My understanding is that lens IS includes actuators and sensors for 2 axes of movement in all IS-enabled lenses, whether Sync IS or not, i.e. the lens only stabilizes for pitch and yaw and nothing more. On the other hand, current sensors are stabilized for 5 axis (pitch, roll, yaw, left-right and up-down.
Sync IS adds synchronization capabilities, i.e. to use all these 2+5 actuators and sensors in the optimal way to correct a certain motion of the camera.
Do you think that lenses with Sync IS capabilities have actuators for other axes? How would that work? Lens IS works by tilting a lens element to compensate agains the pitch and yaw of the body/lens combo as seen on this nice animated gif:
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I am not aware of any lens where there is in-lens IS for any more than these two axis - if there is such a thing, I would be truly love to know how that works. Rotating a lens element won't rotate the projected image, so in-lens roll correction is pretty much out of the question, but left-right-up-down shifting of the image would be challenging too - much more so than doing that at the sensor.
Some of your points like the 300pro seem valid, but I don't think the Panasonic lens plays into it as much as you're giving credit. Given a choice of similar lenses most folks choose the one from their own camera brand. People who own Olympus are getting rid of their PL100-400's in favor of the new Oly version.
There are two statements here: 1, the 300/4 uses special gyro sensors and 2, such sensors are required for sync IS. The first may or may not be true, but either way, does not necessarily imply #2.
(Side note: Sync IS is a lens-camera communication function, not an extra component in either. OM-D Sync IS is amazing and way better than Panasonic Dual IS, but the concept is the same, just Panasonic decided to make it more widely available. When you synchronize superior lens IS and superior IBIS, you get better results.)
Interesting report. I am wondering, however, about your use of S-IS-Auto. This is the very unfortunate (IMHO) option Oly makes the default. For regular shooting, S-IS-1 is really the better option. [...] Otherwise I think that another try would be very helpful, using IS-1.
In any event, the likelihood of Olympus taking the cripple hammer to a mass market zoom lens in order to prop up sales of a lesser market prime lens is rather far-fetched. They are completely different optics.
My understanding is that lens IS includes actuators and sensors for 2 axes of movement in all IS-enabled lenses, whether Sync IS or not, i.e. the lens only stabilizes for pitch and yaw and nothing more.
Looking into it further, I believe you are correct. 12-100, 300, and 100-400 lenses all appear to have pitch and yaw movements in the IS lens element.
Apparently Olympus worked with Seiko Epson on their Gyro ICs to develop a special one that is 10x better than previous ones and is what is used in the E-M1X which is why that model is a full stop than the other E-M1 series. These special gyros may also be used on the 300 PRO lens. No idea what the cost of these sensors are, but it could be (in the low volumes Oly would buy) that they are expensive enough that including them in the 100-400mm pushed the final cost up to high.
The 300 PRO is actually a stop less stabilization than the 12-100 PRO. This may be partially due to the 300 PRO using three elements in its "stabilization element" where as the 12-100 PRO uses two, so heavier in the 300 PRO and thus probably harder to move as quickly. No idea what the 100-400 is using.