Installing a television is a fairly simple task, but you have to plan a few things for installing projector. We explain which specifications you should pay attention to, and how they affect the setup. This way you have all the necessary knowledge to choose the ideal projector for your room.
installing projector: Viewing distance and screen size
You don’t buy a projector to shine a 40 ″ image on the wall. To really enjoy the best projector experience, we recommend aiming for at least 80 ″ screen diagonal, and preferably even 100 to 110 inches. Incidentally, the 110-inch diagonal image is 2.44 m wide and 1.37 m high (16: 9 aspect ratio).
But how far are you from such a giant image? In any case, closer than to a television, after all we aim for a real cinema experience. For projectors, we recommend a field of view of about 37 degrees for that movie experience. That means that you place the chair at a distance of 1.3 times the screen diagonal. For sports, news and some more relaxation programs, you can make the image a bit smaller, so that you are, for example, at 1.6 times the screen diagonal. For that 110-inch image, that translates into a viewing distance of 3.6 to 4.5 meters.
installing projector: Projection ratio
The size of the projected image depends on the distance between the front of the projector lens and the screen. We call this property of the lens the projection ratio (in English: throw ratio). The projection ratio is the ratio of the distance between lens and screen and the width of the image, in the figure it is (A / B).
For example, a projection ratio of 1.5 means that you achieve a screen width of 2 meters from 3 meters away. A high throw ratio means that the projector must be far back to give a large image, while a small throw ratio indicates that the projector will deliver a large image even when close to the screen. For example, a projection ratio of 0.5 means that you already have a 2 meter wide image if the projector is only 1 meter from the wall. We therefore call such projectors Short Throw projectors, or in extreme cases Ultra Short Throw.
installing projector: Zoom
Almost all projectors have a zoom lens, although the range of the zoom can vary widely (from 1.1 times to 2.1 times). The zoom lens makes the image larger or smaller, while you keep the projector at the same distance. Or vice versa, you keep the same image by sliding the projector forward or back and adjusting the zoom at the same time.
Projectors with a zoom lens have a throw ratio expressed as a range. The greater the zoom factor, the wider the range. For example, a throw ratio of 1.35-2.84 indicates a zoom lens of 2.1 times. If you want an image that is two meters wide, the projector should be somewhere between 2.7 and 5.68 meters from the screen.
installing projector: Lens offset
A projector is always in the center of the image, horizontally. But that is not the case vertically. The lens offset determines how high the top of the image is above the lens. Lens offset is a particularly tricky specification because not every manufacturer identifies them in the same way. A commonly used way is as follows: lens offset = distance from the top of the screen to the lens divided by the screen height (in the figure: H ‘/ H)
Typical examples: A lens offset of fifty percent means that the lens is level with the center of the image. A lens offset of one hundred percent means that the lens is level with the bottom of the image. You can also go higher. One hundred and ten percent means that the bottom of the image is ten percent of the image height above the lens.
In many cases, it is best to consult the manual. It always contains a clear diagram and / or table from which you can derive the lens offset.
Lens shift and Keystone correction
Is your projector not horizontally in the middle of the image and / or is it too high or too low for the lens offset? The best solution is to use lens shift to correct that. Lens shift allows you to shift the image horizontally or vertically, without distorting it. How much you can shift the image is always expressed as a percentage of the image height (vertical) or image width (horizontal).
or example, a lens shift of about fifty percent horizontal and about one hundred percent vertical means that from the neutral position you can shift the image up to fifty percent of the width to the left or right, and up to a hundred percent of the height up or down. Please note, in many cases you cannot use the maximums of lens shift together. For example, those who need all horizontal lens shift will see their vertical lens shift strongly limited and vice-versa. The manufacturer’s manual usually provides the best information in this case too.
Unfortunately, not every projector has lens shift. The only solution that remains in that case is to turn the projector slightly until the image is neatly on the screen. But that does introduce trapezoidal distortion in the image. You can get rid of it with the help of keystone correction. If you need to turn the projector left or right, you’ll need horizontal keystone correction to compensate. If you have to turn the projector up or down, you need vertical keystone correction.
Try to avoid keystoning as much as possible. After all, the digital operations that are performed on the image cause loss of detail.
A projector lamp must be thoroughly cooled, and fan noise is therefore almost inevitable with projectors. With DLP projectors, there is also the noise of the rapidly spinning color wheel. Depending on the room and setup, this can be a factor that you have to take into account, for example if you are sitting close to or under the projector.
How loud the projector is can generally be found in the specifications, it is expressed in dB (A). We can call projectors that remain below 20 dB (A) as whisper quiet. You will hardly hear them. If it is above 30 dB (A), you should without a doubt take it into account. All values in between depend on how annoying the noise is, and of course on how much you think it is.
Keep in mind that smaller projectors are generally louder. Specifications usually give two numbers, one for the lamp in normal mode, and one when the lamp is in eco mode. If only one value is stated, then for safety’s sake it is best to assume that this is for the eco mode, unless stated otherwise.
How do you choose a projector?
With all this information you can now choose the right projector. In general, you follow the following plan:
- Determine the desired screen size and viewing distance based on the room.
- Locate the projector and measure the distance from projector to screen (A).
- Divide the distance (A) by the width of your screen. The result is the desired projector ratio. It must be within range of the projector you choose.
- Determine the vertical distance between the lens and the top of the image (H).
- Divide that distance by the height of the image. The result is the desired lens offset.
- If this does not match the lens offset of the projector, then you need lens shift.
- If you have no or not enough lens shift, you have to tilt the projector and you need keystone correction. However, first try to see if you can not move the projector.