I like to think of coil as a paint roller. Pretend that your coil is loaded with paint, and that you're trying to paint ground that you're walking across. As you slowly sweep coil back-and-forth across ground imagine paint being applied. You're trying to paint entire area you were trying to cover. If you can imagine paint, you should be able to cover entire area without missing a single spot.

I love panoramas. There's something very appealing about their shape. It's probably because we see world more in these dimensions than near square format of standard film/sensor frames. It might also explain upsurge in popularity of widescreen TVs!

Panoramas have a reputation of being hard to take. There are dedicated panorama cameras available but unless you've got at least a thousand dollars to spare, you probably can't afford one! But you can take panoramas with any kind of camera.

All a panorama is, is a sequence of images where you turn slightly for each different frame. In old days, before PCs and likes of Photoshop were around, you'd take your prints (there wasn't much point in shooting panoramas on slide film, for obvious reasons), lay them out on a table and position them over each other where they overlapped. A bit of sticky tape held them together. [As a side note, this technique was used by NASA to build up mosaic pictures of planets and satellites their spaceprobes visited, up till late '70s/early 80s when computers were introduced to make process less laborious].

Now that PCs and image manipulation packages are easy to come by, high-quality panoramas can now be created by anyone. If you're shooting slide or negative film, you will need to have your images scanned before you do anything else.

DIY Panoramas

The idea behind taking panoramas with SLR cameras is that camera is rotated around its nodal point during each successive exposure. What's Nodal Point? It's point inside your camera where light rays converge and flip over. It's different for different focal lengths (on zoom lenses) and for different prime lenses (fixed focal length lenses like a standard 50mm lens). It's important to rotate about this point to eliminate image mismatches due to changes in parallax. Parallax is apparent shift of an object against a background due to a change in observer position.

Just to be clear, Nodal Point is not same as film/sensor plane. Generally, for most SLR cameras and lenses, Nodal Point is located somewhere towards center of lens barrel and lies in front of image/sensor plane.

The Problem With Parallax

Parallax is easily demonstrated by a simple experiment. Hold up your finger about 1 foot in front of your face and alternately open and close your left and right eyes. You'll notice that your finger shifts left and right with respect to background depending on which eye is open. Try another experiment: With your finger still raised, close one eye and turn your head from side to side. Notice how your finger moves with respect to background. This relative movement is due to fact that you’re not rotating your head around your eye’s nodal point, which is somewhere in center of your eyeball. Instead, you’re rotating about your spine which is several inches to rear and off to one side. It is this relative side-to-side motion that we try to eliminate when setting up a camera for panoramas. [If you want to read up more about parallax, Wikipedia have a good explanatory article.]

Now, if you consider a camera held up to your face - it will suffer even greater parallax errors as it's farther from your spine (the point of rotation of your head) than your eye. It's surprisingly common for people to take panoramas in this fashion and then find individual pictures don't match up.

So use a tripod and rotate camera on tripod. The parallax errors will be significantly smaller but there will still be some error involved. However, images will match up better than with head rotation method.

Mechanical Contraptions

What perfectionists strive for is to have camera rotate about nodal point. There are brackets and contraptions available that will let you offset your camera from tripod's axis of rotation and with a little experimentation and trial and error, you can position your camera so that its nodal point is directly over axis of rotation of bracket. Getting this spot-on means your images should line up perfectly.

A few months ago I bought such a bracket - Kaidan Kiwi. This comes in two halves which produce an L-shaped bracket. Its instruction manual explains how to set it up and find nodal point for your camera and lens. However, you have to get your tripod perfectly level before using it, otherwise you end up with a curved panorama rather than a straight one.

I've had good success using this bracket, but it is large and heavy and certainly a bit too cumbersome to be carrying on long walks or while away on vacation.