Originally posted by Adam
Your a star
Couple of points
Sigma HSM not working - Sigma state there will NOT be a fix at present
"Japan have stated that your Sigma lenses are not compatible with this converter and unfortunately it is not possible to make them function.
They have stated it is something they may look into producing in the future but there are no guarantees.
Kind Regards
Chris Bibby
SIGMA IMAGING UK LTD"
and this is wrong
"With the D FA 100mm screw drive lens, AF was about 20% faster without the converter. Thus, we can conclude that the teleconverter adds a slight amount of friction to the screwdrive mechanism."
The converter has a geared reducer (you can check turn the af screw camera side and count the turns lens side) this is true for all screwdrive converters and is why you need 'electronics' to fix in lens driven motors (have to correct focal length for AF stepping).
On the plus side in it mean in lens (SDM) does not slow dowon on the converter (whoo hooo

)