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02/16/07 Panorama Photography (continued)

Things to watch out for when shooting photos for a panorama:

First we must try our best to avoid parallax errors. Keep vertical lines straight by keeping the camera level. A tripod is very useful. A quick demonstration will illustrate parallax errors that are often overlooked. Close one eye; hold your arm out straight and point at an object about 15-20 feet away. Now, without moving switch eyes, are you still pointing at the object? Go back to the original eye and point at the object. Now, keeping your arm still, turn your head left and right (side to side) while continuing to look at the object. Were you still pointing at the object as you turned your head side to side? This shows how foreground objects can change position in relation to background objects if you are not careful when shooting images for a panorama, causing alignment problems in your final composite image. In the last example you naturally turned your head about your spinal column that caused the eye you were looking through to swing from side to side. Try it again, but this time try to turn your head side to side on an axis through your open eye and keep your finger pointing at the object.

To avoid this same scenario with your camera it is best to put it on a tripod when shooting panoramas. If you really want to get serious you need to find the point of no parallax (often referred to as the nodal point) of each camera and lens you use. You will also need a special tripod adaptor. This is beyond the scope of our discussion today and I will direct those interested to the following links.
http://photography.about.com/od/panoramas/a/a020505_5.htm
http://wiki.panotools.org/Nodal_Point
http://www.vrphotography.com/data/pages/techtutorials/technotes/nodalptalign-tn.html
http://www.geolit.org/process/nodal.htm
http://doug.kerr.home.att.net/pumpkin/Pivot_Point.pdf good paper
http://www.janrik.net/PanoPostings/NoParallaxPoint/TheoryOfTheNoParallaxPoint.pdf

To shoot panoramas without a tripod or monopod you can still minimize parallax errors by focusing on good technique. Keeping the camera level, you need to rotate around the camera between successive images. The best way I know of doing this is to position yourself so that the camera is directly above the ball of one of your feet. Then rotate on the ball of your foot between images.

This leads to an important point. Make sure you overlap successive images by at least 20%. Your camera may have a panorama mode to assist you. Otherwise pick a prominent feature near the edge of each frame and be sure to include it in the next frame as well.

Second try to avoid lens distortion. Wide angles lenses often distort the sides of the images. Although these images can still be stitched together in Photoshop and other task specific programs, it is often much easier to shoot more images with a longer focal length to obtain the same coverage.

Third avoid exposure variation between images. Panoramas don’t look very good when some images are brighter than others or have different color casts. These differences can be fixed in Photoshop but it is easier to avoid them in the first place. You don’t want the camera making individual decisions about aperture and shutter speed for each image that you will be stitching together. You need consistency. That means shooting in manual mode or utilizing exposure lock. If your digital camera has a panorama feature it might automatically employ exposure lock, read your manual! Consider starting your first shot while aiming at the brightest part of the scene to be included in your final image.

Forth avoid moving subjects. Movement makes image alignment difficult. Clouds move so shoot carefully but quickly. Ocean panoramas and blowing plants are particularly difficult. Also watch to make sure that a moving object doesn’t travel with you as you rotate and appear in more than one image.

Well enough setup it is time to get out our needles and start stitching.