Service life
Minimum projector lamp life as stated by the manufacturer. Specified by the total time of continuous operation. Note that if the projector was operated without violations, then upon reaching this time, the lamp will not necessarily fail — on the contrary, it can work for quite a long time. However, when evaluating durability, it is best to focus on the claimed service life.
Brightness
The brightness of the image produced by the projector at maximum backlight brightness. Usually, the average brightness of the screen, derived from a special formula, is indicated. The higher it is, the less the image depends on ambient light: a bright projector can provide a clearly visible image even in daylight, but a dim one will require dimming. On the other hand, increasing brightness reduces contrast and accuracy of colour reproduction.
Accordingly, when choosing this parameter, you need to consider the conditions in which you plan to use the projector. So, for office or school/university use, a brightness of at least 3000 lm is desirable — this allows you to get normal visibility without obscuring the room. In turn, among the top models a very low brightness can be found, because. such projectors are usually installed in rooms specially designed for them with good darkness level. And in ultra-compact devices it is impossible to achieve high brightness for technical reasons.
Detailed recommendations on the optimal brightness for certain conditions can be found in special sources. Here we note that anyway, it is worth choosing according to this indicator with some margin. As mentioned above, as brightness increases, contrast and colour quality decrease, and you may need to use the projector at a reduced brightness to achieve the desired picture quality.
Real resolution
The native resolution of the image produced by the projector matrix.
The minimum for modern projectors is actually
the VGA standard, which assumes a resolution of 800x600 or close to it. The most limited of modern high-definition standards is
HD (720); the classic size of such a frame is 1280x720, but projectors also have other options (up to 1920x720). A more advanced HD format is
Full HD (1080), which also has several variations (the most popular is 1920x1080). And among high-end projectors there are models of
Quad HD,
Ultra HD (4K) and even
Ultra HD (8K) standards.
In general, the higher the resolution, the clearer and more detailed image the projector can produce. On the other hand, this indicator directly affects the cost, and all the benefits of high resolution can only be appreciated if the reproduced content also corresponds to it. Note that modern projectors can work with higher resolutions than the “native” ones – for more details, see “Maximum video resolution”.
Rear projection
The ability of the projector to operate in the
rear projection mode (“mirroring” the image).
There are two main types of rear projection. Most often, horizontal mirroring is found in projectors — it is used when installing the device behind a translucent screen. Vertical inversion, in turn, is used in projectors with fixed keystone correction — due to their design, when mounted under the ceiling, such devices must be turned upside down, which requires the corresponding correction of the displayed image.
Throw distance, min
The closest distance to the screen that the projector can be used on. Typically, this is the minimum distance at which the image from the projector remains in focus.
This parameter is especially important if the device is to be placed at a small distance from the screen (for example, in a cramped room). Some modern projectors are able to work normally at a distance of 10 – 20 cm. Also note that the throw distances are determined primarily by the lens, and if the initial range of these distances does not suit you, perhaps the situation can be solved by replacing the optics.
Throw distance, max
The farthest distance from the screen that the projector can be used on. This is the maximum distance at which the image remains in focus and maintains acceptable brightness — at least enough for viewing in a darkened room on a high-quality screen.
It is necessary to choose according to this parameter taking into account the expected operating conditions and the distances to be dealt with. At the same time, it's ok to have a certain margin for the maximum distance — since, as already mentioned, it is usually indicated for an perfect screen and a darkened room, and such conditions are not always available. Also note that although the throw distances depend on the lens, not every projector with an interchangeable lens allows the installation of more "long-range" optics than the standard one — the device may simply not have enough brightness for an increased distance.
Image size
Diagonal size of the image projected by the projector. Usually, it is indicated as a range — from the smallest, at the minimum throw distance, to the largest, at the maximum. About throw distances, see above; here it is worth saying that the choice of diagonal size depends both on the distance between the screen and the audience, and on the format of the projector. For example, to watch a video, the best option is the situation when the distance from the viewer to the image corresponds to 3-4 diagonals, and a relatively large picture can be useful for working with presentations. More detailed recommendations for different situations can be found in special sources; here we only recall that the image must fit on the screen used with the projector.
Digital zoom
The magnification range of digital zoom provided by the projector.
It is impossible to increase the diagonal digitally, so in this case we are usually talking about enlarging the image within the existing diagonal. Thus, for example, you can “stretch” a photo or diagram to fill the screen, removing the frames around the edges, enlarge a separate fragment of the image for a more detailed examination, etc. And in some models, digital zoom means, in fact, a reduction, when instead of the entire sensor only part of it is used. This can be useful if the original size of the image does not fit the screen.
It is worth noting that in both cases, the operation of the “zoom” is associated with a decrease in resolution and some deterioration in the overall quality of the picture.
Keystone correction (vert), ±
Vertical keystone correction allows you to align the image when the projection ray is shifted from the centre of the screen in a vertical plane. If the projector is suspended from the ceiling and shines from top to bottom, a vertical keystone occurs. And the function of vertical keystone correction allows you to align the picture.
In most cases, projectors can only correct vertical keystone. But the keystone can also be horizontal if the projection ray is offset from the centre of the screen in the horizontal plane. Advanced models are often equipped with an auto keystone correction feature (see the relevant paragraph). In this case, the keystone is aligned in a fully automatic mode, without user participation.
