Sigma 1850 and Longteng 1770 should not be compared. Sigma 1850 has a fast focusing speed. You can switch to automatic servo focusing mode to see if the focusing speed is fast. High definition and good color. The advantages of Longteng 1770 include super wide-angle direct focus, which can be mastered in one mirror, bright in color, rich in dimensions and clear in imaging, whether it is shooting static images of flower figures or urban scenery.