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Projection Lenses Questions and Answers with formulae

Source:Navitar Presentation Products

Frequently Asked Questions

Q. How do I calculate what size lens I require?

If you need to calculate the correct lens size you require, please use thefollowing formula for a very close approximation. If you have any

questions, please call and speak to one of our engineers.

Lens Focal Length = Projection Distance x LCD Panel Size (diag. or width)Screen Size (diagonal or width)

First, you must know the following information:

1. Screen size in inches (diagonal or width).2. Projector LCD panel size in inches (diagonal or width).

3. Projection distance in inches (measured from the front of the videoprojector housing to the screen).

It is very important that you be consistent. If you use the diagonal screensize measurement, then you must also use the diagonal measurement forthe projector LCD panel size. If using screen width, then use the LCDpanel size width. If you are working in inches, then you need to do all of

your calculations in inches. You can convert the lens size to millimeters atthe end. Please note the following information:

Screen Diagonal x 0.8 = Screen Width

LCD Diagonal x 0.8 = LCD Width

1 Foot = 12 Inches1 Inch = 25.4 Millimeters

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Example: You have an 80 projection distance from the screen to thefront of the LCD projector housing. The screen is 10 wide & the LCD hasa 1.3" diagonal.

Lens Focal Length = Projection Distance x LCD Size (diagonal or width)Screen Size (diagonal or width)

Lens Focal Length (Calculated in Inches)

= (80 x 12") x (1.3" x 0.8)= 960" x 1.04" = 8.32"

10 x 12" 120"

Lens Focal Length (Calculated in Millimeters)

= (80 x 12" x 25.4) x (1.3" x 0.8 x 25.4mm)(10 x 12" x 25.4mm)

= 24,384mm x 26.416mm = 644,127.74mm =211mm3,048mm 3,048mm

For this application, we recommend the 6-9" zoom lens, model

819MCZ900.

Q. If my image is 10 feet wide, how high will it be?

An easy way to determine image height is to take the image width anddivide it by its aspect ratio. The aspect ratio for standard video is

1.33:1.

Image Height = Image Width = 10= 7.5 (76" or 2,286mm)Aspect Ratio 1.33

The aspect ratio for HDTV and most "letterbox" formats is 1.77:1;therefore a 10 foot wide HDTV image will be 58" high.

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Q. How do I convert a diagonal measurement into width?

Just as most TV sizes are given in diagonals, the same is true of LCD

panel sizes. This is why we multiply the LCD panel size (a diagonalmeasurement) by 0.8 (4x3 standard format) or 0.87 (16x9 wide screenformat) to determine the "Aperture," which is the "Width" measurement.

Standard Format (4x3: 1)Width (or Aperture) = Diagonal Measurement x 0.8

Wide Screen Format (16x9: 1)

Width (or Aperture) = Diagonal Measurement x 0.87

Q. Why do some lenses only work on certain projectors?

The most common reason for this is due to the physical internal and

external designs of the projector itself. For example, the position of theLCD panel or electronic components inside the machine is simply not

compatible with all lenses. The design of the outside projector cover canalso determine whether or not some larger lenses can be used with thatparticular projector model.

Q. Is it difficult to install a new LCD lens in a projector?

Installing a new lens is relatively simple. There is no disassemblinginvolved and no heavy electronics to take apart. In fact, many projectormanufacturers are now designing their projectors to make it easier to

remove the prime lens.

Installation instructions are included with each NuView lens sent out.

You can also find a complete set of instructions on our website (clickhere for online installation instructions). If you have any doubts,

contact your dealer for the name of an authorized service center ortrained professional in your area, or you can contact the Navitar directly.

Q. Will I lose all of my remote control features?

All NuViewlenses are manual lenses, that is, you must focus or zoomthe lens by hand (your power zoom and power focus functions will bedisabled). If your projector has a lens shift function, you will retain thisfeature. For fixed installations, the picture size and focus need to be set

only once and readjustment is not necessary. Set it and forget it!

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Q. At what distance will my lens focus?

Most NuViewlenses will focus as close as 3 to 4 feet in front of the

projector and all lenses are set to focus to infinity, therefore focusing atlong distances will not be a problem.

Q. What do these terms mean?

Zero OffsetMost LCD projectors have a built-in angle of projection,usually upwards a few degrees. A "zero offset" or "on axis" lens projects

straight out in front, so it is necessary to place the projector in aposition that is perpendicular to the center of your screen. This is

typically the case when using wide-angle and fixed lenses.

MCZ (in the catalog #)Literally, it stands for Multi-Coated Zoom(MCLis for Multi-Coated Lens). This is a new manufacturing process

developed by Navitar, in conjunction with our sister company, NavitarCoating Labs, Inc. The process increases the brightness, contrast ratioand color saturation of our "Xtra Bright" lenses.

Prime LensThe "prime lens" is the factory installed, manufacturers

lens that comes with your projector.