One feature of equirectangular images that stands out here is the multiple vanishing points. The railroad tracks run North and South. The vanishing point on the right side is North and the one on the left is South. The largest handcar is directly West and the extreme left and right edges of the image is East. You can visualize how the image works if you think of the center of the image wrapped around you and the top image shrunk down to the "straight up" point and the bottom edge shrunk down to the "straight down" point. Because you already know how railroad tracks work visually this image helps to see how equirectangular images work.

The fact that you see two handcars in this image is because this image is a composite of 4 separate photographs taken over the span of about 15 seconds. There is also two instances of the girl in the red shirt, near the right side, walking her little white dog. Below are the 4 fisheye frames before they are stitched into the equirectangular image.

I find that equirectangular images that don't have straight lines in the lower foreground like the handcar image are more visually pleasing. The railroad tracks are too much of a distraction because you attention keeps coming back to them trying to figure out why this image is so strange.

The Salmon Days image below looks more conventional because the foreground doesn't have any straight line that emphasize the fact there are two vanishing points.

About These Spherical Panoramas

The panoramas on this site are a form of spherical projection. Spherical projection is a way of viewing all directions at once. Seeing all directions at once is not a very intuitive concept. One very natural way of looking all directions at once is QuickTimeVR which is a web viewer that allows one to virtually float in the center of a photo-sphere and control which direction you look by dragging the cursor on the surface of the image. Click here to try it if you haven't already.

QuickTimeVR is great if you're only going to look at an image with a web browser. However, if you want something to hang on your wall QuickTimeVR won't do it! A form of image that can be printed and displayed, used in the process of creating QucktimeVR images, is called a equirectangular image. This is everything on the inside of a photo-sphere projected to a rectangle. The image below is a equirectangular image. It was used in the process of creating the QuickTimeVR image of the handcar demonstration.

The fisheye lens I use has a 179 degree vertical and horizontal field of view so the 4 fisheye images provide more than enough visual information needed to create a complete photo-sphere with about 50% overlap of the images.

Since the "straight-up" (zenith) direction and "straight-down" (nadir) of the photo-sphere is stretched to form the whole upper and lower edge of the equirectangular image, the upper and lower edge has the most distortion while the center (equator) of the image has no distortion. For this reason when printing a equirectangular image I crop much of the upper and lower edge resulting in an image as seen below.

In this image it is a little more difficult to notice the two vanishing points because the visual clues are the size of the people and not so much straight lines. Here the South vanishing point is directly in the center of the image and the North vanishing point is on the extreme right and left edge of the image.