Note that the above photos are slightly distorted this is to emphasize that when the stitching software positions each image it adjusts for perspective, and that the amount of perspective distortion depends on that image's location relative to the vanishing point. For architectural stitches, such as the example below (120° crop from the rectilinear projection), this point is also clearly apparent by following lines into the distance which are parallel to one's line of site. The vanishing point is usually where one would be directly facing if they were standing within the panoramic scene. Most photo stitching software gives the ability to specify where the reference or vanishing point of perspective is located, along with the type of image projection.Ĭareful choice of this vanishing point can help avoid converging vertical lines (which would otherwise run parallel), or a curved horizon. Any parallax error in the near foreground may not be visible if each of these foreground elements are not contained within the overlap between photos. For panoramas taken without a panoramic head, parallax error may become large in foreground objects, therefore more accurate results can be achieved by only basing these on distant objects.
HUGIN PHOTO STITCHING MANUAL
When stitching difficult cloud scenes such as that shown above, this effectively combines the advantages of manual control point selection with those of automated algorithms.Īnother consideration is how far awayfrom the camera each control point is physically located. PTAssembler has a feature called "automatically micro-position control points," which works by using your selection as an initial guess, then looking to all adjacent pixels within a specified distance (such as 5 pixels) to see if these are a better match. In these situations automated control point selection may prove more accurate. The example below demonstrates a situation where the only detailed, rigid portion of each image is in the silhouette of land at the very bottom-thereby making it difficult to space the control points evenly across each photo's overlap region.
It is for this reason recommended to always capture some land (or other rigid objects) in the overlap region between all pairs of photographs, otherwise control point selection may prove difficult and inaccurate (such as for panoramas containing all sky or water). This means that basing control points on tree limbs, clouds or water is ill-advised except when absolutely necessary. The best control points are those which are based upon highly rigid objects with sharp edges or fine detail, and are spaced evenly and broadly across each overlap region (with 3-5+ points for each overlap). The example above shows a selection of four pairs of control points, for two photos within a panorama. With most photographs, best results can only be achieved with manual control point selection (which is often the most time-consuming stage of the software stitching process). Pairs of control points may be manually selected by visual inspection, or these may be generated automatically using sophisticated matching algorithms (such as Autopano for PTAssembler).
Panorama stitching software uses pairs of control points to specify regions of two camera photos that refer to the same point in space. STAGE 2: CONTROL POINTS & PHOTO ALIGNMENT PTAssembler incorporates a fully-automated one-click stitching option, in addition to providing for nearly all possible custom stitching options available in other programs.Īt the time of this article, other notable programs include those that come packaged with the camera, such as Canon PhotoStitch, or popular commercial packages such as Autostitch, Hugin Panorama Photo Stitcher, Arc Soft Panorama Maker, Panorama Factory and PanaVue, among others. This tutorial aims to improve understanding of most software stitching concepts by keeping the discussion as generic as possible, however actual software features may refer to a program called PTAssembler or PTGui (front-end for PanoTools or PTMender).
Generally speaking, fully customized stitching software will always achieve better quality than automated packages, but this may also result in being overly technical or time consuming. The biggest difference between options is in how they choose to address the tradeoff between automation and flexibility.
HUGIN PHOTO STITCHING SERIES
In order to begin processing our series of photos, we need to select an appropriate software program. Selection of perspective and projection typeĬomputer shifts, rotates and distorts photos to conform with requirements of stages 2 and 3 Selection of desired photo alignment and input of camera and lens specifications Equipment setup and acquisition of photographs
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