![]() What you are describing are fundamental phenomena. Have a look at the images for conic sections. Just imagine that you are looking at the cone from the position of the ball, the sensor will be at an angle to the line from you through the focal point. The further from the center of the image the ball is, the less it is like a circle. It will only be a circle if the ball is exactly in the center of the image. The intersection of that cone with the sensor will be an ellipse. A line from the visual boundary of the ball to the focal point is a line through the focal point that is tangential to the ball. This line will intersect (the plane containing) the sensor in one point, this point will be the corresponding point in the image. ![]() Now for any point of an object that you photograph, just consider the line through that point and the focal point. There is one focal point (the distance of that point from the sensor is the focal length). Indeed let us assume an idealised perfect lens. The problem with the outline of the ball not being a circle is not a sign of pincushion or barrel distortion. Why isn't this done? Pictures are starting to look rather ridiculous in the last crop of wide-angle lens smartphones, and the problem applies pertinently to the one most common types of photos: the groupife. Other smartphones don't fare much better.Īutomatic distortion correction of the sort done in post-processing should be relatively fast because the camera parameters are fixed, and the code could be highly optimized in the camera firmware.īut even if correction were slow, it could be queued up for later, yet still automatic. ![]() ![]() The exercise ball is quite spherical in reality. Given that smartphones have so much processing power nowadays (Nvidia GPUs, for instance), and that their pincushion distortion is easier to correct than the extremely wide-angle fish-eye lens in the GoPro, why don't smartphones automatically correct this distortion and the skew it produces in photos?īelow is a Sony Xperia Z5 photo illustrating the extreme distortion. I've previously asked why the GoPro doesn't automatically correct for the fisheye distortion, and this question is related, but different: ![]()
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