So what does the 18mm Sirui lens do for the iPhone SE2020. The native lens on the iPhone camera is already, arguably, a wide angle lens, roughly equivalent to a 28mm lens on a full frame DSLR. Adding the Sirui takes it into the ultra-wide range at 18mm equivalent. The two shots above show the difference pretty clearly. As important as the extra width is, the 18mm frame also contains more at the top and bottom, and, for landscapes, can be quite effective in producing a natural view of the world…closer, in my opinion, to the impression the scene makes on our naked eye. iPhone SE2020 with the Moment thin case, native lens and Sirui 18mm. Native Camera App.