IS in Canon lens with active adapter / active SpeedBooster

Well I have not tried a focal reducer adapter (popularly known by the Metabones brand name "speedbooster") on a M4/3 camera. But I have used focal reducers on a NEX6 body and electronic adapters on the Sony A7r.

They integrate well with the Sony camera body and aperture and shutter speed can be controlled seamlessly. You can hear the IS working. Presumably it works well because great Canon lenses are capable of capturing great images. As the IS is very much on on lens operation and automatically tuned to the lens it inhabits where in-lens I presume that it works fine. I have not seen any problems from using it.

The lenses you talk about are big lumps of lenses and as my favourite M4/3 shutter squeeze is a GM1 even this wild guy is not about to fit one on to the GM1. The 70-200mm f2.8 IS might be worth a laugh or two but not really practical.

Smaller EF lenses might be a little more suitable but even the 50mm f1.2 is quite a lump and not image stabilised of course. Perhaps lack of AF is not such a huge bother as even when the AF works in the Sony environment it is often quicker and easier just to use MF anyway.

I often wish 4/3 sensor users would just use FF equivalents to compare lenses like all other sensor format users do. I know that the markings on M4/3 lenses are correct and that a simple x2 multiplication can compare but once the use of focal reducer adapters is considered with lenses nominally rated for FF focal length are considered there are three considerations: the branded focal length; the correct focal length on a 4/3 sensor camera; and the full frame equivalent length. As an old hand who can visualise roughtly what a FF equivalent lens might produce it becomes a common index that allows cross format mental comparisons. I am not advocating changing the markings on M4/3 lenses but just asking for FF eq to be used (and noted as such) in comparing lenses cross format where the nominal markings on the lens say one thing and the effective focal length is also further altered by a focal reducer adapter.

Of course old rusted in M4/3 users will have mentally recalibrated to 4/3 sensor focal lengths. But having aps-c, FF, Pentax Q and 4/3 sensor cameras not forgetting the Ricoh "28mm" lens is always considered thus even though it is marked correctly to its equivalent for its sensor size. What the Nikon 1 series and Sony R100 might be in "true" focal lengths I have not the foggiest but if they are talked about in FF eq then there is a common index for comparison. From what I can see the 4/3 sensor system chat is unique in its correctness.

Hah! the much revered Panasonic LC1 (pre 4/3 system) even had its zoom lens scale marked in 28-90mm FF eq focal length whilst the lens of course said 7.0-22.5mm (whatever that meant to anyone) f2.0-2.4. (looks like 4x or half the size of the 4/3 sensor inside - 2/3" sensor)