07-10-2017 07:32 PM - edited 07-10-2017 08:26 PM
I am planning on using it on an APS-C XSi. I would need a helicoid if I don't use the original backplate (which I do have but contains small welded on parts which may get in the way of a simple filter. The T43 came off of a Smena Symbol with the shutter button behind the lens itself.) Wouldn't a helicoid increase the distance of the lens from the sensor too far away for it to function - not even considering focusing to infinity..