The following chart presents a comparison between basic parameters of the Vlitrox and other full frame 20-21 mm f/1.8-2.0 instruments. It can be noticed that the Viltrox is optically the simplest lens but it has some serious heft to it,. In our chart it is physically the biggest and the heaviest. Apart from that it also comes with the biggest filter diameter and the highest number of diaphragm blades.
In the photo below the Viltrox PFU RBMH 20 mm f/1.8 ASPH is positioned between the Sigma A 35 mm f/1.4 DG HSM and the Voigtlander Apo-Lantharem 65 mm f/2 Aspherical 1:2 Macro.
The tested lens starts with a metal mount without any contacts which goes round a rear element, 28 mm in diameter. The element doesn't move and is surrounded by a well matted, black bottom.The lens seems to be sealed and properly blackened from this side.
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The proper barrel of the lens is made completely of metal; it starts with a ring on which you can find the serial number and a white dot, making an alignment with a camera easier.
Another immobile ring has a bit bigger diameter and it features a very useful and clear depth of field scale with markings by f/1.8, f/2.8, f/4, f/5.6, f/8, f/11 and f/16. On the right side of the scale there is also the producer's logo and on the left a red badge with DF-RBW letters.
Then you see a manual focus ring as wide as 22 mm, covered by metal ribbing. On the ring you can find a distance scale expressed in meters and feet. The ring's working range is about 150 degrees, which is quite enough for precise settings. The ring's performance, however, cannot be called perfect because there is a difference in resistance; it is greater when you turn the ring toward shorter distances and less pronounced when you move toward infinity.
Further on you see a narrow (just 8 mm of width), ribbed aperture ring. It is de-clicked and features markings at all aperture values apart from f/11. Behind that ring you find an immobile part of the barrel which turns wider after a while; it features the name and parameters of the lens.
The front element doesn't move, is quite distincly convex and 55 mm in diameter. Round it goes a part of the barrel etched with the name and parameters of the lens and a hood mount. The mount is used to fix a petal-type hood and a small extension for an 82 mm filter.
When it comes to optical construction you deal here with 12 elements positioned in 9 groups. Three elements are made of low dispersion ED glass and one is double-sided aspherical. Apart from that one element is described by the producer as a 'high transpartent lens' which, most likely, means a lens made of high transmission glass. Inside you can also find a circular aperture with an impressive number of 14 diaphragm blades which can be closed down to a value of f/16 at the maximum. The producer also boasts of employing HD Nano Multilayer coatings.
Buyers get both caps, two hoods (one bigger, petal-type, and the other smaller, which allows you to screw an 82 mm filter inside) and a soft pouch in the box.
