see also:

• mirrorless camera systems
• https://www.sigma-global.com/en/cameras/sd-series/#sd

• Sigma SA mount has a relatively long sensor to lens flange mount designed for dSLRs

• Sigma sd Quattro
  • Foveon x3 Quattro APS-C size 39mp sensor
  • introduced Feb 2016

• Sigma sd Quattro H
  • Foveon x3 Quattro APS-H size 51mp sensor
  • introduced Feb 2016
  • reviews:
    • https://fstoppers.com/originals/fstoppers-reviews-sigma-sd-quattro-h-mirrorless-camera-272889