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Lens: I purchased a 10.5 mm fisheye lens for my Nikon D50 camera. This lens was made for DSLR cameras. It is a full format lens, i.e. a field of view of 180° is only attained in the diagonal. The smaller side sees a bit over 80° and the wider one nearly 140°. First, I considered buying a Sigma 8 mm, a full frame round fisheye, to shoot skydome panoramas. I considered this mainly to save the money for a panorama head.

With the lens bought, I need eight pictures for a full spherical panorama. Six exposures in 60° horizontal intervals and one each for the zenith and the nadir. I found out, however, that I can save myself the trouble to take a nadir shot. It is easier to complete it by a bit of cheating than labour to retouch the panorama head out of the picture. So, that makes seven photographs. For an HDRI panorama, four to twelve exposures per step are needed which sums up to 28 to 84 photos.

Here the rational behind the idea of leaving out the nadir. On the left side, the nadir was photographed, not so at right. The upper part shows the panorama in equirectangular or spherical projection. These panoramas were mapped on a sphere in Bryce. In the centre of that sphere was the camera. Also within the sphere a rip-cage (free resource to be found in the raytracing department). The panorama head extends as far as 33° of the nadir's surface. Without the nadir photo, only 21° are missing (see red arrows or triangles), that can be completed using a graphics application.

Panorama Head: I decided to go for a Manfrotto MN-303 SPH spherical panorama head. Unfortunately, my tripod turned out to be too weak to carry this head and I had to replace it by a Manfrotto MA 190XPRO. Between the tripod and the panorama head, I added a MA-438 ball camera leveller. The latter comes in very handy to fine align the camera horizontally. The panorama head with the camera can be tilted by ±10° in all directions.

To the right, tripod, ball leveller, panorama head and camera while taking the «Claustro Pano». This panorama in a small and narrow room was made to check whether the camera is correctly adjusted to the nodal point of the lens. The nearest wall was 16 inches from the lens. In the resulting 8400 x 4200 pixel panorama, errors up to 4 pixels can be found. I consider this acceptable.

We have to add that a second serie with similar settings was stitched by PTGui to a perfect Claustro panorama. This was not possible with the original pictures from the first series.

Free: Hugin, a GUI for the Pano-Tools by Prof. Helmut Dersch, can only be recommended; download at http://hugin.sourceforge.net/. Hugin even stitches HDRI panoramas, however, only up to a certain size, depending on the amount of computer memory. Hugin creates the whole panorama in memory and if there is not enough of it, Hugin refuses to continue.

This problem can be circumvented. Sort the pictures in panoramas per exposure time and select the best exposure to stitch the panorama. Save the project and move it to another folder after Hugin was closed. Double-clicking on the project file will open Hugin but it does not find the pictures and prompts for the file names. Give it the pictures of the first exposure panorama. Hugin creates the panorama. Do the same for the panorama with the next exposure and repeat until all panoramas for each exposure are done. The panoramas can then be assembled into an HDRI using another program (the free HDRShop just about manages a 8400 x 4200 pixel panorama) and, if required, tone-mapped in yet another program. The free Picturenaut handles such files without any problems.

Currently, Hugin does not support multicore processors. However, you can launch as many instances of Hugin as your machine has cores or processors. My workhorse has got two cores and I can assemble two panoramas in parallel. Working with Hugin is a bit time-consuming but you can get professional quality results.

Commercial: The money spent for PTGui is well invested. Convince yourself by downloading a trial version: http://www.ptgui.com/. The professional version assembles spherical HDRI panoramas in one go. Time saving is huge. PTGui identifies the pictures loaded by their EXIF data and finds out if there are multiple exposures used for a single panorama. Also, setting the control points automatically works quite reliably.

I have worked with Hugin and PTGui and I can recommend both of them. If time is a scarce resource, consider purchasing PTGui. This program sets the control points in the original pictures and stitches picture after picture without using a lot of memory. A panorama with 7 pictures with 11 exposures each (77 photographs) are stitched to a spherical HDRI panorama almost fully automatic in about half an hour. The result is professional quality.

Cylindrical Panoramas: Both programs mentioned above can be used to stitch cylindrical panoramas as well. However, if you go for conventional cylindrical, non-HDRI, panoramas, a less expensive program will nicely do. For this, I can recommend PanoramaStudio http://www.tshsoft.de/index.html. It is about ten times faster to automatically stitch a panorama than the more expensive Realviz stitcher and the result is flawless, something I cannot say from the Realviz stitcher. This should not be considered a promotion for the products mentioned, there are more panorama programs on the market which I do not know and have no experience with. I purchased the applications mentioned and worked with them. Starting with version 1.6, PanoramaStudio can also create panoramas from 16-bit RAW images.

The Nadir Challenge one more time. If non-HDRI panoramas are made, the nadir picture can be shot freehand and added later on manually. Using multiple exposed photographs for a HDRI panorama, you can forget that. The exposures never fit precisely! There are two ways to go.

Copy parts of the picture from nearby the nadir with soft edges into the black «hole». Starting with Photoshop CS2 this is also possible for HDRI, CS3 extended works considerably faster.
Placing a mirror ball or a logo at the place of the black spot.

In the first case the nadir is needed undistorted, which is not the case in the spherical projection. In this projection, it is exceedingly difficult to get an acceptable result. Many methods can be found on the Internet, all of them rather elaborate and complicated in my view. I have a better — in my view — method to offer. No matter whether you have an HDRI or a conventional panorama, the free HDRShop handles this with two clicks.

Open the spherical panorama in HDRShop and in the Panoramic Transformation dialogue, select for input and output projection Latitude/Longitude (spherical). For 3D Rotation select Arbitrary Rotation and enter 90.0000 for X. The result is tilted. Now, in the Transform drop down select the option Shift w/wrap… and enter in the field Right the height of the panorama (height is half the width). Now, the nadir is in the centre. Save the picture with a new name, then complete the nadir.

At left, the well known Claustro-Panorama without the nadir shot. At right, the nadir almost undistorted in the centre after tilting and shifting the panorama in HDRShop.

When the nadir is complete, save the file and open it again in HDRShop. Do the same in the same order as before: Arbitrary Rotation X = 90.0000, then shift with wrap right by half the width, save and done.

In the second case everything is yet simpler. Open the spherical panorama in HDRShop and select from the Transform drop down the option Flip Vertical . Save the result with a new name. Open the original and the flipped panorama in a graphics application (e.g. Photoshop). Measure the maximal height of the black nadir. Copy the non-black part from the flipped panorama and resize its height (but not the width) to the size of the black spot's (actually the black strip's) height. Copy the asymetrical scaled image into the original panorama and place it at the lower edge. That's it.

At left, the well known claustro-panorama without the nadir shot. At upper right, the flipped and resized part, below at left that part copied into the panorama and at lower right the view from top onto the inserted mirror ball.

In the main topic Raytracing , the chapter HDRShop? contains an elaborate and quite complete tutorial about HDRShop.

HDRI photographs do not go along well with animated objects. The wind shakes the trees, clouds wander in the sky, the sun, too, by 15° per hour and the shadows follow. Acquiring an HDRI panorama is literally a race against time. You should not need more than 20 minutes to get 28 to 84 photographs into the camera — sun and shadows wander a distance of 5° in that time even without wind.

After a couple of field tests with mediocre results and later with acceptable ones, I decided to follow these steps. First I find a place for the tripod which can easily added later on by a bit of cheating, examples are meadow, sree, and that kind. Then, I align the camera so it is horizontal in any direction (azimuth). Then I point it so that the brightest light (the sun if outdoors) is horizontal in the centre of the picture. This is azimuth 0. I move the camera around and check whether there are good points that will be common in two adjacent pictures. If the sun is out, the lens is set to the smallest aperture (highest f-stop) and the shortest exposure time will be the fastes shutter speed available. Then, I look for the darkest part and determine the exposure time or shutter speed to get that also with some brightness.

Back to azimuth 0, I tilt the camera straight up at the zenith (90°) and start the series of exposures. When done, the camera gets back horizontal and a new series of exposures is taken from the same azimuth (0). Then, the camera is turned to the right by a step (the width of the steps in degrees can be set on the Manfrotto head and it locks in place; 60° in my case). Third series of exposures, rotate to next step, and so on until the camera is back at 0.

There is enough time to exchange a full memory card by an empty one. But there is not enough time to replace a depleted battery by a fully charged one. The camera must be removed from the panorama head and maybe the rail on the camera has to be removed to get access to the battery compartment. After the battery has been changed, the camera won't be aligned at one pixel accuracy on the tripod. In such a case, start the whole process anew. The series of photographs can never be properly aligned to an HDRI panorama.

There are enough water balances on the tripod. Nevertheless, I put another one at the contact for an external flashlight. Not to check whether the camera is indeed aligned horizontal, rather to see when the camera has finished wobbling after the next exposition time was set. The balance is accurate enough to even register the movement of the camera after the mirror flipped up and down. The shutter is triggered by a remote control.