First of all, prior to retirement I was working 25+ years with coordinate measurement systems - the first 8 years as an employee for a manufacturer of such systems, then as self-employed as an adviser for companies who use such systems. Whereas during the last years I earned my money by inventing and implementing solutions for tricky inspection problems in quality control, and writing software as a user friendly front end for such solutions (not all users are engineers), before I was also heavily involved in writing software to map and correct machine-inherent errors which cannot be fixed by hardware solutions. Since that time I may have forgotten a lot of the most complicated mathematics involved, but I still have the "built-in" feel to "think" in moving and rotating 3D-systems - a lot of people (and, for some reason, most women) cannot "think" in 3D geometries.

With this background in mind, I must correct some of the misunderstandings in the last posts, before they enter the public knowledge base and will be repeated in postings for the next 10 years:

@RioRico:

Quote: I'm anxious to see a 5-axis (5-dimension) SR system.

It is a 3-axis (3-dimension) SR system, using 5 of 6 possible parameters of the coordinate transition matrix. Pentax does use 3 parameters.

This link

Olympus OM-D E-M5 Preview: 1. Introduction: Digital Photography Review
offers a drawing which exactly shows what the Olympus system does.

@Quicksand:

Quote: "This is all such marketing silliness. Axes are not the same thing as degrees of freedom, and we're talking about the latter here. And this is for motion sensing only! Compensating for more than three kinds of movement (horizontal, vertical, rotational) at the sensor makes no sense. Pentax already does this."

This is just not true. To translate complicated matrix mathematics to real world language: you can shift along and rotate around every of the 3 axis, where shifting can be in 2 orthogonal directions. This would make 9 possible alterations of a coordinate system within another coordinate system. However, there would be redundant information embedded. In fact you can describe any such movement by 6 instead of 9 parameters. To translate for better imagination: you can shift in 3 orthogonal directions, and rotate around 3 orthogonal axis, so 6 transition parameters are involved. Olympus uses 5 of these, just ignoring shifting along the optical axis. And this missing one just effects focusing (distance to the object); that's why I said in a previous posting it may effect macro only.

The Pentax system does NOT compensate the 2 additional rotations shown in the drawing in the

*dpreview* link. It shifts along 2 axis and rotates around 1 axis. This is more than some of the competition does (or did): when Pentax introduced the system, they were proud to announce their sensor also rotates around the optical axis, which many of the other systems (at that time?) didn't.

@Lowell Goudge (posting of 02:59):

Quote: "Since rotation is only a combination of x and y axis movements"

This is not true, neither in the mathematics involved, nor in the technical implementation to correct it. "Shifting" in mathematics as well as in natural language usually is a synonym for "parallel shifting" - if you hold a point of a device fixed and "shift", you really do "rotating" (in fact you are using a lever around the "fixed" point).

Of course you expressed very cautiously, using "move" instead of "shift". But then you said x-movement and y-movement - which, in my understanding, means shifting, excluding rotation.

Quote: "The use of the word axis or more accurately degrees of freedom"

- that statement is of course correct if you have a look at the underlying mathematical theory. And it is needed if you are dealing with multi-dimensional (>3) systems - which does not apply for mechanical problems. However, no one living outside mathematical theories (and physics/mechanical engineering) will understand it correctly. I prefer to use an "axis" model when explaining things to non-professionals.