Something great has happened in photographic imaging recently and it has gone almost unnoticed in many quarters. The new ability to seamlessly stitch together a number of images has produced a new and exciting creative device for photographers with a bit of digital savvy. We look at how it is done, what to avoid and some of the little tricks that we have learned along the way.
stitching? you mean just joining, right?
It has always been possible to stick two pictures end to end and thus generate the effect of a panorama sweep. The problem with this approach is that it ignores the physics of photography and therefore makes it difficult, if not impossible, to join pictures without miss-match. This is because cameras take flat pictures and as you rotate the camera all you end up with is a group of images that are tangents to a circle rather than part of it. Stitching software overcomes this problem by “curving” the image segments before joining them.
is it perfect?
No, stitching is not perfect, but it is often so good that no one will notice the joins especially if the ingredient images are well shot.
Panorama, 2D panorama, 360 degrees and QuickTime VR
There is a lot of software on the market but for the sake of simplicity we selected three representative programs to explore the possibilities.
Perhaps the easiest to use is QuickStitch from Enroute Imaging. It can produce both horizontal and vertical sweep panoramas, and also 2 dimensional panoramas that include segments shot both vertically and horizontally. QuickStitch’s ability to create panoramas in 2D makes it very attractive, and is not shared by most applications on the market.
An unfortunate aspect of QuickStitch’s simplicity is a lack of controls. There is no provision for manually adjusting segment alignment and for this reason, it’s usually passed over by professional image makers.
Live Picture PhotoVista
Live Picture PhotoVista can create both panoramas and 360 degree sweeps suitable for QuickTime VR, is very easy to use and has some intelligent programming behind its simple facade. For instance PhotoVista has the lowest RAM requirements of all the software we tested, was the most robust and bug free, and has the ability to guess camera angle of view.
More complex than PhotoVista and less intuitive, is Nodester software from Roundabout Logic, which is designed specifically for the production of professional quality QuickTime VR movies but is also very capable of producing panorama images as end products. Nodester has a well written 107 page manual that comes in paper and digital PDF versions.
There’s also lots of subtle control over blending adjacent images, and slightly larger preview images in what it calls the Correlate Panel, where joining is controlled. Though these programs offer auto alignment, it is often necessary to micro adjust segment positioning, so the bigger the previews, the easier it is. Due to a legal stouch, Nodester is no longer available, but many of its features can be found in the soon to be released VR Worx from VR Toolbox, Inc.
steps in shooting panoramas
1. Determine the optimum exposure by measuring at the most important part of the sweep. Large sweeps usually contain areas of over and / or under exposure, so concentrate on getting the values correct where it counts.
2. Begin at 0 degrees on your pano rig.
3. Level the tripod as well as possible, then adjust the head so that the camera is held in a horizontal position. Then make micro adjustments using a spirit level. The whole idea of this step is to eliminate asymmetrical tilt angles. If you are working without a tripod you’ll just have to wing it. Some professional cameras offer accessory through-the-lens viewing screens with a grid pattern, which are just the shot for this kind of work, making it easy to get perfect horizontal and vertical alignment. In stitched results where image edges don’t match well you will see typical blurry areas, so it is worth getting alignment as close to perfect as possible. If you’re hand holding the camera, it is difficult to maintain all images at exactly horizontal and an image that is not in an exact plane with the others will not match.
4. Most programs need 50% overlap. More may be OK but less can cause misalignment and banding problems. The best antidote is to use as wide a lens
( or equivalent setting on a zoom lens ) as possible. Wide lenses make overlap errors smaller.
Many recommend vertical orientation of the camera for the widest Field Of View (FOV) particularly for QuickTime VR where a feeling of immersion for the viewer may be desirable, but horizontal is still OK. You will probably find it easier to shoot horizontal and it means less stitching too.
With a zoom lens you must, of course, use the same focal length setting for all the images in a sequence, or they won’t stitch properly.
You may need to add extra lighting for indoor scenes which have unacceptably dark areas, or some very bright areas which necessitates lifting the darker areas. An alternative is to shoot at another time of day or night when lighting ratios are more amenable. The lighting is most even around noon, but it can also be the most boring at that time. Traditionally landscape photographers shoot near sunset or early in the morning because the light is most interesting then, but it can also be problematical as well, producing lens flares, deep shadows and uneven lighting. It’s a trade-off.
The closer you are to your subject matter, the more important it is to have the camera pivoting on the camera lens nodal point. The nodal point is where light rays cross over inside the lens. You can guess this as half way between the front lens element and the focal plane when the lens is focused on infinity. Rotating around the cameras nodal point eliminates parallax error.
If you’re doing a 360 degree stitch, the most crucial join will be between the first and last frames. Where possible, pick the most amorphous part of the vista, such as a blank wall, for these frames, so that any miss-match due to misalignment is not so obvious.
Have a well thought out game plan ( plan of attack). It’s easy to forget whether you have shot a particular frame for example, so approach the work in an orderly structured way avoiding any distraction. No day dreaming. I only mention this because it’s my biggest problem.
I usually shoot the full sweep twice so that there is always a spare frame if something goes wrong. This is especially important if the camera is handheld because exact vertical and horizontal alignment is very difficult.
Nowadays most tripod heads feature a disk at the base displaying the degrees of rotation, which is necessary for accurate rotation measurement. This and the availability of a good 2-way spirit level are the two most important pieces of equipment.
the Olympus solution
Olympus has built a very useful panorama solution into its cameras and “p” memory smart cards. Olympus software supplied with their cameras uses information stored with the images in the smart card to cue panorama production. Files can of course, also be used with other stitching software. Interestingly, Olympus work on a mere 20% image overlap. A big advantage of using the Olympus solution is that exposure is held constant through the full set of a panorama sequence, which is impossible to achieve with most other
consumer digital cameras.
Just a little aesthetic note: One of the great advantages of a sweeping panorama is the opportunity to include a wide variety of picture information and it’s easy to get carried away and include as much as possible. Sometimes it’s better to keep the image and hence the story, simpler, by omitting distracting elements and concentrating on the important ones. One way to accomplish this is by moving closer to the main point of interest so that it dominates the picture. In photography one always has to be aware of these matters but they become more important in a very wide picture.
Objects that move, such as ships, cars and people, can be a real headache in panorama stitching. Where possible shoot the object destination first and then the object. Otherwise you are likely to get two or three images of the object in the sweep. This is a useful compositional device (see the emus image) but can also be an annoying problem.
camera options: film + scan
Shooting film and then scanning offers a number of advantages, the principal being resolution. As much as we love digital cameras, it has to be admitted that a good scan from even a cheap 35 mm camera shot is going to give better resolution and definition than you’ll get from all but the most expensive digital cameras. We are all familiar with film. It is ubiquitous, comes in lots of speeds, and it provides a separate analogue record of the event for further use. Conventional film cameras also offer a large choice of lenses. Wide and super wide angle lenses which are ideal for panorama production are unavailable for consumer digital cameras, so if you need these stick to film cameras. Filters such as Polarising filters are more easily attached to conventional cameras since the lenses on many consumer digital cameras are unthreaded.
On the downside, film has to be purchased, processed and scanned and all this means lots of costs in money and time. Hours can be spent doing what a digicam can do in moments.
Digital cameras produce an instant digital file, with maybe fewer artefacts, offer instant proofing by viewing the LCD screen on the back of the camera. Making panoramas multiplies the requirements for file acquisition and storage. Large capacity smart cards, Compact Flash cards and PCMCIA devices, and speedy download are required for efficient production. Being able to download in the field can also be useful.
need special hardware?
Apart from what we have mentioned so far, nothing else is actually necessary, but there are a few items that may be useful if your budget allows. There are several “pano” tripod heads on the market which make life easier for someone doing lots of this work but also cost hundreds of dollars and more. The two main features offered are click stop rotation and provision for shooting with the camera on a vertical axis. Click stops are handy but not necessary provided that you have a tripod head with degrees of rotation marked on it and most do nowadays. Like all photographers, we love gadgets but while a precision instrument for turning a camera on its side is attractive, we found that twenty minutes spent in the shed, bending a piece of flat metal and drilling holes in it where required, produced an L-bracket that performed flawlessly and for only a few dollars cost. Bear in mind also that there are situations when the camera can only be hand held.