B & W Kaesemann CP question

I have a Calumet branded Circ. Pol. (made in Germany) that is a decent filter, but one thing bothers me. It doesnt have a start or stop position. I can spin it all the way through the range and instead of having a stop point, it just spins into the starting position. Not sure how to explain this, or what terms I should be using. Do higher quality B & W or Hoya circular polarizers have a clearly defined starting and stopping point, ie: they only have a certain degree of travel before they hit the end of their range?

There is no start/stop, and should not be a start stop.

If you rotate the camera - would there then be a logical "stop" to how much it would be meaningful to rotate it?

If you adjust the CPL until you get the effect you want, and then rotate the camera 90 degreens CW - then you need to twist the CPL 90 degrees CCW to maintain the same effect.

So you just must be able to rotate the ring freely. Note that a rotation of 180 degrees gets you back to the same result.

i see, didnt even think about that aspect. thanks

Note that a CPL doesn't have an effect that can be calibrated 0 to 100%.

It has an effect that has a minimum or maximum depending on how the ring is rotated in relation to the angle that the reflected waves are oriented. So there can never be a marking on the ring saying "max effect" - if you have a light source that sends out polarized light, then you can change how much of light that gets through the filter by aligning your filter with the light. Rotate the light source 10 degreens, and you need to rotate your filter 10 degrees too, to maintain the effect.

The angle of polarized light is just like the magnetic field of a magnet - you can rotate the magnet and will then rotate the orientation of the poles.