I'm in the process of changing from a FF Canon SLR to a crop-sensor model. I want to keep using my existing Sigma 8mm lens for CFWA, but the circular frame of the lens still cuts across the corners of the APSC sensor. I wondered if anyone else has tried using this lens with a teleconverter for a more exaggerated perspective. I'm particularly wondering if the lens can still be used on autofocus when using a teleconverter as I've read some posts in regular photography forums that suggest it might be possible to use a 1.4 converter, but very little info has been given on the subject. I've tried searching Wetpixel but the results show posts containing any of the keywords, rather than all.