Projector Calculation

[Carlito Austin]

A projector's distance from the lens to the screen surface is called the Throw Distance. The throw distance and the size of the imageit produces on the screen are proportional to each other based on the optics of the lens. As you increase the distance between theprojector lens and the screen the image will also increase.

A projector's distance from a screen andthe size of the image it produces are proportional to each other based on the optics of the lens. As you increase the distance between the projectorand a screen the image will also increase. If your projector has a zoom lens, the lens can be adjusted to change the size of the screen image without changingthe distance of the projector. Since each projector lens is different, an online projection calculator tool will help you calculate the size of an imageon a screen relative to how far the projector is placed from screen.

For any given projector, the width of the image (W) relative to the throw distance (D) is know as the throw ratio D/W or distance over width. Sofor example, the most common projector throw ratio is 2.0. This means that for each foot of image width, the projector needs to be 2 feet away orD/W = 2/1 = 2.0. So if I'm using a projector with a throw ratio of 2.0 and I have an image width of 5 feet, then my throw distance must be10 feet. So the throw ratio is a simple formula that let's you easily compute throw distance or image width given that you know one of thesemeasurements. A projector zoom lens will have two different throw ratios, one for the minimum zoom setting and one for the maximum zoom setting.

A short throw projector is a projector with a lens that has a throw ratio of 0.4 (distance/width) or less. These projectors are ideal for rear screen applicationswhere the area behind the screen is limited, or for a wall mounted application where the projector will be mounted within 1 or 2 feet from the screen. Thegoal of these projectors is to produce as large of an image within the shortest amount of space between the projector and the screen.

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We develop a technique based on density functional theory and the projector augmented wave method in order to obtain the x-ray absorption cross section at a general edge, both in the electric dipole and quadrupole approximations. The method is a generalization of Taillefumier et al., [Phys. Rev. B 66, 195107 (2002)]. We apply the method to the calculation of the Cu L2,3 edges in fcc copper and cuprite (Cu2O), and to the S L2,3 edges in molybdenite (2H-MoS2). The role of core-hole effects, modeled in a supercell approach, as well as the decomposition of the spectrum into different angular momentum channels are studied in detail. In copper we find that the best agreement with experimental data is obtained when core-hole effects are neglected. On the contrary, core-hole effects need to be included both in Cu2O and 2H-MoS2. Finally we show that a non-negligible component of S L2,3 edges in 2H-MoS2 involves transition to states with s character at all energy scales. The inclusion of this angular momentum channel is mandatory to correctly describe the angular dependence of the measured spectra. We believe that transitions to s character states are quantitatively significant at the L2,3 edges of third row elements from Al to Ar.

Oana Bunău*

• Institut de Minralogie et de Physique des Milieux Condenss, Universit Paris 6, Centre National de la Recherche Scientifique, 4 Place Jussieu, F-75252 Paris, France and Instituto de Ciencia de Materiales de Aragn and Departamento de Fisica de la Materia Condensada; Universidad de Zaragoza - Consejo Superior de Investigaciones Cientficas, E-50009 Zaragoza, Spain

Please note that the calculated values may differ slightly from the real values due to mathematical rounding (+/- 5%).
The calculation is performed for each interchangeable lens appropriate to the selected Sharp/NEC projector.

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The relationship between projection distance and screen size is defined as Throw Ratio = Throw Distance / Image Width, which can calculate a distance 8.2ft from the wall for projection of a 100-inch image with a 16:9 aspect ratio (image width is approximately 7.2ft).

Look for information about screen size and distance, typically expressed as "screen size @ distance" from the screen. In this example, the specification "100"@ 8.2ft " means that the minimum distance you will need is 8.2ft from the projector to the wall to get a 100-inch screen size, which is an ideal projector set up in a space of about 21 sq. ft to 32 sq. ft.

The projection is determined by your room size, where the projector will be placed, and the distance from the projector to the projection screen/wall. To select the ideal projector for your home, you will need to measure the length and width of the room to use the maximum distance the projector can be placed from the screen to search for the specific projector model that will meet your ideal screen size needs. If the space has an irregular shape, such as an L shape or a polygon, measure the distance between the two walls as the reference for purchasing a projector. Keep in mind the best setup position is where two walls are furthest apart in the space.

There are many choices in terms of device size and projector lens design. Among all existing projectors, a throw ratio around 1.13:1 is the most common design that has the lens in the front of the projector. These designs can require distances as short as 8.2ft to project a 100-inch screen, which is the most common throw distance setup in limited space or small apartments.

Some projectors with the short-throw lens can save more space from the projector to the wall, offering a shorter projection distance for the same 100-inche screen (100"@6.6ft). There are also models with the lens placed inside the projector body to project images upward onto a screen above and behind the projector body. These ultra-short throw models only require a distance of less than 3.3ft to project a 100-inch screen. These options make it easy to enjoy large screens, even if the room is smaller than 6.5ft2.

If the projector can be mounted on the ceiling or placed on a table aligned to the center of the screen, only the "screen size @ distance" information is needed when selecting a projector. But if the projector cannot be aligned to the center of the screen leading to screen distortion, the projector must be equipped with keystone correction or lens shift design. Some projectors offer vertical keystone correction, while others include both vertical and horizontal keystone correction. If the projector can be aligned to the center of the screen but must be tilted at an angle to fill the screen, then only vertical keystone correction is needed to project images fully and accurately. But if the projector cannot be aligned to the center of the screen due to room dcor and must be placed by a wall or a corner, a model with both vertical and horizontal keystone correction is needed.

As a movie event producer be it your backyard or a professional event, you always deal with different projector models.

Whether you are considering to upgrade your projector for the next outdoor movie party or your client asks if they can use a projector from their presentation room -- in all these scenarios a projection calculator comes in handy.

There is also a feature to lock screen size value or projection distance value. The use scenario described above includes the locked screen size value. The variable projection distance value is useful when:

Our easy-to-use interactive simulation tool helps AV installers and specifiers calculate throw distance and image size for Sony professional projectors for installation. See instantly how projected image size and position vary, depending on parameters including choice of lens, screen size, aspect ratio, shift range, and floor or ceiling installation. Free download for Microsoft Windows (Version 23) or iOS.

Calculator accuracy +/-5%. The calculator is designed to help you plan your installation and find the right projector. It is not designed to provide exact dimensions.When calculating the throw distance, bear in mind that the distance is measured from the front of the lens to the projection surface, except for Ultra Short Throw projectors with a mirror system. Where possible, attempt to position the projector in the middle of the zoom range , which is where the optics is optimized for. Try to avoid the extreme outer boundaries as the projector lenses has variance and performance tolerances that could make the screen not being filled, or the image being larger than the screen, caused by small variances in the optical systems. If you need to be at the extreme outer boundaries, we recommend that you order the projector and test the actual distance in your environment before fixing any mounting parts to the wall or ceiling.

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