Bit by Bit: Pulling Your Panorama Together with QuickTime
Gearing up to create panoramic photographs can be costly or inexpensive. At the costly end of the spectrum, conventional film and digital solutions by companies such as Charles Hulcher Co., Panoscan, and Seitz Phototechnik AG rotate under the power of a motor to capture panoramas, but costs begin at a few thousand for film models and about $12,000 for digital offerings. Fortunately, you can get results just as good with inexpensive camera equipment and with software that intelligently "stitches" multiple images into one continuous panorama.
In my previous column on panoramic photography, I wrote about the hardware required for producing high-quality panoramas with inexpensive cameras -- most notably, a panoramic camera mount that you can make yourself. This time around I'll focus on the stitching software used to create panoramas, and I'll share some tips that should help you move relatively smoothly into panoramic photography.
Stitched QuickTime panoramas are made with conventional cameras, conventional tripods, and special panoramic camera mounts that hold the camera vertically during a series of stepped exposures. You make a series of exposures, turning the camera a prescribed amount between frames. There must always be an overlap between the images, as the software that puts images together into a complete panorama needs two ends to compare before building the blended image of any two frames.
Many people have tried to paste photos together manually to make panoramas. In some circles it's considered an art form. But the problems of distortion and image perspective pose terrific challenges with this approach to panoramic imaging. Images pasted side-by-side will never line-up perfectly, and even minor differences in exposure will create visible seams.
Cut-and-paste panoramas suffer from problems of fit, exposure, and distortion.
Much of the blame for why manual stitching doesn't work rests with the optical capabilities of camera lenses. Normal-to-wide-angle lenses all have a certain amount of distortion. This distortion is a part of the optical properties of the lens, and is considered normal. When we look at an individual photo, we are usually unaware of the distortion, but it is there.
Barrel distortion in a wide angle lens causes the image to be distorted approximately along the lines in this grid.
Typical distortion in a wide angle photo is called barrel distortion. It tends to make an image shaped like an inverse barrel. When we try pasting individual images together, this distortion is the single greatest cause of trouble. Images spread away from the center, and this makes the edges difficult or impossible to join together. Cut-and-paste works much better with photos taken with telephoto lenses, but long lenses don't gather the up-close subject matter we usually want to record in a panoramic image.
When several images are pasted next to one another, the effect of barrel distortion becomes noticeable. The images won't fit next to one another. Panoramic stitching software removes the barrel distortion prior to stitching pairs of images together.
Panoramic stitching programs reverse the barrel-distortion effect, then assemble pairs of images by finding common points in adjacent images. It then blends the edges together to remove any visible seams, thus creating a cohesive panoramic photo.
From an end-user standpoint, the process is a breeze with just about any present-day stitching solution: You line up the images you have taken in order -- left to right or right to left -- and then you either let the software stitch automatically, or you give it a hint here and there about the association of adjacent frames. Different solutions yield different results, however, and some offerings place artificial limits on image size, which can be a real problem if you're creating panoramas for print.
Stitching software overlaps the images, finds common points, and then aligns the image pairs together.
Though available for Macintosh only, QuickTime VR Authoring Studio is the absolute best stitching software I have found among the several I've tried both for the Macintosh and PC. Of the others I've tried, most either provided no preview, or the images were so small that I could barely identify them. A competitive product for both the Mac and PC -- VR Worx, from VR Toolbox -- has a good reputation as a serious QuickTime VR Authoring Studio competitor, but I have not had the pleasure of testing it. I have seen panoramas made with this software, however, and they look very good.
Both QuickTimeVR Authoring Studio and VR Worx yield professional-quality results, and both command a hefty price -- $395 for QTVR Authoring Studio and $299 for VR Worx. If you simply want to stitch together quickie panoramas to share with family and friends, you may be able to get away with any of a number of less-expensive solutions. For instance, MGI sells its $49.95 Photovista for both Macs and PCs, ArcSoft sells its Panorama Maker 2000 for both platforms for $29.95, and the Home edition of PixAround.com's PixMaker (PC only) can be had for a mere $19.95. With any non-professional solutions, however, be ready for some limitations: Some solutions restrict images size to only several megabytes, for example; I routinely make 50MB to 80MB panoramas. Some inexpensive solutions also just don't handle the stitching process as well as their pricier, pro-quality cousins. I continue to use the Apple QuickTIme VR Authoring Studio and am quite happy with it, though no upgrade has been offered for years.
Apple Computer's QuickTime VR Authoring Studio features a good interface, excellent tools for stitching, and a separate window for adjusting images for manual fit when the program fails to find the correct common points between images.
Apple's software is uncanny in its ability to find the common points between images, even if the camera wasn't level during exposure. The result is almost always satisfactory. Occasionally I have stumped it, though. On one image of the Golden Gate Bridge, the software couldn't differentiate between the many vertical cables that support the bridge. The software got slightly confused and stitched two of the photos incorrectly.
QuickTime VR Authoring Studio features a separate window for the manual adjustment of pairs of images, for when the software doesn't stitch images correctly on its own. You drag the image on the right over the image on the left until the positioning is correct.
Fortunately there is a separate window for giving positioning hints to the program. This frame-alignment window puts an image on the screen, and a transparent view of the adjacent image. You drag the transparent image atop its partner image to the correct position, click on the Zero button, then proceed. After I aligned the frames manually, the Golden Gate appeared perfectly stitched.
When the stitching process is complete, the software will make a single panoramic image, and will optionally make a navigable image in QTVR format -- an image viewers can pan about by moving their mouse. Creating the QTVR version is easy, and people love these images. I have made quite a few heads turn when showing them. They are most appropriate for the Web, and for making audiences suffer from vertigo in a darkened seminar room.
Four of 12 images in a 360-degree panoramic image. When photographed correctly, they all share the same exposure and focus, and there is an overlap between images.
Shooting a Stitched Panorama
Good stitching software can work minor miracles when joining images, but to get great results, you'll need to put care into capturing the images to begin with. Referring to a short checklist can be very helpful in the field, especially if things are happening quickly. I based the bolded items below on my own checklist, though I've added additional information here that may be helpful.
- Got film? Or, in the case of digital cameras, do you have enough memory space? I use color negative film in my regular camera when I shoot panoramas. Negative film is superior to transparency film for this purpose as it has greater exposure latitude and can tolerate significant overexposure. When making a panoramic image, you will nearly always get some overexposure since at one point you'll be facing the sun (also see exposure, below).
- Level mount. The rotational mount must be level. The best approach to leveling a camera for panoramic photography is to mount the bracket on a high quality ball-leveling mount. I use a Kaiser Phototechnik ball mount under my panoramic head, and it reduces my leveling time to about five seconds. This is a tremendous improvement over my early efforts at leveling the head by raising and lowering the tripod legs. Once the panoramic head is leveled, I always check to ensure that the camera is level on the mount. I carry a cut-off carpenter's level to measure the front plane of the lens (where a filter would attach). From here I am guaranteed an easy stitching process.
- Clean the lens. This really matters, as dust tends to repeat 16 times in a panorama. Clean your lens in advance of shooting, so you don't have to do it on a skyscraper roof in a 30-knot wind. My recommendation for lens cleaning is the Microstar lens-cleaning cloth. Available at most any camera store, they are the absolute best for cleaning optics. Clean the lens before setting the camera up for a series of shots.
- Set exposure. Manual exposure settings yield the best results. Before setting exposure, set up your tripod, and get your leveling out of the way. My method for determining correct exposure is to face the sun, then point straight out with my right arm. I then face the camera that way, and set the exposure in this direction, 90 degrees off the sun. Then I lock the camera on that exposure. With negative films this seems to work fine. When facing the sun, the image will be overexposed, and all the other steps will be acceptably exposed. The overexposure latitude of negative films will still allow for detail in the images shot into the sun.
- Set focus. The best images are made with focus locked at infinity or on the subject, if it is closer than infinity. Most panoramas are focused on infinity. Even most point-and-shoot cameras allow infinity lock. I recommend this, as you definitely don't want the individual images to be focused on different distances, which makes high-quality stitching difficult at best. If you are making an indoor panorama, focus on the subject, and lock the focus if possible.
- Cover the viewfinder on an SLR camera. If you're making a panoramic image with a single-lens-reflex camera, cover the viewfinder during the exposure series. It is surprising how much light can infiltrate the camera through the viewfinder. Some professional cameras have a shutter that can be closed to block the viewfinder. If your camera does not, place your hand over the viewfinder while making the exposures, or put your eye up to the viewfinder.
It seems like a lot to remember, but a successful panoramic image is much more complex than a single image, and if only one frame is bad in a rotation, it will ruin the entire image.
After shooting the panorama, process the film and scan it, or with a digital camera, copy the files to your computer for stitching. For scanning I am a big advocate of Kodak Photo CD discs. No process is simpler or more precise at the price. I have not tried the PC Photo discs now offered by Kodak, but they are probably good, too (though maybe a bit low in resolution).
Retouching and Adjusting
Panoramic images are like regular photos -- only longer. You will probably need to examine the image carefully and do a little cloning to remove dust spots and other minor problems.
This image of Humayun's Tomb in New Delhi, India, was taken with a 17mm lens on a Nikon D1 professional digital camera, which is the equivalent of a 24mm lens on a 35mm film camera.
When making panoramic group photos, someone always moves between the exposures; it's inevitable. But, worry not! It's easy to fix these problems. Open the contributing individual frame(s) and cut the necessary face with the lasso tool in Adobe Photoshop. Drop it on top of the panorama, and then carefully scale it and distort it to match the panoramic version. Then, using the eraser set to paintbrush mode, blend the overlay into the base and, when finished, flatten the image. It takes just a few minutes to accomplish a convincing patch.
In a future installment of this column, I'll cover making object movies using the same technology but a different technique. In the meantime, you should find plenty to keep you busy if you decide to delve into panoramic photography by trying it yourself. If you like the idea but aren't ready just yet to invest in hardware and software, you can always improvise using whatever camera equipment you have and with demo versions of stitching software. Unfortunately, Apple offers no demo download of its QuickTime VR Author Studio, but some companies -- including MGI, PixAround.com, and VR Toolbox -- do provide free demo-version downloads through their Web sites.
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