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New Years eve in Amsterdam by Jan van der Woning.

Tags for Panotools Projections

Panotools Projections

The most common Panotools projections are Equirectangular to make interactive 360x180 panoramas and Rectilinear to fix distortions of photos. But what about the others?
With a small Field of View (FoV) the difference isn't that obvious, but with a large Field of View things change quite a bit.

Imagine yourself standing in front of a large object and try to take a photo. Using a wide angle lens will get you visible distortions once you go above 50 degrees (100 degrees FoV) because of the Rectilinear projection.
Here is where the other projections come into place to map large Field of View objects to a print.

This is an example of an extreme Field of View, standing right in front a Ferris wheel taking several pictures using a 24mm lens:

There is no perfect print projection for this, but depending on the purpose, one of the Panotools projections supported by PTGui might do the trick. On the other hand, using an interactive panoramic viewer working off an Equirectangular projection will render a Rectilinear output in the viewer window. Close to perfect as possible, but not printable as one complete unit.

Here is a list of the projections and their appearance for extreme FoV:


Rectilinear

The projection of a standard camera lens and has progressive visible distortion for increasing Field of View.
Vertical and horizontal lines are preserved.

Cylindrical

The vertical projection is rectilinear and therefore has the same limitations as the Rectilinear projection for the vertical field of view. The horizontal projection is linear and perfectly suited for a 360 degree view. Nothing is distorted from left to right (horizontally), but from bottom to top (vertically).
Vertical lines and the center horizontal line are preserved.

Equirectangular

Similar to the Cylindric projection, but the vertical projection maps the 180 degrees FoV and is used for 360x180 (full sphere) panoramic images.
Vertical lines and the center horizontal line are preserved.

Circular

Fish eye projection

Fullframe

Fish eye projection with limited Field of View

Stereographic

Projection of a sphere to a plane. Angles are preserved, but distances and figures are distorted.

Mercator

Similar to the Cylindric projection, but with less vertical stretching.

Vedutismo

Diagonal lines through the center are preserved.

All Transverse projections are rotated 90 degrees and can map the vertical to a 360 degree Field of View.

Transverse Cylindrical

Transverse Equirectangular

Transverse Mercator

Transverse Vedutismo

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Re: Panotools Projections

Thanks Jürgen for posting this valuable info here.

Carlos Chegado

President > IVRPA.org - The International VR Photography Association

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Re: Panotools Projections

Thanks Carlos,
I have an interactive panorama of the picture to get another view of the scene:
http://panorama.cpicture.net/projections.html
Internally it works off an equirectangular projection, but this is not a requirement
as long as all picture data is present and a projection to Rectilinear exists which is used
by the viewer app.

Jürgen

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