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Taking Handheld Panoramic Images

2. Generating good handheld panoramic shots

You can create a decent looking panoramic image with out a tripod. It will not be technically perfect, since you cannot rotate the camera precisely. But you can minimize the defects by:

Starting small. Fewer shots and smaller images are easier. At first, try a single row instead of double row panorama. If you want to capture the entire scene, capture 2 x 180 degree panoramas, as a 360 is much harder to stitch, since there is less room for fudging the errors.

Excluding close up objects. The closer an object is to the camera, the more it will be affected by parallax, a distortion of the relative placement of an object in space. Parallax helps us see in 3d, but it will cause ghosting in your panorama.

Setting focus and exposure manually.  Preplan the shot, by scanning, watching the exposure, and selecting settings that are in the middle of the range.  If you can’t manually set your exposure, setting it on that middle scene is a good alternative. Focus works the same way, but is not a problem if you are shooting a distant vista.  If you can lock it do so.

Overlapping by at least 30%. Overlapping the individual shots by a generous amount gives the software more data to use in stitching. It also minimizes the chance that you will create a gap. For these shots, don’t worry about keeping a precise overlap. The software will figure it out. You will want to avoid moving objects in the overlap if at all possible. They can cause ghostly headaches.

Keeping the camera at the same level. Look at the horizon, and keep it at the same spot in the frame. Practice is the key to keeping your camera level as you rotate.

Taking shots outside of your intended final crop. The handheld variations will require cropping – plan ahead for it. Use a wider lens, rotate the camera into portrait orientation, or zoom out to give yourself more leeway.

Taking duplicates. You can choose the best ones – people move, clouds and lighting change. I like to take one complete set, then repeat at a little different orientation. Another strategy is to take a horizontal or vertical “patch shot” as I go.

Trying to rotate around the camera, rather rotating the camera around you. One method is to hold the camera over your foot, and rotate on your big toe. Another handheld method involves holding the camera against the bottom of your chin and sighting through the middle of the lens to a spot in the ground. The person then rotates keeping the camera aligned with the spot, and the head level. You need to be able to visualize the area covered by your lens so you can rotate effectively. Don’t get too caught up on the nodal point issue. It really doesn’t matter if the objects in the picture are far away. Getting the camera level will have more of an effect because of the need for a final crop.

3. Handheld Panorama Results

For an experiment I took the same panorama three ways: first with the camera at arms length, rotating on my heels, then as close as possible rotating around the camera, then rotating around the camera, but deviating the angle by 10 degrees or so as I panned.

Using Autostitch , one of several free stitching programs; gives pretty good automated results. Be sure to rotate the images before hand, or by setting the appropriate options setting. We have an  Autostitch tutorial {link}here. If you want to get a bit more serious, Autopano Pro {link} is a recommended stitching software with the Autostitch technology (and a lot more) built in.

I tried to simulate a basic “point and shoot” situation, walking up to a view and shooting away with my Canon S70.  The camera was held in portrait orientation to maximize the vertical coverage. The metering  and focus varied across the shot between 1000 and 2000th of a second.  I tried to shoot quickly to minimize issues from changing light as the clouds blew past the sun.. The point was to push the boundaries, and show which variables are most important. A quick look at the pictures shows that all three are in need of a crop, but that the tilted shots are the worst. This is the #1 thing to keep in mind when shooting panoramas. #2 would probably be lighting/exposure, but even that isn’t horrible. Panoramas are more susceptible to high contrast issues since the pan drastically changes the location of the sun.

Results: 
My technique in this test was not my best. Both of the rotate camera and rotate person methods drifted from horizontal significantly. (2802  pixels high or 7.5% error for person rotation, 2704  or 4.2% pixels error for camera rotation height with 2592 pixels being ideal.) However, neither was as bad as the intentional tilting.  It has drop outs where I lost some of the foreground. The reason that the gap is small is that the overlap saved me. Other pictures contained most of the missing shrubbery. Here they are:



Image One, rotating the camera around me is the best of the three, though it will require cropping. The section with the stitching error is highlighted.




Image Two, rotating myself around the camera, has more drift. The red tint shows the required crop.




Image Three, intentionally tilting the camera as I rotated, is clearly the worst.

In rotating the camera, I was able to keep a steadiest hand, but what about parallax? In scanning around each image, I found an instance where a fence was misaligned. (See Image One for an indication of the area.) In all honesty, it could be an issue with rendering of diagonal lines, but it was detectable at 300% magnification. None of the other areas of overlap showed any problems. I restitched the images in Autopano Pro, and didn’t have the problem. (It has smartblend, which covers for such errors.) Still, it is not a big deal. In order for the error to begin to matter, you would need to print the image at 24 inches x 9 inches. Even then, you would need to stand 5 inches or so away to see it. My conclusion: for vista type pictures of far away objects, don’t worry too much. But try to keep the camera as level as possible.

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This article was written on Wednesday, October 3rd, 2007 and is filed under Mastering Skills. For more articles about: Photography (6), panoramic photography (3)

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