The Perfect Lens for the Night Sky

Review By Dave Williams

Sigma Corporation has been in the game for more than 60 years, and this experience has culminated in the launch of some incredible glass. The new 20mm F/1.4 DG DN | Art lens in its lineup really packs a powerful punch. Available in an E-Mount (Sony) and L-Mount (Leica, Sigma, Panasonic) version, this lens takes all that Sigma knows about wide, fast lenses and puts it all in one place. 

This prime 20mm lens gives a field of view that isn’t unnaturally wide but is wide enough to incorporate enough of a scene to see a lot of features. In real terms, its angle of view is 94.5°. This perspective makes the lens particularly useful for astrophotography, particularly when we consider the maximum aperture of f/1.4. At the other end of the scale, the minimum aperture is f/16. The 11 diaphragm blades create a nice bokeh effect as well as precise movement between aperture values. The 82mm filter size is fairly common, and makes it easy to find compatible filters, which is something I’ve found to be a problem with the often-uncommon filter size of many ultra-wide lenses. 

I’ve already written a couple paragraphs of technical info and refrained from throwing down my opinion; but it’s time for me to open up about this lens. It’s amazing! Honestly, this is an astro dream. For years I’ve been looking for the ultimate aurora filming lens, and this is it. The whole sky opens up to this lens, flooding the sensor with light from the huge aperture. Even with an APS-C sensor, the lens is still 30mm equivalent. 

One of my main considerations with lenses is the cold, and this lens has a lens heater retainer which allows a heater to be mounted to prevent the front-glass elements from freezing or suffering condensation. This Sigma 20mm F/1.4 lens has been designed for optimum performance in even the most demanding and challenging conditions. On top of that, there’s absolutely no noticeable geometric distortion and, owing to the makeup of the 17 elements inside the lens, virtually no chromatic aberration. 

The thermally stable composite materials from which the lens housing is made means the whole thing feels very solid and sturdy. The switches and rings are easy to operate and feel very deliberate in their mechanisms. Speaking of mechanisms, the autofocus is driven by Sigma’s Hyper Sonic Motor, powering through the entire focus range in less than one second, and hitting tack-sharp focus with ease. 

The Sigma 20mm F/1.4 DG DN | Art lens is solidly constructed. It weighs in at 22.2 oz (630g) for the E-mount version which isn’t exactly small and light, but Sigma has clearly focused on the quality of the optics. The images are very sharp. This lens is an unrivaled new addition to the Sigma range: It’s the brightest, widest, full-frame lens out there, and it’s a perfect addition for any astrophotographer or ultra-wide landscape photographer’s gear haul.