Digital Focus: Shooting Photos for Panoramas, Part 2

Unexpected things happen as a result of technology. Who would have guessed, for example, that massive hard drives and ubiquitous Internet access would have enabled modern computer users to store all of their music on computers and pocket-sized players instead of on lots and lots (and lots) of spinning plastic discs?

Likewise, digital photography has made panoramic photography popular. Once only within reach of professionals using specialty cameras and arcane techniques, now we can all do it quite easily.

Last week, I discussed some techniques that'll improve your panoramas; this week I'll wrap up with a couple more.

Watch the Focal Length

Does it matter what focal length you use when you take a panorama? Yes, it can. Most panoramic stitching software is designed to accommodate a wide range of focal lengths, but the reality is that these programs do best, in my experience, if you stay away from the wide-angle end of your camera's zoom.

The problem with wide-angle shots is that they have a tendency to warp the edges of the picture. Like a fish-eye lens, the wide-angle mode distorts the view. And that makes it harder for your software to successfully stitch overlapping scenes together. The end result is overlapping ghost images, reminiscent of the parallax syndrome I demonstrated last week.

Here's what it can look like when you try to stitch together a scene shot with a camera set to about 20mm; I've used two shots that were stitched together approximately in the middle of the panorama.

Take a look at a detail in the scene, and you see where the software got confused trying to combine the various wide-angle images. Aside from the obvious blurring, some doubling is apparent in the downward-hanging branches to the right of the tree trunk.

Don't Neglect the Edges

When you create a panoramic photo, your computer is essentially manufacturing a wide-angle image from a series of photos. And that means the edges of the resulting panorama will, by necessity, curve in a way that makes it hard to crop the photo into a nice, even rectangle unless you discard the edges. In addition, you'll get variations in the top and bottom edges of your photos as the framing varies slightly from one shot to the next. And the more photos you include, the more pronounced the effect becomes. You should take all this into consideration when you shoot the pictures, or else the resulting panorama can be very tricky to crop properly.

Consider this simple three-photo panorama. It's pretty easy to crop, because there's only a little curvature at the edges.

But my next panorama is composed of ten individual shots, in two rows. You can see that the curvature is quite pronounced.

Keep this in mind and always shoot more of the scene than you think you'll want in the final panorama. By over-shooting, you'll be able to get a better (or perhaps more complete) final image.

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