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Tools For Measuring Camera Stability – Part 1

Posted by Tom Benedict on 09/10/2011

One of the grails with almost any form of aerial photography is camera stability. For video it’s the difference between a choppy nasty video that gives the viewer motion sickness, and a smooth clean video that gives the viewer the feeling that they’re a bird. For still photography it’s the difference between a blurry picture and a sharp one. Photo editing software can correct for the occasionally tilted horizon, but even the best deconvolution routines won’t fix a helplessly blurry shot.

The most common solution to motion blur is to increase the shutter speed on the cameras. I’ve done this in the past, and within reason it works. But eventually most KAPers will take at least a cursory look at their rig and wonder if it’s possible to make it more stable than it is: a different spacing of the Picavet lines, a stiffer pivot on a pendulum suspension, or adding some sort of stabilizing vane. Some take it to greater extremes than others, but everyone does it to some extent even if it’s only subconscious. No one likes a blurry photograph.

Any time you take on a problem like this, though, it’s important to have metrics that you can use to tell if you’re doing better, worse, or making no change at all. Sometimes these metrics are subjective. I know my photographic composition has improved over time. It’s nothing I can point to and say, “See? I’ve improved by 29.35%!” But subjectively I know it to be true. Sometimes these metrics are quantitative. I can look at a histogram on an image and know if I nailed the exposure, and how far off I was in the cases where I didn’t. Sometimes these metrics are a mix. Most KAPers keep a mental tab on what percentage of their shots are blurry. The number is quantitative, but what constitutes “blurry” is subjective.

In the case of camera stability, though, there are clear quantifiable metrics that can and should be used when evaluating changes to a camera rig. They are the rate of change in position in X, Y, and Z, and the rate of change in orientation in pitch, roll, and yaw. In the past I’ve made the argument that changes in position only really matter if you’re making panoramas because the rates required to cause motion blur in a KAP shot are extremely high. Of more interest are the rates of change in orientation in pitch, roll, and yaw. This is what I plan to discuss in the next several posts.

Before going into the technique, I’d like to point out that this topic is under discussion on the KAP Forums under the thread: Measuring Camera Stability – A Quantitative Approach. My thoughts on this subject are not universally accepted, so by all means take a look at the dissenting opinions and form your own conclusions.

In the next installment, I’ll discuss the technique I’m using, and the tests I made to verify that it works.

– Tom


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