I have a Switar 12.5-100mm zoom I use with Bolex cameras (non TTL auto-metering version). I want to use it with the appropriate 6.5mm Asheron wide angle attachement (which I don't have yet). My lens does NOT have the knob marked "aspheron" at the back of the barrel.
Firstly, what exactly does this knob do - compensate back-focus for when the Aspheron in attached?
Secondly, can I use an Asheron 6.5mm with my 12.5-100mm lens (that doesn't have the knob marked "aspheron")?
Has anyone been down this path before?
Thanks in advance...Greg
