Panorama Photography 1

While working on various locations, we were often asked by photography enthusiasts about panoramas - how do they work, how to shoot them, etc.
Trying to address these questions, my good friend and panorama expert, Lex Nowak (www.lexnowakphotography.com), wrote his comments on panoramic photography. He recently agreed that i reuse his postings on this blog.
Here is what Lex is saying in 1st part of his tutorial:

The world of panoramic images is fascinating, and with the advancement of digital photography and stitching software, is more accessible than ever. To achieve satisfactory results some technical knowledge and discipline is required. Photography principles like good composition, lighting, depth of field etc still apply.
I will focus in this article on modern panoramas obtained by taking a series of overlapping images with digital camera and stitched with the software. I don’t have experience with film rotational camera like Noblex, or Widelux, so I can’t comment on those.
For the sake of clarity I divide panoramas into two categories:

• Flat, rectangular panoramas – with the angle view typically exceeding 80 deg.

These panoramas can have different type of projection -rectilinear, cylindrical or mercator.

• Virtual Reality panoramas – fully interactive panoramic image allowing for panning 360 deg. These panoramas can be cylindrical – full 360 movement left to right and spherical – full 360deg movement left to right, as well as up and down.

In the series of articles I will write about flat, rectangular panoramas – I call them “classic” as opposed to new breed of VR interactive.

CLASSIC PANORAMA – ANGLE OF VIEW AND PROJECTION
The field of view of the human eye is approximately 140- to 160 degrees. Panoramic image emulates that effect and gives illusion of open views. Human vertical field of view is far more limited – approximately 90 deg. Typical wide angle zoom, on Nikon DX sensor, at 12mm will have field of view 89 deg. There is no actual limit on what field of view panorama should encompass, but the angle of view will impose the correct panorama projection. You can use different type of projections, however there will be only one that “looks just right”. In case of rectilinear panoramas the 100-110 angle will give nice, straight converging lines and natural look.

Single viewpoint panoramas – most panoramas are shot from single viewpoint, where the camera is rotated around lens’s nodal point. The camera is mostly kept level so the horizontal and vertical lines remain relatively straight. Tilting camera e.g. towards the sky will cause converging of vertical lines towards vanishing point, with horizontal line remaining straight. In my articles I will focus on single viewpoint panoramas. Good examples of high quality classic panoramas can be found here – http://www.arnaudfrichphoto.com/

Multiple viewpoints panoramas- (also called multi-perspective) – this panorama is obtained by taking pictures perpendicularly to the subject at different intervals (viewpoints), with desired overlaps of the images. Multiple viewpoints panoramas can’t be stitched easily with traditional stitching software and usually require tedious assembly work in the Photoshop. There is very little distortion in these type of panoramas.
You can view examples of multi-viewpoint panos by artist Michael Koller here – http://www.seamlesscity.com/
There are several types of panorama projections: rectilinear, cylindrical, mercator, equirectangular. The main variable that controls panorama projection is the angle of view.
Rectilinear projection – This projection type is what most ordinary wide angle lenses aim to produce, so this is perhaps the projection with which we are most familiar. Its primary disadvantage is that it can greatly exaggerate perspective as the angle of view increases, leading to objects appearing skewed at the edges of the frame – thus generally I don’t recommend it for angles greater than 110 degrees. As I mentioned earlier, this type of projection will give natural look we are accustomed – it is also one of my favourites.
Cylindrical projection -Is the standard type rendered by traditional panoramic film cameras with a swing lens. Cylindrical projections maintain more accurate relative sizes of objects than rectilinear projections, however this is done at the expense of rendering lines parallel to the viewer’s line of sight as being curved (even though these would otherwise appear straight).
Because of vertical stretching at the top and bottom, this type is not suitable for images with a very large vertical angle of view.
Generally cylindrical projection can be used with angles up to 160 degrees – anything over that will create unnaturally bowed lines. I use this type of projection if I have wider angle of view and can’t use rectilinear.
Mercator projection – Is most closely related to the cylindrical and equirectangular projection types; and represents a compromise between these two types, providing for less vertical stretching and a greater usable vertical angle of view than cylindrical, but with more line curvature. I use this type if the image looks better than in cylindrical mode.
Equirectangular projection – Can show the entire vertical and horizontal angle of view up to 360 degrees. This type maps the latitude and longitude coordinates of a spherical globe directly onto horizontal and vertical coordinates of a grid, where this grid is roughly twice as wide as it is tall. Horizontal stretching therefore increases further from the poles, with the north and south poles being stretched across the entire upper and lower edges of the flattened grid.