Microsoft KB Archive/172829

INFO: Converting SOFTIMAGE 3D Camera’s Field Of View

PSS ID Number: Q172829 Article last modified on 09-05-1997

IRIX:2.66,3.0,3.5,3.51,3.7; WINDOWS NT:3.0,3.01,3.51,3.7

IRIX NT WINDOWS

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The information in this article applies to:

 Softimage 3D for IRIX, versions 2.66, 3.0, 3.5, 3.51, 3.7 == Softimage 3D for Windows NT, versions 3.0, 3.01, 3.51, 3.7 == 

= SUMMARY =

The SOFTIMAGE 3D camera’s field of view (FOV) is measured with the vertical lens angle, not the standard horizontal lens angle. Therefore, if you need to use the SI3D camera data for other purposes, you must first convert the vertical lens angle to the horizontal lens angle and then use the data.

= MORE INFORMATION =

To get the proper FOV for a particular shot you must know: lens focal length (55mm, 80mm, etc.), media (35mm film, or 16mm film), and type of camera (vistavision, 4-perf, still, etc - because one type of film is used differently in different cameras).

Use the following formula to calculate the horizontal and vertical angles when you know the focal length, and either the width, or the height of the exposed surface of the film:

Horizontal angle = 2 * arctan (width/(2 * f))

Vertical angle = 2 * arctan (height/(2 * f))

For the conversion formula when you do not know either the horizontal angle, or the vertical angle, please see the following article in the Microsoft Knowledge Base:

ARTICLE-ID: INFO: Converting The SOFTIMAGE 3D Camera Angle TITLE : Q167242

The following table lists the vertical angle for the most commonly used 35mm SLR still camera lenses:

Lens SOFTIMAGE vertical angle —- ————————

24 mm -> 53 28 mm -> 46 50 mm -> 27 85 mm -> 16 105 mm -> 13 150 mm -> 9 210 mm -> 6

A great source of information is the American Cinematographer Manual. It contains tables with the typical FOVs for different cameras and lenses. To use these in Softimage, you would divide the numbers by the aspect ratio (to get the vertical field of view). You can order a copy of the manual from the following source:

Opamp Technical Books www.opampbooks.com 1(800)468-4322

= REFERENCES =

If you have any questions concerning the information contained in this article, contact support@softimage.com by e-mail.

= Additional query words: si si3d si3dcam =

Keywords : si si3d si3dcam Version : IRIX:2.66,3.0,3.5,3.51,3.7; WINDOWS NT:3.0,3.01,3.51,3.7 Platform : IRIX NT WINDOWS Issue type : kbinfo ============================================================================= Copyright Microsoft Corporation 1997.