undesired change in as it passes from the input to the output of some system or device. DOES mention system input versus output, but cites no author or published source other than the Columbia Encyclopedia, below, I will edit it slightly to be non-system specific ( audio versus imaging ): See also and which sadly do not grock that they are comparing input to output, duh. Please edit subsequent sections from the first paragraph to ALWAYS consider the definition of system distortion as a comparison of input to output. If you get close enough to the resulting printed image, relative in distance that the photographer was from the subject, such that the photographer's angle of view and the print-viewer's angle of view are the same, then the audience will have the same experience of the subject, NO DISTORTION. But wide angle lenses distort everything, especially close up. If the audience positions themselves such that they see the presentation image from proportional distance resulting in an identical angle of view to the photographer's capture angle of view, then there is no distortion.
It must be compared to the experience of the audience of the resulting presentation image, the system output, in order for there to be a discussion of system distortion, in this case, system perspective distortion. It must be compared to the system output before assessing system distortion, if any. That is, according to the definition of distortion, we are comparing input to a system, to output from a system, and in this case, the input is the photographer's viewpoint or perspective, and the output is the audience's viewpoint or perspective of the presentation image.īUT no one is following that criteria when subsequently exploring conditions where system perspective distortion may be observed, explained, and intentionally employed or avoided if desired.Īn image captured with a wide angle lens is not distorted, it can't be, because it is only the system input.
Perspective distortion is determined by the relative distances at which the image is captured and viewed, and is due to the angle of view of the image (as captured) being either wider or narrower than the angle of view at which the image is viewed, hence the apparent relative distances differing from what is expected. STOP - We're forgetting viewing the presentation image as a necessary component of system perspective distortion 5 This article is less correct than before.1 STOP - We're forgetting viewing the presentation image as a necessary component of system perspective distortion.
#CAMERA LENS DISTORTION BIG NOSE ISO#
ISO 17850 describes this method in detail. If deriving a single number from the local geometric distortion, the maximum distortion measured for any of the image's geometric structures is the one that is reported. H is the nominal distance of the dot from the image center based on an expanded regular grid. H* is the distance of the dot from the image center The distortion is then measured using the following formula: Figure 6: H-values for determination of the local geometric distortion This grid is expanded to the whole image and defines the nominal positions for each of the structures. Then you can calculate a regular grid based on the geometric positions of the nine structures (3x3) in the center of the image. When measuring the local geometric distortion, we assume that the distortion close to the optical center is zero.
Keep in mind that when you need to address a specific image height, the local geometric distortion is more reliable. In other words, we need a function for the distortion to correct the distortion in image processing. The local geometric distortion method is utilized when a single number for the distortion is not sufficient. Local geometric distortion method (ISO 17850) The sign for Dlinei represents the higher absolute value of either the horizontal or the vertical line distortion. This method is compliant with the process described in EBU Tech 3249 3249 3. The ratio of the bending over the height of the image multiplied by 100 is the percentage of picture height distortion. The bending of a straight line in the original image is quantified at the image's top edge (see figures below).
#CAMERA LENS DISTORTION BIG NOSE TV#
The TV distortion method is essentially a system that shows a steadily increasing distortion from the image center to the corners. Figure 2: The TE260 (left) dot chart and the TE251 grid chart are two popular charts for measuring distortion