Wide angle setting causes fisheye?

Discussion in 'SJ7 Star' started by magicbob, Jan 26, 2018.

  1. magicbob

    magicbob New Member

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    Hi,

    I recall reading that a wide angle camera causes the fisheye effect.

    If that is correct, and because I don't have the distortion setting with 1.18, can I turn off the wide angle effect to lose the fisheye effect?

    If so, where is that?

    Would I only lose the wide angle and otherwise the quality would be the same?

    Thank you for your help.

    Bob
     
  2. Sulev Svilponis

    Sulev Svilponis Elite

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    Wide angle camera is not neccesarily with the fisheye effect. It depends on the lens. If the lens is a fisheye type lens, then it has the fisheye effect. If the lens is rectilinear, then it has not the fisheye effect.
    It is not possible to switch between those types, unless you physically change the lens. But it is possible (to some extent) to correct curvature of the fisheye effect by image processing (in camera function: DISTORTION CORRECTION). This causes always some losses in picture information (and quality), so I think, that for better quality it's wise to do any distortion correction during the postprocessing only.
     
  3. RBEmerson

    RBEmerson Humbled by events

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    The Lens Correction menu option in V1.20 will end the "curved poles" seen in fisheye imagery. The perspective at the edge of the image will still look ...well... different. There's just no way to avoid some distortion. It's all in the geometry of trying to make a wide, spherical space fit on a flat image (trust me, it's like that, but the explanation of why that's so involves trigonometry). Using narrower fields of view (the FOV option) will help but, of course, you're no longer looking at a wide field of view. You can have wide and distortion, or narrow and no distortion, but you can't have wide and no distortion.
     
  4. Sulev Svilponis

    Sulev Svilponis Elite

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    Is there really the Lens Correction menu option in V1.20? The User Manual doesn't mention it. Distortions could be reduced from the DISTORTION CORRECTION menu option.
     
  5. RBEmerson

    RBEmerson Humbled by events

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    Distortion Correction remaps the image to minimizing the "fisheye" effect. However the size of the image is reduced, as is demonstrated elsewhere in the forum.

    The option is in the tools menu, between Light Frequency and Image Rotation. It is not available for all resolutions, notably 4K.
     
  6. Jason

    Jason Moderator

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  7. magicbob

    magicbob New Member

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    Are there simarally priced action cameras which don't have wide angle lenses and so don't have the fisheye effect and don't require editing?
     
  8. Damian Holt

    Damian Holt Moderator

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    You can change the field of view in certain resolutions to narrow which helps to remove the Fisheye effect. Also distortion correction does a pretty good job at correcting the issue.
     
  9. magicbob

    magicbob New Member

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    Where do I go to change the FOV and what setting(s) will do this?

    No one yet replied if there are similarly priced action cameras which don't have wide angle lenses and so don't have the fisheye effect and don't require editing?
     
  10. Damian Holt

    Damian Holt Moderator

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    2F219BD4-5D51-48C0-9C45-66229EC93590.jpeg You change FOV in settings, it’s an option 2 or 3 down from resolution.

    Attached is the available resolutions that FOV can be changed in.

    As for other cameras I would have thought the majority would have a similar option. I’m fairly sure gopro does. If your looking for a camera that just had a fixed narrow FOV then try googling it.
     
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  11. Sulev Svilponis

    Sulev Svilponis Elite

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    It is possible to change attached lens. Search for M12 cctv rectilinear or low distortion lenses. Those are relatively cheap.
    One sample is:
    https://m.alibaba.com/product/60705...53732eaTNiE93&detailId=60705533189&redirect=1

    Pay attention on presence of the IR cut filter. Lenses without the filter will give wrong colors.
    Another thing, the original lens for the SJ7 has FOV ca 65 degrees. It has ca 2.5mm focal length. By replacing it with above mentioned 5mm lens, you will loose 50% of your current FOV.
     
    Last edited: Jan 31, 2018
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