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Thread: RZ67 digital backs lens crop?

  1. #1
    Senior Member Pemihan's Avatar
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    RZ67 digital backs lens crop?

    I really have a hard time figuring this out...

    If I use my IQ160 on a RZ67 what will the lens crop be compared to using the back on the DF+ or my Cambo?

    Will a 120mm image have the same angle of view on all three systems?

    Thanks
    Peter
    Peter
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    Senior Member Stefan Steib's Avatar
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    Re: RZ67 digital backs lens crop?

    "....Will a 120mm image have the same angle of view on all three systems?..."

    Yes - exactly ! Focal length is focal lenght.

    Maybe to clear this you should get an app for iPhone which explains this quite good: It´s called angle of view. Highly recommended !

    Regards
    Stefan
    because photography is more than technology - and " as we have done this all the time "
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    Senior Member Pemihan's Avatar
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    Re: RZ67 digital backs lens crop?

    Yes focal lenght is focal lenght but the angel of view can be different, eg if you use a 44x33mm vs a 53.9 x 40.4mm back.

    I will check out the Angle of View app, thanks.

    Peter

    Quote Originally Posted by Stefan Steib View Post
    "....Will a 120mm image have the same angle of view on all three systems?..."

    Yes - exactly ! Focal length is focal lenght.

    Maybe to clear this you should get an app for iPhone which explains this quite good: It´s called angle of view. Highly recommended !

    Regards
    Stefan
    Peter
    My website

  4. #4
    Senior Member Pemihan's Avatar
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    Re: RZ67 digital backs lens crop?

    I'll rephrase my self:

    Will an image shot with a 120mm lens on all three systems have the same angle of view or will there be a crop factor to consider?
    Peter
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    Re: RZ67 digital backs lens crop?

    Focal length of the lens and the size of the sensor involved are the only things that matters.

    If you use the same back on multiple bodies, each time with a 120mm lens then the framing of the scene will be identical on all three.

    The light tight box in the middle does not matter.
    Last edited by dougpeterson; 13th September 2014 at 11:23.
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  6. #6
    Senior Member Pemihan's Avatar
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    Re: RZ67 digital backs lens crop?

    Ok, got it, thanks Doug.
    Some times my brain runs in circles and today was one of those days..
    Peter
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    Senior Member Stefan Steib's Avatar
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    Re: RZ67 digital backs lens crop?

    "...Yes focal lenght is focal lenght but the angel of view can be different, eg if you use a 44x33mm vs a 53.9 x 40.4mm back...."

    That´s true but you asked what will happen when you use an IQ160 on different bodies with 3 different 120mm lenses. :-)

    One thing that is nearly sure (though it doesn´t have anything to do with Physics) is these 3 images will NOT be identical.....
    because a marked 120mm lens normally is allowed to differ +- 10% by Iso in focal length !!! Zeiss for example limits their lenses to 5 % but this means unless you got "matched" equal focal length exemplars you might even end up with different image sizes using 3 of the same lenses on the same body !!!

    ....and now you know the rest of the story.....

    Regards
    Stefan
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    Senior Member ErikKaffehr's Avatar
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    Re: RZ67 digital backs lens crop?

    Hi,

    You are right, but I don't think there is a significant variation in focal length within a single lens line, tolerance are probably quite tight.

    It is well possible that the exact focal length is say 107.5 mm, but it may be sold as either 105 mm or 110 mm. But most samples may be within say 107.2 and 107.8 mm.

    Another factor may be the optical construction may be changed over time. Perhaps a type of glass is replaced with another type having different optical properties.

    I used to muse myself with the 90-110 zoom that actually is a prime lens :-)

    Best regards
    Erik

    Quote Originally Posted by Stefan Steib View Post
    "...Yes focal lenght is focal lenght but the angel is these 3 images will NOT be identical.....
    because a marked 120mm lens normally is allowed to differ +- 10% by Iso in focal length !!! Zeiss for example limits their lenses to 5 % but this means unless you got "matched" equal focal length exemplars you might even end up with different image sizes using 3 of the same lenses on the same body !!!


    Regards
    Stefan

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    Senior Member Stefan Steib's Avatar
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    Re: RZ67 digital backs lens crop?

    Hi Erik

    Try it and measure it. You will be astonished......

    I had to learn it the hard way, as we once had a customer who bought 2 of our 40mm lenses to use them on a book reproduction system. It didn´t work, because the cameras were mounted exactly on same mirrored positions and the lenses were NOT identical and more than a little.

    The reply of Zeiss is what I told you in the last post.

    For all complex lenses which are calibrated at mounting this is the same.

    The one exception that I know of are the newer Canon lenses like the 17mm and 24mm TS-E which use pressed aspherics.

    Greetings from Germany
    Stefan
    because photography is more than technology - and " as we have done this all the time "
    facebook:hcam.de - www.hcam.de - www.hartblei.de

  10. #10
    Senior Member ErikKaffehr's Avatar
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    Re: RZ67 digital backs lens crop?

    Hi,

    OK, I am astonished and stand corrected!

    Best regards
    Erik


    Quote Originally Posted by Stefan Steib View Post
    Hi Erik

    Try it and measure it. You will be astonished......

    I had to learn it the hard way, as we once had a customer who bought 2 of our 40mm lenses to use them on a book reproduction system. It didn´t work, because the cameras were mounted exactly on same mirrored positions and the lenses were NOT identical and more than a little.

    The reply of Zeiss is what I told you in the last post.

    For all complex lenses which are calibrated at mounting this is the same.

    The one exception that I know of are the newer Canon lenses like the 17mm and 24mm TS-E which use pressed aspherics.

    Greetings from Germany
    Stefan

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    Senior Member Steve Hendrix's Avatar
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    Re: RZ67 digital backs lens crop?

    Quote Originally Posted by ErikKaffehr View Post
    Hi,

    OK, I am astonished and stand corrected!

    Best regards
    Erik

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