Teleconverter magnification comparison. (5 imgs)

Started Aug 25, 2013 | Photos thread
OP brandrx Forum Pro • Posts: 28,337

MightyMike wrote:

I'm sure we all know that if the locking pin doesn't go into place the screw drive shaft will not connect as that locking pin is connected to the cameras screw drive. Keeping the locking pin depressed (voluntarily or involuntarily) will make the AF not work. This is purely mechanical and not electronic. now if AF makes a sound and tries to work then the data pin is connecting perfectly, if not then the data pin isn't connecting. As absurd as it is I'd suggest that all the Sigma TCs are all off by just enough not to lock into place with some Pentax lenses and likely by making the locking-pin hole larger one can give the tolerances necessary to make it work. It could also be that (*) lenses are built to much stricter standards than cheaper lenses and some Sigma TCs could have enough variance to not lock into place with such strict standards.


I will step back in here for just one last bit of info and then I am for sure through with this thread.

With my Pentax-A SMC 400mm f5.6 lens: (1) My Sigma 1.4X APO EX DG, Sigma 2X APO EX, and Sigma 2X APO EX DG will not lock into place. (2) My Sigma 1.4X APO EX will lock into place.


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