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Panoramic vs. Spherical Virtual Tours. Which to Choose?

By Joseph Ortiz, President, IPIX InfoMedia

Like many technical specialties, there are many options and "speeds and feeds" related to panoramic photography. Considerations go beyond the simple quantification of total cost. Yes, at the end of it, cost will be the most tangible consideration. But for approximately the same cost, you will have a wide range of options available. How do you decide which is best for your need?

Creating a virtual tour is, after all is said and done, a photographic process. More specifically, it is a panoramic photography process. You should consider two areas when deciding on an approach:

No matter which type panorama capture approach you choose, you will also have to consider which type of camera to use. We'll first cover the camera selection.

Rather than compiling a primer on camera selection, I'll share a few key points to keep in mind. First, decide on film versus digital. Then, balance your needs for particular resolution and other features versus cost and time.

Film Cameras

Choose film over digital if you want to lower your upfront camera cost and don't mind paying for hardcopy archival prints. Use film if you need to capture a scene in which there are dark showdown details in the same frame as brightly lit detail. In these cases, film captures a higher dynamic range than most digital cameras. Finally, use film if you want to get more resolution for your camera dollar investment. More resolution is better for Panoramas. You can scan at very high resolutions. Choosing either 35mm standard or Medium Format will provide you with a larger visual frame to scan compared to most sub-$1000US digital cameras.

Digital Cameras

Depending on how much money you want to spend on your digital camera, you can obtain the benefits of film mentioned above as well as the benefits of digital. The key benefits of digital are instant gratification and review subsequent to shooting and no variable film processing costs.

• Most sub-$1000US digital cameras offer a relatively low dynamic range. Certain "linear scan" digital cameras (see www.panoscan.com) offer a dynamic range quality that meets or exceeds the best film can offer. The resolution that Linear Scan digital cameras can capture is also the highest possible today from digital cameras. The cost, typically $10,000US or more, makes this option limited for most.
• All digital cameras, from the low-end to the high-end have increased in resolution over the last 5 years. Consumer level digital cameras with 5 million pixels ("5 mega-pixels") can be found now for $500US or less. These cameras will typically have a fixed lens with 2x or 3x optical zoom. Higher zoom levels (8x or 10x) will cost a few hundred dollars more.
• Digital SLR cameras with 6 million pixels can now be found for under $1000US. Higher end "full frame" models can cost up to $5000US. These units take interchangeable lenses, typically a "Canon-Mount" or "Nikon-Mount".

In general, when choosing a digital camera for panoramic photography, stick to the following guidelines:

Capturing Panoramas
Once you've considered your camera option, you need to consider which of the several different ways of capturing panoramas makes the most sense for your needs. You have a number of ways to produce a panorama. These include the following, which are sorted generally from easiest to hardest as well as from lowest image quality to highest image quality:

• Freehand Stitching:
  Freehand stitching works with any camera that you can put into Exposure Lock mode. To take a panorama, you point your camera at the left end of the area of interest and take your shot. While looking through your view finder, you move the camera to right, leaving an overlap in your viewfinder relative to what you shot in your previous frame. Take your next frame and repeat the process. Once you complete your panorama shots, you need to use stitching software to put the images together. To get a good result, you will need to manually match points in each frame with the corresponding points in the overlapping frame. Freehand stitching is best used for the occasional panorama that needs 4 shots or less to take.

• Parabolic Mirror:
  Parabolic Mirrors are devices that attach to your camera that allow you to capture a 360o field-of-view in a single shot. Most parabolic mirrors, like the one offered by www.surroundphoto.com include special software that processes the "donut" image and output a viewable panorama. Shooting a panorama with a parabolic mirror can be done freehand or with a tripod. When shooting freehand, you will need to hold the camera and mirror over your head. You will get a more professional quality image if you put the camera and mirror on a tripod and use your timer to physically get out of the shot. Parabolic mirror panoramas require only one image to be captured, but unless you shoot with film and scan at a high resolution, or use a more expensive high resolution digital camera, your images will be of a lower image quality when compared to the other panorama capture approaches using the same type of camera. Using a single shot does have the benefit of cleanly capturing imaging with a large amount of movement in the image. One other consideration of mirror systems is that the vertical field-of-view (what you see looking up and down) is generally limited to about 100o. Be careful to understand which 100o out of the possible 180o the mirror is looking at. Depending on which parabolic mirror you choose (and there are about a dozen to choose from), the vertical field-of-view may be set for a residential real estate property vs. a hotel property vs. a live event vs. security or teleconferencing.

• 2-Shot Fisheye:
  Fisheye panoramas are the easiest way to capture a Full-360o. You can see not only in every direction left-to-right, but also every direction top-to-bottom in this panorama. Solutions like those offered by my company, Internet Pictures Corporation www.ipix.com, include an off-the-shelf camera, fisheye lens, tripod/rotator and software for stitching and editing the panoramas. With this type of system, you generally need to shoot using the tripod/rotator. The system allows you to shoot a front image and then rotate the camera and lens to shoot the back image. Image pairs can be then stitched into the final Full-360o panorama. Because this type of system requires 2 images to capture a panorama, the resulting resolution will be greater in general when compared to mirror systems. While not as easy as mirror systems, 2-shot fish-eye systems can be used to capture scenes in which there is a large amount of movement. This can be done by aligning the boundary between the front and back images onto an area when movement is not taking place.

• Multi-shot Panorama:
  Multi-shot panoramas are the most cost effective way to capture a high resolution 360o left-to-right field-of-view panorama. By taking 12 to 24 images using a camera and panorama tripod head, you can carefully photograph an area and stitch the images together into a potentially very high-resolution panorama. There are many companies that offer multi-shot panorama stitching software, including iSeeMedia (www.iseemedia.com), Arcsoft and others. You will also need to purchase a tripod head. While this photography option does allow you to shoot either a very high-resolution panorama or to purchase a lower resolution camera, if you don't need high-resolution output, you will face a more difficult capture process. First, the large number of images you must capture increases the actual difficulty in shooting and increases the storage requirements for your memory card and computer hard drive. Second, this process requires no movement within each frame, or at best a careful staging of the photography in locations where there is movement. The resulting panorama will have a limited vertical field-of-view, so if looking completely up or down is important, this approach will not be satisfactory. You can shoot what are called multi-row panorama to capture a Full-360.

• Linear Scanning Camera:
  As was discussed earlier, the Scanning Camera is the high-end digital camera. These cameras are designed with panoramic photography in mind since they offer the ability to scan an area up to 360 degrees. These cameras are professional grade systems that will beyond the scope of any unqualified photographer. The images created from a Linear Scanning Camera typically have exception dynamic range and high resolution. Resolution from these cameras will vary according to the number of steps in each rotation. A lower resolution image can be captured in about 1 minute, taking 100s of steps or linear scans in the process. A very high-resolution image may take up to 15 minutes and would include 1000s of steps. Because of the scanning nature of these cameras, scenes in which there is movement will result in odd-looking artifacts within the image. These cameras are ideal for staged shoots in which the location can be guaranteed to be movement-free. The vertical field-of-view from these cameras will depend on what type of lens is used. To get a Full-360 degree image will require a fish-eye lens.

Joseph L. Ortiz is a technology development and commercialization consultant. He most recently was Officer and VP at IPIX Corporation, managing the InfoMedia unit. Mr. Ortiz defined the strategic vision and business plan, restarting the IPIX Virtual Tour Photography and Movies business. He was regional business unit manager at Philips Consumer Electronics and has held various senior technical and business positions. Mr. Ortiz holds an MBA from Arizona State, an MS in Computer Engineering from the University of South Carolina, and a BS in Computer Science from Georgia Institute of Technology. Mr. Ortiz can be contacted at 865-220-6544 or joseph.l.ortiz@gmail.com Extended Bio...

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