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Nikon Z7's shutter curtain light diffraction

Discussion in 'Nikon Z Mirrorless Forum' started by makoto honda, Apr 17, 2019.

  1. makoto honda

    makoto honda

    72
    Nov 3, 2018
    The Nikon Z7's mechanical focal-plane shutter produces a strong vertical line(s) from the sun. I believe this is due to light diffraction -- the same phenomenon that produces a familiar "sun star." A sun star is due to the diaphragm blades of the lens aperture. This vertical line, I believe, is due to the horizontal edge of the shutter curtain. I used an Ai Nikkor 20mm f/3.5 for this test. I am showing 6 pictures from f/3.5 (wide open) all the way to f/5.6, f/8, f/11, f/16, f/22. As I close down the aperture, the sun star (7x2=14 lines) dominates and the vertical line becomes less noticeable. The ISO used was 64, and the shutter speed was 1/1500 sec. for the lens wide open, and slowing down accordingly for smaller apertures.

    I noticed this same diffraction phenomenon with my Nikon F3 some thirty years ago. It was a horizontal streak of line then for the F3 has a horizontally traveling focal-plane shutter (therefore a vertical curtain edge). I believe this is a general phenomenon for any camera, any brand. No-brainer solution to this problem is not to use a mechanical shutter - yep, turn on the SILENT mode .... The last 4 shots shown here were taken just that. The first is f/3.5 wide open, then f/5.6, f/8 and f/11.

    If I am to add, I cannot tell you how easy and painless it was to do this test with the "EVF" of the mirrorless! Under the blazing sun, my Z7's EVF finder looked exactly as you are looking at these pictures on your monitor right now. True, the sun is bright, but still it is just a pure white (value=255, no more). In the glass-prism viewfinder, the brightness of the sun would have been probably 1000 times stronger! Even with the tiny area of the sun in the wide-angle view, gazing at the finder for a long time may compromise your eyesight.

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    Last edited: Apr 17, 2019
    • Informative Informative x 1
  2. johnvanatta

    johnvanatta

    5
    Aug 29, 2018
    Oakland
    John Van Atta
    Nice work! I'd noticed the vertical line too, but never thought of the fully electronic shutter fix. That'll be a handy for sure.
     
  3. Interesting! I saw a blog note about the vertical line saying it was the lens and that did not make any sense to me. Your description of shutter curtain diffraction proves that it is not the lens.
     
  4. makoto honda

    makoto honda

    72
    Nov 3, 2018
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    I dug up my old slides taken by Nikon F3, or F2. The horizontal streak of line from the sun is visible ... The second one is an in-camera double-exposure. Since the aperture was closed down to probably f/16-f/22, the effect of the horizontal streak is not that obvious. The lens was probably Nikkor 28mm. Kodachrome-25.
     
    Last edited: May 3, 2019
  5. These are superb! Love the rich colors and contrast.
     
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