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Throw distance definition

Discussion in 'Projectors, Screens & Video Processors' started by lennyb, Nov 12, 2002.

  1. lennyb

    lennyb
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    I am trying to figure out how to get the image size for a projector for a given throw distance. The problem I have is finding a definition of what throw distance is.

    Some web sites state that it is the ratio of throw distance against the image diagonal

    http://www.proxima.com/support/FAQthrowratio.asp
    http://www.evertech.net/Main/Sales/Communications/Projection/ProjectionTerms.asp#throwratio
    http://faculty.goucher.edu/leharris/lcdprojectors.htm#throwratio

    Other web sites state that the throw ratio is the throw distance against the width of the image.

    http://www.sanyo.com/business/presentation/techtips_15.html
    http://www.audiogeneral.com/Products/Glossary.html

    What is the correct answer?



    Also, if you look at the specification for an InFocus LP530

    Min Throw distance: 1.5m
    Throw Ratio 1.2:1

    The table of projection distance /image sizes states that a throw of 1.5m will give a maximum image diagonal of 1.1m and a minimum image diagonal of 0.9m.

    Using the equation

    Diagonal = distance /throw ration

    Gives us a diagonal of 1.25.

    How do they calculate their figures?

    Thanks in advance
     
  2. RichardH

    RichardH
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