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Troubleshooting my BMCC Metabones Speedbooster and Sigma 18-35mm

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  • Troubleshooting my BMCC Metabones Speedbooster and Sigma 18-35mm

    I have a Sigma 18-35 1.8 Nikon mount lens but it seems like it has lost its F1.8.. images seem darker now. When I look through the lens from back to front it looks like the aperture has closed to less then half the diameter of a penny. Is that even possible isn't the aperture fixed? I have to have my Speedbooster on 7 to use it ISO on the camera 400 for a lit scene 3 point light..

    If you look through the Sigma like your camera how big is the opening?
    Any recommendations on how to troubleshoot this?


  • #2
    In the mount of the lens is a little tab that sticks out. This is the lever that controls the aperture. Move it with your finger. It should open and close the aperture. If, when you let go of the tab, the aperture does not close all the way down (f/16) you probably need to get the lens serviced as the sprint that closes the aperture must be damaged. It is normal behaviour for any nikon lens to close the aperture when the lens is removed from the camera.

    When mounting on the Speed Booster turn the ring on the adaptor to 7. Now when you open the aperture to 0 the lens should open fully to f/1.8.
    Adam Roberts