Difference between revisions of "The why and how of panoramas"
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--[[User:Roger|Roger]] 18:03, 9 Mar 2005 (EST)
--[[User:Roger|Roger]] 18:03, 9 Mar 2005 (EST)
Revision as of 16:25, 12 November 2005
The Why and How of Panoramas
An article originally written for members of the Usefilm.com photographic community.
I love panoramas. They're what brought me back into photography after a lapse of many years. But it's clearly a minority taste. Here, I'd like to share some of the attractions of panorama photography, introduce available options in equipment and techniques, and hopefully encourage others to try this fascinating, challenging and ultimately rewarding format.
First, just what IS a panorama? Most people regard it as a format where the width of the picture is typically at least two or three times the height, whatever the angular coverage.?Some would limit it to the very wide-angle panoramas you can get with swing-lens or rotary cameras, anything from 120 degrees to 360 degrees horizontally. It obviously includes photos giving similar angular coverage but stitched from several--sometimes many--individual photographs. Me? I'll take any or all of those definitions. To me, they are all panoramas, and all can produce visually arresting, satisfying images. Some, of course, are taken specifically for viewing as scrollable panoramas via the Internet and are not intended for viewing as prints. It was the desire to take so-called�virtual reality�(VR) photographs of this kind for the web that started me off down the panorama road.
The easiest way to take panoramas is with a disposable panorama camera. At their widest, these have plastic lenses with focal lengths of 15 to 17mm. That's very wide--a 17mm lens will have a horizontal coverage of well over 90 degrees and a 15mm lens one of over 100 degrees! They produce the panorama format by masking off the top and bottom of the standard 24 x 36mm 135 format negative. If the aspect ratio is 2.5:1, the width of the image is 36mm and the height a little less than 15mm. APS cameras produce panoramas from even smaller areas of film. There are people in usefilm.com who can enjoy using the Holga, so it's not strange that there are those who enjoy taking panoramas with this simple equipment, even if they can't make wall-sized prints from them. But of course, if you have a reasonably wide lens on your camera, say at least 25mm or preferably 21mm for the 135 format, you can crop to the panorama format. Here is an example of a panorama made this way, http://www.pgallery.net/rogerama/image-38597.html.
For me, the fun of photography is mostly in being able to capture the scene that caught my eye so that I can share it with others, and panoramas do this in a way that looks to me more natural, more the way it�really�looked. Our eyes have a very wide field of view, and a good panorama can create something of the overall�look�of the scene as it appears to us. I suppose this goes along with my preference for wide-angle lenses and the fact that I seldom reach for a telephoto. I'm more likely to want to�get everything in�than to zoom in on a tiny part of the scene. There's also a much less widely recognized feature of panoramas: they often have an almost stereoscopic sense of depth to them, particularly if there is a larger object in the foreground to establish the perspective. Those old enough to remember the introduction of the Cinerama format to movie theaters may recall that the advertising talked about the greatly enhanced sense of immediacy. This arises from the �wrap around� effect that mimics our normal vision, giving an illusion of depth and a greater sense of involvement in the action. There's something of that in the simple still panorama. There's even more of it in virtual reality panoramas on the web. If you have a fast Internet connection, here is a site that will astonish you with its beautiful interactive panoramas! http://www.panoramas.dk/index.html. You'll need the Quicktime plug-in.
If the simplest and easiest way to take panoramas is with a disposable camera, the ultimate camera--appealing to the professional and the advanced amateur alike--may be the bulky Fuji 6 x 17, taking transparencies that measure all of 6 x 17cm on 120/220 film. This has interchangeable lenses, the most popular of which is the 90cm Fujinon. Visit www.fujirangefinder.com and note how many magnificent panoramas are taken with this camera!
A good compromise between the Fuji 6 x 17 and trying to cram an entire panorama on a cut-down standard 135 format image is the Hasselblad Xpan. The Xpan I and its recent successor the Xpan II, made under an OEM contract by Fuji in Japan and sold there as the Fuji TX-1 and 2, use standard 35mm film but produces images almost 7cm wide, 21 of them on a standard 36-exposure cassette. This means that the standard 45mm F/4 lens gives the equivalent horizontal angular coverage of a 25mm lens in the standard 135 format. This doesn't seem very wide for a panorama, but because the perspective of images created by a 45mm lens is very close to the ideal 43mm (�ideal� because this focal length equals the diagonal of the standard 24 x 36mm format), and because the spatial distortion resulting from rectilinear lens design is not too obvious at this horizontal angular coverage, the images look very natural. This is currently my favorite camera. Here is an example that shows the natural perspective given by this format; http://www.pgallery.net/rogerama/image-47011.html.
Another way of obtaining a larger negative from standard 35mm film is to use an adaptor with a medium format camera. The Mamiya 7 II, normally taking 6 x 7 format photographs on 120/220 film, can be used in this way to give negatives (or transparencies, of course) the same size as the Hasselblad Xpan.
You may ask �Why bother with special adaptors, when you can take the same width photographs on 120/220 film and crop away the unwanted areas from the top and bottoms of the image?� This is a good question, and this option has the advantage of being able to choose exactly where the panoramic image shall come inside the full vertical height of the negative. This means you get some of the advantages of a perspective control lens with a �shift� adjustment. For example, by selecting the very top of the 6 x 7 image, you can often squeeze in the tops of buildings and reduce the area taken up by the large open foregrounds that wide-angle lenses tend to give. The reason for using 35mm film adaptors, though, is the much greater variety and availability of 35mm film.
Yet another approach is to use a swing-lens camera. Examples include my old faithful, the Japanese-built Widelux (now out of production). This gives a full 130-degrees horizontal coverage by sweeping the lens through an arc while the focal plane slit follows it across the length of the image on the film. Winding on the film winds up the clockwork that drives the lens. The film is kept not flat, but in a curved plane centering on the nodal point (the optical center, if you like) of the lens. The Russian Horizon (there is also an earlier version confusingly called the Horizont; both operate on exactly the same principle) is still being manufactured, and if you buy from a reputable dealer who will replace or repair under warranty cameras with manufacturing defects, which unfortunately are common, it can be a very cost-effective choice and gives excellent results. Probably the most widely used swing-lens camera is the Noblex, produced in the former East Germany. This is not one but a whole family of swing-lens cameras, from 135 format to 120/220 and covering different angular ranges. They use an electric motor rather than clockwork to drive the lens. This has the advantage of accurate speed control but is rather heavy on batteries. Some models offer a centimeter of so of vertical shift (useful for the reasons described above) and an optional exposure-control accessory that alters the exposure as the lens swings round. When you think of it, this is a very desirable feature, as the optimum exposure from the same vantage point but pointing in two directions 120 degrees apart may be quite different. I would be interested to know how the digital cameras that offer stitching programs to create panoramas from a series of individual shots handle this problem. There is also a Chinese swing-lens camera for the 120/220 format, but opinions are divided on whether this a serious contender. One advantage of swing-lens cameras is that only light passing through the central portion of the lens is used, which reduces the effects of lens aberrations/distortions and gives high quality images even without the most expensive lenses. Here is a shot of mine that illustrates the problem of varying lighting over a wide range of �sweep.� http://www.pgallery.net/rogerama/image-27155.html. The version of this in my Usefilm.com portfolio has had the darker areas at both ends of the image cropped away. http://www.usefilm.com/image/258119.html.
Finally, we come to cameras designed to swing through the entire 360 degrees, taking an all-round panorama (ideal for web-based VR displays) in a single shot. There is a surprisingly wide variety of these. You can go for a wooden one, hand made to order by Alan Zinn in your choice of woods, that you swing around manually, relying on the flywheel effect to keep lens motion constant. This uses either standard perforated 35mm film or--if you wish--it can use the rather restricted range of unperforated film to give a deeper vertical image (http://panoramacamera.us/ ). Or there is the much more sophisticated �Voyageur� hand made by Gildas le Lostec in France that comes with radio remote control (so that you can get out of the field of view and still fire your shot at the critical moment). Visit http://perso.wanadoo.fr/panorama to see Gildas' camera and some sensational panoramas in his gallery. And at the top end of the range are the Swiss �Round Shot,� high-precision cameras for the professional or the wealthy amateur. There are others too numerous to mention in a brief survey like this. However, since there are so many digital camera enthusiasts on usefilm.com, and my own account is necessarily biased towards my own preferences for film, I should mention that there is at least one rotary lens camera that is entirely digital. The sensor, instead of being an area, is a line, and the line essentially scans the entire image like the slit of the focal plane shutter in the film-based swing lens cameras. The system requires a notebook computer to control it, and is expensive. But the results are impressive. If you have a very fast Internet connection, you may like to check it out. http://epan.net. (The quoted price was a cool US$25,000! and I see that the camera has now been discontinued.)
Finally, we come to the stitching of individual images, taken pointing in different directions, into a single, smooth panorama. Some digital cameras come with the software to make this fairly straightforward (it can be a major hassle using PhotoShop or other graphic program), but they have the compensating disadvantage that digital cameras don't usually have very wide angle lenses. The wider the angle of coverage, the fewer shots it takes you to square the circle, and the less stitching you have to do. That's a major consideration. There are several software packages, from freeware to shareware to full commercial software OTC packages that charge you both for the original program and for every individual panorama you make with it. I've done quite a bit of stitching, and it does get rather wearisome. At the moment I'm using a 16mm full-frame fisheye lens on a 35mm camera to take just four shots, one for each of the four points of the compass, and stitch those into a 360-degree panorama. This is in "landscape" orientation. You'd get a deeper image, but have to take more shots, if the camera were used in "portrait" orientation. I have seen wonderful examples of how well this can work but don't have a URL for you.
Finally, I'd like to give some hints on taking panoramas. If I do so, this is not to say I always avoid mistakes. I've learned about most of the possible mistakes by making them... and I'm still trying to learn how to avoid them.
The first thing to note is that the camera must be completely level. This is true whichever kind of camera you use. But the most visually disturbing results occur when swing-lens or rotating cameras are not strictly horizontal: the horizon rears up or swoops down in a must disconcerting way! Definitely to be avoided. Here's a typical example; http://www.pgallery.net/rogerama/image-50843.html. If you are stitching, it is better not to take hand-held shots if at all possible. If you do, you may rotate or tilt the camera slightly from one shot to the next, and this is often difficult and sometimes impossible to compensate for. Better to use a panoramic head on your tripod, preferably one specially designed for the purpose and with built-in bubble level indicators. Remember that even if you set the camera level on the tripod, it may not remain level as you swing around. You should check the level with the camera pointing in two different directions at right angles. Another thing to watch when you are stitching photos, is that you need a fairly generous area of overlap. This is because the edges of different shots have to be �warped� to conform with each other, and if the overlap is inadequate, this may not be possible. A good rule of thumb is that each shot should overlap with at least one third of the next shot. Some recommend a 50% overlap. This is another argument for using a fairly wide-angle lens, although lenses much shorter than 25mm (135 format) are subject to higher spatial distortion and require much more warping to conform. So far, I have found 21mm or 25mm to be a good compromise, and 15mm less successful.
Probably the least understood but most important of the errors you can make taking shots for stitching is to rotate the camera about a point that is not on the optical center of the lens, the so-called�nodal�point. The easiest way to understand this is to imagine your camera is pointing directly along a fence stretching away from you, with the far end hidden by the near end. As you swing the camera to point to the left and right of the fence, if you are rotating it about the nodal point, neither side of the fence will appear in your image, even when it occupies the edge of the image: the fence will still stretch away in a straight line. It's easy enough to check this with a single-lens reflex or a digital camera with an LCD image. Mount the camera on your tripod, rotate the camera, and move it backwards and forward on the tripod platform until, when you rotate it, two poles at different distances from you remain perfectly aligned, the one hidden by the other. Even a millimeter of camera displacement will make a big difference. Why is this so important? For two images to blend together in the area where they overlap, there must be no parallax between objects in the overlapping region. If there is parallax, there is no way a stitching program can combine them. (This adjustment is easy with SLRs, but for lovers of rangefinder cameras like me, it is far from easy. I won't bore you with the details of all that is involved!)
One final problem of stitching panoramas is not really anything to do with cameras or techniques. It's the problem of doppelgangers. This German word is, I am told, used for ghostly�doubles.�In stitched panoramas it refers to people who have moved within the area of overlap between two shots. There is obviously going to be a time lag between when the two shots are taken, and if one or more people move before the second shot is taken, they will appear in slightly different positions on the two images. The result will be TWO shadowy images, with the backgrounds showing through them. Ghostly and rather off-putting! Some stitching programs know how to cope with this phenomenon, but even then they have varied success in dealing with it. Often, it takes some fancy work with PhotoShop or the graphic program of your choice to eliminate this troubling effect. (There are some�ghosts�of this kind in one of my panoramas listed in this article, if you look in the right places.) In effect, stitching is not very useful for crowd scenes where there's a lot of movement. I wouldn't want to have to stitch eight or ten photos of the Boston Marathon, for instance!
One final issue you may want to be aware of is the difference between fixed lens and swing-lens panorama cameras. The TX-1 that I use has a very expensive option in the form of a 30mm lens. This gives the same horizontal coverage as a 17mm lens in 135 format, but even so, at a little over 90 degrees, this is considerably less than the 120 degrees a Horizon will give you at a small fraction of the cost. But cost is not the only factor affecting the choice of fixed vs. swing-lens panorama cameras. To get the wide-angle coverage with a fixed lens, rectilinear design is used. This keeps straight the lines that were straight in the subject being photographed. Unfortunately, as you may have noticed if you look at people in the corners of shots taken with very wide-angle lenses, they are subject to spatial distortion that causes heads to become elongated or foreshortened depending on which way people are facing. Swing-lens shots, on the other hand, are not subject to spatial distortion but convert straight lines in buildings or streets into curves. This can be just as unsettling as those people with elongated heads. With experience, and the careful choice of the angle at which to take the subject, it is possible to make this effect less obvious, but it cannot be entirely avoided. For instance, it's not too obvious in http://www.usefilm.com/image/225427.html. My simple rule is,�swing-lens for people�(and when the widest angle coverage is essential,��fixed lens for architecture and cityscapes.�In this way, my old Widelux to some extent compensates for the fact I cannot justify the purchase of the wider-angle 30mm lens for my TX-1.
I do hope that some readers will attempt a few panoramic shots, and will enjoy the experience. The rigid 800-pixel limit on image size at usefilm.com may lead you to find another Internet home for your images, though. One final word; don't forget that you can turn panorama cameras on their side and use them in�portrait�mode. Great for giraffes, if nothing else! (See http://www.usefilm.com/image/227996.html )
--Roger 18:03, 9 Mar 2005 (EST)