Monday, July 27, 2009

Panorama Photography Part II

In Panorama Photography Part I, I discussed what panorama photographs are, and why they’re so appealing.

Now in Part II, I discuss techniques for taking photographs for panoramas created from multiple photographs, and stitched together into a single spectacular image.

There are three major rules of thumb to ensure your images can be successfully mated to make a panorama.
  1. You need exposure consistency in your photographs to ensure colors match from photo to photo which make up your image. One of the most common problems in stitching photographs together is differences in the color of the sky, due to inconsistent exposures photo to photo.
  2. You need to ensure there is enough information in adjacent photographs that they can be successfully “glued” together. This accomplished by photo overlap.
  3. You need to eliminate image parallax so that there are no ghosts in your final image and that lines in the panorama are aligned and look normal.
Galapagos: North Seymour Island

Here are my major guidelines for taking photographs to use in creating multiple photo panoramas:

  • Use a tripod to keep all your photos in the same horizontal plane.
  • If your panorama contains parallel vertical or horizontal lines, such as when the panorama includes a fence or building facade it’s important that your lens’ pivot point, or entrance pupil (the optical center of the lens), not the camera, be located directly over the central axis of rotation of the panorama. It’s relatively easy to locate the entrance pupil of a prime, or zoom lens (each focal point). By rotating your camera/lens over the pivot point, the problem of parallax, where the photographer can’t align vertical and/or horizontal lines in pairs of photographs when stitched together disappears. Really Right Stuff, the manufacturer of my panorama head has an excellent tutorial about locating a lens’ pivot point to eliminate parallax. (Please note, that while Really Right Stuff continues to call the pivot point the “nodal point,” which is an incorrect use of terminology, their method of locating the pivot point is the best way I know of to quickly locate and set the pivot point.)
  • You need to keep your exposure settings uniform throughout your images, so their brightness and color will mesh, photo to photo. You should scan the entire scene making note of the aperture and shutter speeds your camera is suggesting, then pick one pair of settings in the middle, or slightly darker to make sure any sky details are preserved and manually set it, so that the settings will remain the same for each photographic image used in the panorama.
  • Monument Valley, UtahAmply overlap each of the images in your panorama. You wouldn’t have liked my photo of Monument Valley with a white bar in it because I failed to overlap each photo enough. I overlap by 30% each time. Some say 15% works just fine, but I prefer more. Increasing the amount of overlap helps reduce “flaring” that happens when the software is forced to use all of the image frame, including the corners which may show distortion depending on your lens choice.
  • Look for movement in your overall scene. While movement in a scene can make it more interesting at times, too many or large blurry areas in your photos can ruin your final panorama. When overlapping images have items which don’t precisely match, you get a blur, which can ruin the shot. I try to take each of my multiple images quickly to avoid the problem of movement. By the way, I do realize that some movement is unavoidable. You just need to minimize it.
  • Shooting with shorter focal length lenses more often than not introduces problems of lens distortion. When there is lens distortion the stitching between side by side images can be unnatural looking. Many wide angle lenses suffer from barrel distortion to varying degrees. You can avoid this problem merely by shooting with longer focal length lenses.
  • You should also minimize the use of filters, to obtain exposure and white balance consistency between the photos which will make up the complete panorama. Polarizing filters, in particular, often darken the corners of your photographs. Depending on the angle of light to the filter they can create a significant variation in sky color from photo to photo in the panorama, preventing you from creating a combined image which looks as one. I never use polarizing filters when shooting panoramas. For that matter almost any filter can add some vignetting to your images, which interferes with good stitching and the final image, so I normally never use a filter on my lens other than the UV filter which I keep on all lenses to protect them.
  • I normally turn off auto focus and preset my focus manually for the entire group of images which will comprise my final panorama photograph. Image size can change with focus shift. If that happens, it’s likely you’ll never be able to achieve a high quality alignment of your stitched photos which make up the overall panorama image.
  • I manually set my white balance of my DSLR to eliminate color shift from photo to photo so they will seamlessly stitch together. This is especially important for landscapes showing substantial sky.
Good luck. Let me know if these guidelines help you put together your next panorama.


Stan said...

I had no idea why the few times I put together a panorama in Photoshop it looked so bad, so disjointed. Now I know why, and how to make a great panorama next time. My problem was I used auto-exposure and auto-white balance. My skies from photo to photo didn't look so different until I tried to stitch them together.

Thanks for the great pair of articles.


Sara said...

Great article Ned. Now I know how to make a great stitched pano photo. I'll be using this at the Grand Canyon later this year.


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