Sigma released a new firmware for their amazing Sigma 18-35mm f/1.8 DC HSM Art lens, and now the Canon EOS C100 is supported. Very brief statement by Sigma:
Autofocus is supported at any aperture value when used with the Canon Digital Cinema Camera EOS C100.
Fine! Before updating the lens’ firmware you have to update the SIGMA Optimization Pro software to version 1.2.0.
Sigma 18-35mm f/1.8 DC HSM Art price check: Amazon USA, Amazon CA, B&H Photo, Adorama, Digitalrev, KEH Camera, eBay US, Canon USA, Canon CA, BestBuy