Pixiq

By now, many photographers are aware of a panorama technique that produces 360˚x 180˚ images called equirectangle projections. Normally, these panoramas are produced to be turned into QuickTime VR Movies. A VR (virtual reality) movie projects the panorama in such a way as to produce a navigable view of a scene such as a room. These movies are usually found on websites for hotels, for real estate, electronic games and many other applications. They can also be used as flattened space shown as a print. I am most interested in the latter. I love the abstract quality of these images when they are flattened printed and framed.

When shooting a 360x180 panorama, it is important to shoot images so that they are precisely on the same axis (Y axis + the vertical axis as well as at the same height). In order to maintain this accuracy, the use of a VR rig is almost a requirement.

While there are many different brands of VR devices, the basic principle is the same. Each image needs to be captured at different angles using the nodal point of the lens. The nodal point, which is sometimes referred to as the entrance pupil, is for all practical purposes, the center point in the lens. The nodal point needs to be centered on the rotational axis (the center of the tripod) for each shot taken. This location can be determined from a chart or in many cases can be roughly the center of the focal length of the lens used. I find that a rough guesstimate is good enough in most situations to produce a reasonable alignment in the final image.

Many photographers who specialize in this kind of imagery, use a handheld approach by dangling a weighted string below the fisheye lens which is held over a point on the ground while rotating the camera through 6 - 8 shot angles. This technique makes it easier to capture the ground as it does not show the tripod. As they take the images, they are careful to rotate around the string which becomes the nodal point of the lens. The fisheye lens which sees 180˚ vertically, allows the user to see the string at the bottom of the frame while viewing through the lens as they rotate through the shots. As long as the weight stays over the same spot on the ground and the camera is held at the same height, the technique works. Because the fisheye lens can capture the sky as well as the ground, the string will show at the bottom of each shot.  However, it is very easy to retouch the string from the final stitched image using Photoshop.

While the string method can be very usable, it is always best to be as accurate as possible and the use of a well designed VR device mounted to a solid support makes alignment more or less automatic.

This is a Novoflex Panorama 6/8 VR camera mount. This precision tool is one of the best choices for doing 360˚panorama photography with a digital camera. The system allows the camera to be adjusted to the nodal point of the lens and can rotate at precise angles for the lens used in order to produce the best results for stitching. The whole platform rotates around the Y-axis and the camera can be adjusted to rotate around the X-axis for single or multi row image captures. The Camera can also be adjusted along the Z-axis to set the nodal position. In order to minimize camera movement, a remote shutter cord such as the one shown above, can be useful for activating the camera shutter. This is especially useful when shooting an HDR sequence where each angle requires several shots.

The Novoflex system can be set to produce stops at different camera angles that insure that the shots overlap the right amount for stitching. Depending on the fisheye used, the stops can be set to 6 points or 8 points within a 360˚ pan. Six points are all that are required for a full frame sensor using an 8mm fisheye and eight points are needed for an APS sensor.

I tend to shoot my panoramas using a monopod and a Novoflex VR device which for all practical purposes works as well as either of the above techniques. A monopod has a slightly larger footprint than the string. The monopod is sturdier than the string and maintains the height needed in every shot. It is also much easier to retouch than tripod legs. 

Once you have your images, all you need is a great stitching program and you can stitch everything together. For my money, the best stitching program I have in my stable is PTGui.

I hope to talk about stitching applications in another post very soon. 

© John Neel

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