10 out of 10 points and recommendedMin coma min star trailing @ 30 sec.Larger than SEL1018 No filter threads
I have used many ultra wides Voigtlander 10mm and 12mm, Rokinon 12mm and 14mm, Sony SEL1018 in full frame mode at 12mm to 18mm. When you go beyond 16mm distortion is going to be there. Interior shots are a skill to adapt to and exterior a clear foreground with included background another skill in composition. I use the A7S to do mainly Astro Milky Way capture where an ultra wide can save you from doing a panoramic to get rid of bad stars on the sides and only use center parts when merged. The Rokinon's have a bad problem with star trailing in upper right and some left and some coma (dove stars) that everyone excepts at the f/2.8 but putting at f/4 or f/5.6 can reduce. The Voigtlander's small and most perfect at 10mm f/5.6 you get a 50 sec. shot to make up for the f/5.6 reduced light. The SEL1018 is just a smaller but softer on edges and some vignetting corners when doing dark captures and coma.reviewed August 15th, 2017 (purchased for $1,698)
This lens after giving a workout on several nights before a new moon as well as a full clear Milky Way night with about 50 shots in the dark and lit places was superb as the Voigtlander's. There is no worry about having just f/4 when using with the A7S because it gathers more light and to correct of coma and star trailing you have to increase f/ anyway. Any lens but ultra wides especially the camera has to be level and pointed at the center of the subject.
This lens an image zoomed to 400% in Capture One coma was min. as well as star trailing at just the 30 sec wall most do, 42 sec if in bulb. Stars in each corner were pin point as the center with no softness at the sides, Subject in foreground (a boat dock) was sharp/clear and lights/houses across the water were sharp even at f/4.
The Voigtlander 12mm and SEL1018 have screw on filters threads for this lens NiSi has a 150mmx150mm filter holder (fits perfect) so you can use the NiSi Clear night light filter or Lonelyspeck Purenight filter (for ground light and MW color/sharpness. For anything wider than 16mm a Polarizer gives uneven sky color!
Used with the A7RM2 for day shots/sunsets with awesome sharpness also handheld with IS on or tripod IS off. With some wides you get drop off up close on sides BUT not this lens.