[YodasLuke]

Yodas Luke

You wrote-: "Measuring a radius of a circle from an oblique camera angle can give you an invalid reading. Any measurement of the hand of a clock should be taken when facing the clock."

That's perfectly correct. I am presuming that all readers understand that all my photographs are only representative - that they are 2-D images of 3-D motions, and that there will be perspective distortion due to an imperfect camera angle relative to the relevant clubshaft/hand plane. However, I do not believe that the fundamental principles that I am attempting to demonstrate are incorrect - because of these camera angle problems. For example, the clubhead arc of Tiger Woods driver swing (from the Nike commercial) is obviously distorted because the camera angle is face-on - while the clubead arc motion is on the inclined plane. However, it remains a "fact" that the radius of the clubhead arc (relative to the swing center) is very different at different time points during the downswing and followthrough, and that the swing center cannot be conceived to be the dead-center of a circle of the clubhead arc's rotational arc motion in space. The same "fact" applies to Tiger's hand arc photo - it is only representative because the camera angle is not perpendicular to the hand arc's circular arc of motion in space.

Jeff.

The picture on the cover of Search for the Perfect Swing is a good series of time-elapsed photos. The picture's also found in Chapter 3, with explanations. It's a worthwhile read.

When you wrote: "The hand arc is not as circular as the clubhead path."

I don't know how you can arrive at such a conclusion, with or without faulty camera angles.

Let's make the geometry simple, if anyone else is going to learn anything. And, we'll consider the center of the circle the left shoulder, since it's the top of the radius. Let's call the left shoulder "A". We'll call the hands "B" and the clubhead "C".

Scenario #1, Hands:
If the distance between "A" and "B" remains somewhat constant (Extensor Action), "B" should inscribe a circle on a piece of paper, like a compass. If we complicate it by letting "A" move (like the golf stroke), the circle becomes somewhat elliptical.

Scenario #2, Clubhead:
If we measure the distance between "A" and "C", we have to consider the cocking and uncocking of the left wrist (shortening and lengthening of the radius).

Scenario #1: Constant radius = circle

Scenario #2: Changing radius = not a circle

So, I'm not following your quote.