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Thread: why picture turn out concave ?

  1. #1
    Senior Member erictan8888's Avatar
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    Default why picture turn out concave ?

    hi,


    i took this shot of the city skyscrapers and it turned out kind of concave outwards....
    i find that i quite like this kind of looks....

    would like to know how this was done? (cause i can't remember what setting.... as far as i remember, i did not doing anything unusual-- yet shot turned out like that)

    has it got to do with tripod angle, camera angle or what ?
    hmm... cannot replicate this now, so would like to know how to do it...

    comments for pic would be appreciated.... thanks


    Hope to learn from everyone here....

  2. #2
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    i suppose the correct term is pincushion. ur using a wide angle lens?

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    Not pincushioning. It would be a lemon if it pincushion to this extent.

    It is instead perspective distortion and is due to physics and nothing to do with the lens. Search on the net for the definition.

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    oops =X

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    ur camera is tilted. use photoshop to correct the perspective.
    sigh.

  6. #6

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    Quote Originally Posted by Clown
    ur camera is tilted. use photoshop to correct the perspective.
    yup think its the perspective can be corrected in photoshop~ saw an article somewhere. Will post a link if i see it again. Its usually more dramatic with wide angle lenses IIRC

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    Check out articles under megaweb's gallery on CS... there's a perspective distortion correction article.

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    as mentioned, what you have is perspective distortion. the camera is tilted up and you'll get "converging" verticals.

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    Senior Member erictan8888's Avatar
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    so is this an error in the camera positioning if the camera is tilted up ?

    or is this kind of shot "acceptable" in terms of photography?
    it seems that most users are mentioning about correction....
    i mean is it something that photographers avoid ?

    btw, was using a 12-24mm lens...

    pls advise... thanks
    Hope to learn from everyone here....

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    it's not an error per se. just what you want to capture. if you want to capture all verticals as verticals, position the camera properly.

  11. #11

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    Its keystoning. You get this when focal plane is not parallel to subject plane.

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    Senior Member +evenstar's Avatar
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    Use perspective cropping in Photoshop...and your problem is cured...

    My try (cropped from your image)
    eat. drink. shoot

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    Senior Member dennisc's Avatar
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    i think the winds was blowing thats why the buildings swayed to the back.

  14. #14

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    Keystone distortion is not a bad thing if u know how to make use of it. But as shown in this photo, it's neither here nor there, the buildings looks like going to collapse, thus not good.

  15. #15

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    Hmmm, thats why for people who're doing architecture Canon has this series of "tilt-shift" lenses to correct keystoning?

  16. #16

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    Just go and get a Tilt and Shift lens.

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    Note that there is little point for him to get a T&S/PC lens if he shoots occationally, unless he is feeling rich or anyone of the recommenders buy from him. The widest T&S from Canon is the 24mm T&S cost S$2950 (list) and with the crop, becomes similar to a 38mm. Nikon's PC 24mm is significantly cheaper, at $2110 (list, 28.5% cheaper) but gives a 36mm angle of view.

  18. #18
    Senior Member erictan8888's Avatar
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    another pic taken with the same lens on the same day...



    this has less concave effects....i guess it is because the camera not tilited upwards... am i right ?

    thanks
    Hope to learn from everyone here....

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    2 things to note when using ultra wide angle lenses:

    1. Wide angle lenes when shooting at subjects that are more ore less than perpandicular (90 deg) will form what we call converging verticals where the vertical lines seems to be converging towards the top or bottom.

    2. So keep the central object as close to 90 deg so as to avoid this. Nikon and Canon use to make a tilt lens when the lens is shifted to accomodate or avoid this tilting effect.

    That's why we don't use wide angle lens for portraiture, people get big legs or heads. LOL

  20. #20
    Senior Member erictan8888's Avatar
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    what is considered ultra wide lens?
    12-24mm considered also right ?

    normally until how many mm than not within the ultra wide lens classification ?

    thanks
    Hope to learn from everyone here....

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