What exactly causes this photo distortion?

Discussion in 'Digital Photography' started by Murgatroyd, Sep 13, 2016.

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  1. Murgatroyd macrumors member

    Murgatroyd

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    #1
    When I tap to hold the screen for the iPhone 6s+ auto-focus to kick in is what causes this distortion where the buildings converge, I thunk . But sometimes lighting is too dim or blown-out. Is there a solution other than not utilizing auto-focus?

    T'anks


    New York, NY - Centre St, September 12, 2016.jpg New York, NY - Flatbush Avenue Ext, September 13, 2016.jpg New York, NY - Washington St, June 12, 2016 2.jpg
     
  2. bent christian Suspended

    bent christian

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    #2
    What I see looks like the result of a corrected barrel distortion of the wide angle iPhone lens. I don't understand why it would be occurring with auto-focus only. Do you have some sort of app installed that corrects lens distortion?
     
  3. MCH-1138 macrumors 6502

    MCH-1138

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    #3
    The buildings appear to converge because of perspective distortion. Think of the buildings like a long, straight road heading off to a vanishing point on the horizon. The more you tilt the camera up, the more exaggerated the convergence will be. If the plane of the camera is kept parallel to plane of what you are photographing (i.e., the buildings), you won't have the converging lines. Of course, that would also affect the composition. There are software tools available to remove or correct for the perspective distortion.

    It has nothing to do with the focus-lock or exposure-lock functions.
     
  4. dwig macrumors 6502

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    #4
    The tops of the buildings are further away from the camera and hence they reproduce smaller than the closer portions at ground level.

    The only influence the barrel distortion correction has is that the vertical edges of the buildings are straightened and the perspective effect may become more noticeable than when the edges are curved.
     
  5. robgendreau macrumors 68040

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    #5
    Yeah, you need a tilt shift lens (heh).

    I think Snapseed has a tool to correct some perpective problems, but with some photos it's just not possible with an iPhone camera.
     
  6. MCAsan macrumors 601

    MCAsan

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    #6
    Lightroom and other post processing apps have all manner of perspective correcting features.
     
  7. jerwin macrumors 68000

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    #7
    Wait for iPhone8-Plus. I've heard that it comes in a bevy of cool new colors, too.
     
  8. MCAsan macrumors 601

    MCAsan

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    #8
    You don't fix perspective problems in camera body.....you can prevent it "in lens" with the tilt shift on an interchangeable lens camera....or...in post processing by stretching part of the image.
     
  9. sarge macrumors 6502a

    sarge

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    #9
    That first building isn't distorted, it's just a Gehry design.
     
  10. Murgatroyd thread starter macrumors member

    Murgatroyd

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    #10
    I look at photographs of old and this effect doesn't appear with whatever camera back then. I assume it's the spherical lens causing the distortion and the electronics of the camera goes bonkers. If a quality camera costing thousands did this today I'd have to wonder what all those engineers have been doing to not have found a functioning system to rectify the situation. It's a close range, fish-eye effect an algorithm would correct, no?

    So it goes. I'll fire up Affinity Photo and work the Mesh tool later. Give it a whirl.
     
  11. EiriasEmrys macrumors member

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    #11
    If your talking about how the perspective is exaggerated here, thats standard wide-angle distortion from a wide-angle lens. It has more to do with image optics than the camera itself. The lens is very wide as it is meant to be able to capture most common use scenarios that most users would need it for. Group photos in tight spaces, landscapes, selfies, etc.

    Old cameras would have had lenses capable of doing the same. If you want buildings that have no distortion, not only would it be near impossible at the angle you took them, even with a longer lens, it would be unrealistic to how we see the world. We see with a similar "wide lens" and similarly while a building is the same diameter all the way up, our brain is the part that tells us that, we see it as a receding shape that gets smaller at the top. Images your thinking of without that distortion would need to be taken with a long lens at a perpendicular angle, rather than from the base of the building.
     
  12. MCH-1138 macrumors 6502

    MCH-1138

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    #12
    You would see the exact same converging lines if you took a photo from the same location with any camera and lens with an equivalent field of view to what you used. I believe the iPhone 6s Plus camera has a field of view similar to a 29mm lens on a full-frame camera. So if you spent $$$ on a top-of-the-line DSLR and another $$$ on a top-of-the-line 24-70mm f/2.8 zoom lens, zoomed out to 29mm and shot from the same spot with the same composition, the images from the "quality camera" would have the exact same converging lines.

    As others have indicated, your alternatives for avoiding converging vertical lines are (1) change your composition (so you aren't tilting the camera up or down), (2) shoot using a tilt-shift lens (not really an option for a iPhone), or (3) post-processing correction in your software of choice.
     
  13. Murgatroyd thread starter macrumors member

    Murgatroyd

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    #13
    Affinity Photo, Mesh Tool …, seems odd the camera software doesn't yet have these options, is all. A simple (or not so simple? bologna! :) algorithm thang to option to, somehow.
     

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  14. mixel macrumors 65816

    mixel

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    #14
    https://itunes.apple.com/gb/app/skrwt/id834248867?mt=8 is the best perspective correction software I'm aware of on iOS.. Someone up there mentioned Snapseed which will probably do it well too. :)

    The photos don't look wrong to me though, they're what I'd expect from a tiny camera of this sort.
     
  15. PinkyMacGodess macrumors 601

    PinkyMacGodess

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    #15
    I saw part of a lecture about phones and cameras and why phones don't make good cameras.

    Their opinion is 'The lens is small, the distance between the lens and sensor is too short'. There is no way, according to the lecturer, that you can end up with 'good' pictures with those kind of dimensions.

    Personally I think some of this is the really old (like me) argument between tube and transistor amps. I worked at an 'audio store' and had people come in often to try to argue with me about the various 'problems' with transistor amps.:rolleyes: We carried Macintosh amps, but half of those arguing for tubes, didn't want to prove it and actually BUY one.o_O These 'Jihad' arguments are a grand waste of time, but humorous at times. I have two DSLR cameras and use one for my telescope, and the other just sits in a carry bag.:(

    Could this be the 'small lens/short length' effect? Perspective?

    The weird/cool ones are the ones that are artifacts of the scan rate of the sensor.
     
  16. Precision Gem macrumors 6502

    Precision Gem

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    #16
    Any camera with the film plane or sensor tilted at an angle would produce the same type of distortion. Only a camera where the film plane can be completely perpendicular to the earth, and the lens shift can eliminate this effect. This is one reason why a camera in any phone or most any other camera can never replace a view camera for truly professional results.
     
  17. leart78 Suspended

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    Nov 17, 2013
    #17
    I own many iPhones... till iPhone 4S I was able to take photos of my bike and wheels to look round, with my iphone 5 on ios 6.0.1 I just can't .. I'll try with my 6s+
     
  18. Alexander.Of.Oz macrumors 68030

    Alexander.Of.Oz

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    #18
    This fella answered your query above, but here is a link to how that works.

    Ummm, if I understand you correctly, your wheels are no longer round? If so, just get your iPhones lens perfectly on centre of the wheel, by looking at the screen and moving the iPhone up, down, left and right, until the wheel is perfectly round. You will need to hold it on a perfectly parallel plane with the wheel too.
     
  19. Nathan King macrumors member

    Nathan King

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    #19
    Ahh, architecture...my specialty. As mentioned, it is due to your camera's sensor not being parallel to the side of the building (i.e. pointing the camera upward and not perfectly horizontally). To summarize, you have three options for correcting this:
    1. Move further away from the building, keep the camera level and crop the bottom half off of the image. Obviously, this causes an enormous loss in resolution and angle of view.
    2. Frame loosely and use software to correct the distortion. The software is correcting the image by essentially pulling the bottom inward and back. You'll end up with proper verticals, but the building will look squatter than it should. Essentially, you're trading one form of distortion for another.
    3. Purchase and learn to use a tilt-shift lens. This yields the most geometrically correct image with the highest resolution; however, such lenses are expensive, slow to use and have a learning curve.
    An image at 24mm with 10mm of shift and 1.5 degrees of tilt:

    [​IMG]
     
  20. kenoh macrumors demi-god

    kenoh

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    #20

    Lovely picture. Lovely architecture on that one. If you are into lovely buildings then Glasgow has quite a few beautiful buildings. The problem is that they usually stuck up some modern monstrosity beside it. Thats a bank right?
     
  21. Nathan King macrumors member

    Nathan King

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    #21
    It was built in 1889 by the well-known firm of McKim, Mead and White. The rusticated Massachusetts brownstone on the bottom three floors, ornate terra cotta trim and bronze eagle above the high arched entrance are the most notable features. It was originally home to New York Life Insurance Company but was purchased by Omaha National Bank in 1906. Oddly enough, it is now home to Kutak Rock LLP, a law firm. It is unfortunate that almost none of the original interior remains. This building has an exact twin in Kansas City. That's probably more than you cared to know. :)
     
  22. kenoh macrumors demi-god

    kenoh

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    #22
    Not at all thats really interesting. I like the history of things.
     

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