Can aperture specifications change using adapted lens?

Discussion in 'Adapted Lenses' started by Crdome, Apr 29, 2012.

  1. Crdome

    Crdome Mu-43 Hall of Famer

    Sep 11, 2011
    West Central Indiana
    Chrome
    Optic qualities change with adaptive glass since only the central portion of the lens is projecting on to the sensor. Larger apertures are related to larger glass diameter, can this change the stated aperture of the lens, or does this remain a function the Field of Depth?
     
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  2. dhazeghi

    dhazeghi Mu-43 Hall of Famer

    Aug 6, 2010
    San Jose, CA
    Dara
    Aperture is a physical measurement. So long as nothing in the adapter blocks the rear of the lens, the aperture does not change. Depth of field does not really change either (technically, smaller pixels do make a difference, but a minor one). What changes is the focal length of the lens needed to get a particular angle of view.

    For example, if you put a 50mm f/1.8 lens on a 64MP FF camera, shot it at f/1.8 and then cropped to the center 50%, you'd have exactly the same effect as shooting that lens on a 16MP 4/3 camera. But by cropping, you're now looking at an image with the same framing that you would use a 100mm lens for on the FF camera.

    (Obviously there are no 64MP FF cameras today, so in practice the pixels in FF cameras are magnified less, which does have minor implications for DoF).

    DH
     
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  3. Crdome

    Crdome Mu-43 Hall of Famer

    Sep 11, 2011
    West Central Indiana
    Chrome
    Thank you. I now generally understand the concept. My question was inspired as I pondered over this big piece of glass: 9 1/2" f/4.5 - f/64. Assuming it's 4x5 format I wondered what its 35mm equivalent was and its crop factor on m4/3. Obviously it would be ridiculous to adapt, but could you shed any light on these questions. I love those iris blades!!!

    Thank you


    Wollensak_Velostigmat.

     
  4. Hikari

    Hikari Mu-43 All-Pro

    Nov 26, 2010
    focal length is focal length. That would be like any 9 1/2 inch lens on a m4/3 camera. It would be just like any 240mm m4/3 lens

    Angle of view is related to focal length and sensor/format size. DoF is also a factor of format size.

    Crop factor is a marketing tool.
     
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  5. kinlau

    kinlau Mu-43 Top Veteran

    836
    Feb 29, 2012
    If I understand your question correctly, on 35mm, the equiv would be approx 70-75mm, or 35-40mm on m43, otherwise, what Hikari said.
     
  6. Crdome

    Crdome Mu-43 Hall of Famer

    Sep 11, 2011
    West Central Indiana
    Chrome
    Thank you. It was the equivalent I was looking for.
     
  7. songs2001

    songs2001 Mu-43 Top Veteran

    693
    Jul 8, 2011
    Aperture is actually a ratio. Since you crop of half, you have to account for that in your pictures.

    To find an equivalent look. Just double everything.

    A 25 1.4 lens will look like a 50 2.8 lens on a 35mm camera more or less.

    But as far as exposure, a 25 1.4 will let in as much light as a 50 1.4, 200 1.4, 600 1.4, well you get the point.
     
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  8. Crdome

    Crdome Mu-43 Hall of Famer

    Sep 11, 2011
    West Central Indiana
    Chrome
    Thanks Songs. Now I understand the ratio part.