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Thread: Zoom lens coverage at telephoto end

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    Zoom lens coverage at telephoto end

    So no c-mount zooms work for full coverage at the wide end. However, are there any zooms (fast c-mount or otherwise) that work on the entire m4/3 sensor at the wide end ? I am hoping for f1.4 or thereabouts at 100mm and uip (i.e. 200mm equivalent) to allow for a fast tele lens.

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    Re: Zoom lens coverage at telephoto end

    Yes!
    1.5 18-90mm Sun or Cosmicar or possibly many other names. Very large and heavy. You finally drag it out of me.
    The last one I saw on the web was for sale from Canada. No vignetting at all, possibly it covers 35mm?

    Remember that some of the 2x lenses, often not c mount, where the doubler is switch enabled, will work with any m4/3 which has digital zoom albeit with some degradation. These can be very good with extended range and f1.4 or so. But as they will not work with my ep1 which does not have digital zoom, I cannot give a first hand account.

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    Re: Zoom lens coverage at telephoto end

    I some some of the B3 B4 mount lenses and have adapted them. However the 2x doubler adds 2 stops. So, a 1.7 lens become 3.4

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    Re: Zoom lens coverage at telephoto end

    Edit:- 2 stops from 1.7 would be
    2 = (x/1.7)^2
    x=1.7 * 1.14 = 1.94

    Hmm.. Not too bad here. I have a number for Fujinon lenses at that speed. Pics to follow soon.

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    Re: Zoom lens coverage at telephoto end

    I could not locate a 18-90mm zoom. However there is a Sun Cosmicar 22.5-90mm f1.5 zoom. Are we talking about the same lens ?

    Quote Originally Posted by Pat Donnelly View Post
    Yes!
    1.5 18-90mm Sun or Cosmicar or possibly many other names. Very large and heavy. You finally drag it out of me.
    The last one I saw on the web was for sale from Canada. No vignetting at all, possibly it covers 35mm?

    Remember that some of the 2x lenses, often not c mount, where the doubler is switch enabled, will work with any m4/3 which has digital zoom albeit with some degradation. These can be very good with extended range and f1.4 or so. But as they will not work with my ep1 which does not have digital zoom, I cannot give a first hand account.

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    Incorrect math

    3 = (x/1.7)^2
    x=1.7 * 1.73 = 2.94

    So I have a f3 zoom.

    Quote Originally Posted by zcream View Post
    Edit:- 2 stops from 1.7 would be
    2 = (x/1.7)^2
    x=1.7 * 1.14 = 1.94

    Hmm.. Not too bad here. I have a number for Fujinon lenses at that speed. Pics to follow soon.

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    Re: Zoom lens coverage at telephoto end

    Zcream
    Sorry, you are correct. 4x zoom to 90mm.

    Surely 2 stops is 2x 1.7= 3.4?

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    Re: Zoom lens coverage at telephoto end

    Hi Pat. I think the stops are the square of the ratio. So a f2 lens need 4 times more light than an f1 lens. I bought the Sun cosmicar from a seller in Canada. waiting for it to arrive.

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