very need to wear glasses and subjective decrease in the brightness of 3D images (due to losses when filtering glasses) are against the spread of this technology. Despite this, there are quite a lot of 3D models on the market.
Above, we conditionally divided the projector into components. The technologies used in them not only offer advantages, but also create limitations, the struggle against which gives rise to various engineering difficulties - the need for noisy cooling, dust, stray light reflections, etc. As a result, the development of projectors rests not only in the search for new ideas, but also in the constant struggle against shortcomings.
And the components can influence each other: you can’t just connect together an arbitrary light source, some kind of image formation technology and one way to create colors. In this case, the shortcomings of each of the approaches can reinforce each other and the device will turn out not competitive. So, speaking of minimizing problems, we mean working on the entire device as a whole.
It is reasonable to include a screen in the list of elements that determine the subjective quality of the output image. The geometry and coverage of the screen, as well as the illumination of the room where it is installed, inevitably affect the perception of the picture.
For example, the farther the screen is from the projector, the larger the image itself at the same viewing angle. But it is perceived less bright (luminous flux per unit area decreases). And the brighter the ambient lighting, the brighter you need a projector for the same tasks.
The screen is usually purchased separately and can be matched to specific requirements. Typically, geometry, installation method (wall or ceiling fixtures are relevant for a home; a tripod or floor installation is less convenient in everyday life), the presence of an automatic drive that minimizes the screen, and also the coating. The last factor is perhaps the most important, since it allows you not to lose the brightness and contrast of the image due to incomplete reflection. However, the characteristics of coatings are a topic for another discussion.
Before making the final choice, you need to decide on the budget and answer questions about the proposed use case.
If the projector will act as a universal replacement for the TV (working in the background, playing games, watching a movie), we need a “long-playing harvester”. Here you can not pay much attention to the subtleties of color reproduction and contrast, since in such conditions they simply will not appear. As a result, the choice is likely to fall on the 3LCD model.
If we need a full-fledged home theater (off lights, picture quality requirements), i.e. we focus on the beauty of color (accurate color reproduction, real black) to the detriment of brightness - we look towards DLP.
After that, the parameters of the room and the available places for mounting the projector are used - this information will give us the required optics parameters (or the desired distance to the screen / diagonal).
Speaking of a multimedia projector, we mean a device that can reproduce an image by receiving a digital signal. Sometimes the projector may itself play some types of files, however, a detailed analysis of this functionality is beyond the scope of our review. In addition, since analog devices are almost out of the market, here we will focus only on digital projectors.
The projector forms an image using, relatively speaking, 4 components:
- light source;
- “Modulator”, thanks to which we see not just the light of the lamp, but a color picture;
- optics that allow you to focus the image on the screen;
- the electronics that drives it all.
Each component contributes to the final result. To make an informed choice, you need to imagine which component is responsible for what.
Light source
The source can be a halogen or other gas discharge lamp, as well as LEDs or lasers of three primary colors.
The source should give a large and uniform light flux so that the picture is bright, and at the same time have a reasonable life. Halogen lamps give a fairly bright luminous flux, but their service life is small. In addition, such a lamp heats up, which leads to the rapid failure of neighboring components - in the first place, the matrix. And for some types of discharge lamps, degradation of power during operation is characteristic.
Lamps are used in most home theater models of any price range, such as the Acer V9800 or Canon LV-X320 .
There are many variations of halogen and discharge lamps, but their relatively short service life combines. In relation to home theaters, the service life must be taken into account in conjunction with the service of the manufacturer itself. In this segment there are quite expensive models, and some manufacturers, such as Canon, are ready to provide replacement lamps during the warranty period under certain conditions - at least registering the device on the site.
LEDs and lasers allow you to not use filters in the modulator and last longer than lamps. But LEDs often do not provide enough light, and lasers are expensive and difficult to set up for more or less natural color reproduction, so they are used much less often in home theater devices. For example, they have a family of LG models, in particular, the LG PF1500G. More often LEDs and lasers are found in universal projectors or in expensive installation models.
There are solutions where LEDs and lasers complement each other, but their main drawback is the relatively high price.
Light modulator
Three technologically different types of modulators are common on the market:
- Translucent Liquid Crystal Matrix (LCD) - one or more in the device;
- an array of microscopic controlled mirrors on a chip that can be fixed in one of two positions (DLP - Digital Light Processing) - also one or more;
- LCOS reflective LCD matrix (Sony version - SXRD; three-chip version from JVC - D-ILA), more resistant to high-power light emission;
As with light sources, each of the existing technologies has its own advantages and disadvantages. For example, DLP provides higher image contrast than the closest competitor - LCD. On the other hand, when changing images quickly, DLP has image artifacts. LCoS combines the advantages of both LCD and DLP, although at the same time it has a high price.
To obtain a color image, the projector uses one or more modulators. If there is only one modulator, it is illuminated by a luminous flux, which in turn passes through different filters. To do this, a rotating disk is installed in the path of the light flux, the sectors of which are filters of different colors. Thus, red, green and blue images are alternately created, which due to inertia of vision are mixed for the viewer into one color. Sometimes transparent is added to the three main filters, which helps to increase contrast, however, to the detriment of saturation.
The device in this case comes out more expensive, but on the moving images there is no noticeable flicker and the so-called rainbow effect. In addition, the picture on such projectors will be brighter (at the same light source power). Designs with three modulators can use not one, but three sources of different colors (instead of a system of mirrors, prisms and filters), which allows to further increase the brightness of the image.
Obviously, projectors with three modulators, all other things being equal, are more expensive and massive. At the same time, higher requirements are imposed on them for accuracy of assembly, since the light fluxes passing in different ways should form a clear picture.
The technologies described above are quite difficult to line up in terms of formal characteristics, since the subjective impression of the picture is determined by other components of the projector. Manufacturers either choose the more advanced technology of the light source and modulator, or invest in related technical solutions to compensate for many of the shortcomings of simple approaches in a particular use case. So in comparison, it is always necessary to take into account specific models and assigned tasks.
In the home theater projection segment, most often either one DLP matrix or three LCD matrices is used. At the same time, the price of the projector is practically independent of technology.
Examples of using a single DLP matrix: NEC NP-V332XG or Panasonic PT-AE8000EA .
Another option is three LCD matrices: Epson EH-TW550 or Panasonic PT-LB332E .
For comparison, an example using Sony's patented SXRD technology is the Sony VPL-HW45 .
The light modulator is the same element that determines the resolution of the image on the screen. The most popular now is FullHD (1920x1080). There are extremely expensive projectors with support for 4K; 4K comes to this segment with some delay regarding the TV market. At the same time, even among the various "TOP-10" of this year, there are a lot of devices even without FullHD support. More often they belong to the lower price range. A good example is the Canon LV-X320 .
FullHD permissions in most cases are enough for a living room. The picture below explains in which cases you should not overpay for pixels:
Recommended screen size depending on viewing distance.
Vertical - viewing distance, horizontal - screen size. The plane is divided into sectors corresponding to different image resolutions. The boundaries of these zones represent the distance at which, for a given diagonal of the screen, the subjective difference between the higher and lower resolution pictures disappears.
When studying this picture, we recommend that you rely on ideas about the viewing angles of the screen. TVs are usually recommended to be set so that the viewing angle is about 35 degrees (this means that the distance to the screen is about 3 times its diagonal). For comparison: in the IMAX cinema, the viewing angle is 60-120 degrees horizontally and 40-80 degrees vertically (depending on the location in the hall).
Optics
After talking about pixels and angles, we move on to another component of the projector - optics. Its task is to provide the maximum viewing angle without image distortion. In the most understandable interpretation - a larger viewing angle allows you to get a larger diagonal of the image with less distance to the projector. However, it is worth remembering that a larger image size means a larger pixel size, which brings us back to the discussion of resolution.
Like photo lenses, the optics of projectors differ in focal length, which determines the ratio of the projection (how large the image can be obtained from this distance or how far the projector needs to be placed to get an image of a given diagonal). The larger the focus, the less likely it is to get picture distortion. On the other hand, the smaller the focus, the closer to the screen you can position the projector (and in the rooms the installation distance of the projector is in any case limited by walls).
As parameters characterizing optics, the minimum / maximum distance to the screen with the minimum / maximum diagonal is often indicated (if only one group of values is indicated, then the ratio of the viewing distance to the image diagonal is usually added to them). For example, on Yandex.Market, the BenQ W1050 model description includes the following data:
By analogy with cameras, the projectors' optics can be interchangeable, but more often these models belong to the segment of installation devices.
Electronics
The task of electronics is to control all of the above components to obtain a clear image on the screen in manual or automatic mode (depending on the declared functions of the device). In particular, electronics compensates for optical distortion of the picture. Some devices even have special tools for automatic distortion compensation (for example, Epson's Screen Fit ).
We talked a lot about the imperfection of the technologies used in modern projectors for image formation (and in fact there are much more). Electronics can partially compensate for them. Using iris control, you can get a more pronounced black color for LCD projectors or reduce the rainbow effect for DLP - like in AcuMotionfrom Acer, which generates intermediate frames on fast-paced scenes to create smoother motion. Also, electronics help optimally consume lamp life - such as in the BenQ projectors LampSave technology , which dynamically controls brightness for longer life.
Electronics is also responsible for the formation of 3D. The vast majority of home projectors use technology active glasses synchronized with the projector. The technology of image formation for different eyes using different parts of the spectrum has already been proposed, which allows not to use a special screen. But the lack of a large amount of 3D content, the very need to wear glasses and subjective decrease in the brightness of 3D images (due to losses when filtering glasses) are against the spread of this technology. Despite this, there are quite a lot of 3D models on the market.
Above, we conditionally divided the projector into components. The technologies used in them not only offer advantages, but also create limitations, the struggle against which gives rise to various engineering difficulties - the need for noisy cooling, dust, stray light reflections, etc. As a result, the development of projectors rests not only in the search for new ideas, but also in the constant struggle against shortcomings.
And the components can influence each other: you can’t just connect together an arbitrary light source, some kind of image formation technology and one way to create colors. In this case, the shortcomings of each of the approaches can reinforce each other and the device will turn out not competitive. So, speaking of minimizing problems, we mean working on the entire device as a whole.
Screen and light
It is reasonable to include a screen in the list of elements that determine the subjective quality of the output image. The geometry and coverage of the screen, as well as the illumination of the room where it is installed, inevitably affect the perception of the picture.
For example, the farther the screen is from the projector, the larger the image itself at the same viewing angle. But it is perceived less bright (luminous flux per unit area decreases). And the brighter the ambient lighting, the brighter you need a projector for the same tasks.
The screen is usually purchased separately and can be matched to specific requirements. Typically, geometry, installation method (wall or ceiling fixtures are relevant for a home; a tripod or floor installation is less convenient in everyday life), the presence of an automatic drive that minimizes the screen, and also the coating. The last factor is perhaps the most important, since it allows you not to lose the brightness and contrast of the image due to incomplete reflection. However, the characteristics of coatings are a topic for another discussion.
What to choose: ask the right questions
Before making the final choice, you need to decide on the budget and answer questions about the proposed use case.
If the projector will act as a universal replacement for the TV (working in the background, playing games, watching a movie), we need a “long-playing harvester”. Here you can not pay much attention to the subtleties of color reproduction and contrast, since in such conditions they simply will not appear. As a result, the choice is likely to fall on the 3LCD model.
If we need a full-fledged home theater (off lights, picture quality requirements), i.e. we focus on the beauty of color (accurate color reproduction, real black) to the detriment of brightness - we look towards DLP.
After that, the parameters of the room and the available places for mounting the projector are used - this information will give us the required optics parameters (or the desired distance to the screen / diagonal).