http://www.kenrockwell.com/nikon/20mm-f18.htm
以下撷取重点部分简略用成中文：
As you may have guessed, this is a flawless lens. It is so far ahead of
Nikon's old 20mm lenses that it's not funny.
If you want a super-fast, super-sharp, super easy to use ultra-wide lens,
this is the best Nikon has ever made.
Grab one of these and the 28-300mm VR and you're prepared for anything.
如同大家所猜测的，这是颗完美无瑕的镜头，远远海放Nikon其他旧有的20mm，真不好玩
。若你在找大光圈、神锐利、神好用的超广角定焦，这颗就是Nikon有史以来最适合的一
颗，拿一颗20.8加上28-300VR就可以直接包下任何的场景了。
This new Nikon 20mm f/1.8 FX is Nikon's sharpest fixed ultrawide lens. Not
only is it over a stop faster than any previous Nikon ultrawide lens or zoom,
it's ultrasharp (even wide-open), it focuses super-close, has no ghosts, has
great sunstars and only minimal distortion.
新的Nikon 20.8是Nikon最锐利的超广角定焦镜，不只是比过去所有的Nikon超广角或还是
变焦镜头镜头都还要快上一档，而且还超级锐利(就算光圈全开)，神近的最短对焦距离（
12.5公分），再加上没有鬼影、星芒很棒(超赞的14角星芒)、极低变形畸变。ꀊIt's ultrasharp, ultrafast, and small and light. Nikon hasn't updated the
optical design of its other 20mm ultrawide lens in over 30 years since the
original 20/2.8 AI-s lens of 1984, so this new 20/1.8 is a real eye opener in
what Nikon has learned in 30 years. This new lens makes any old 20/2.8 look
broken by comparison, especially at large apertures (the AF, AF-D and AI-s
lenses all have the same optical design).
这颗镜头神锐利、神快又轻巧小颗。自从1984首颗AIS 20 F2.8后，三十年来Nikon都没更
新20mm超广角的光学设计，此番20.8的推出绝对让你看到Nikon 这三十年来的精粹，他让
所有其他的20 F2.8镜头都显得逊色，在大光圈全开下更是差异甚远。
AF-S and SWM: Silent Wave Autofocus Motor.
G: Gelded for cost-reduction and removing compatibility with older cameras.
ED: Magic Extra-low Dispersion glass for reduced secondary chromatic
aberration.
N: Magic Nano-crystal coating, meaning a coating which varies its index of
refraction continuously to achieve even greater reflection reduction. It's
probably only on one surface, and is used mostly for marketing purposes.
RF: Rear focusing; nothing moves externally as focused except the rear
element.
Aspherical: Specially curved glass to give even sharper pictures.
7: 77mm filter O涏m
13 elements in 11 groups.
2 are of ED glass.
2 are aspherical.
One surface, usually the inside rear of the largest element, is Nano-crystal
coated to eliminate ghosts.
It's multicoated, which Nikon calls Nikon Super Integrated Coating.
With the Nano coating, there are no ghosts. If you want little colored blobs
in the image from the sun, use the old 20/2.8 AF-D instead.
The color rendition is the same as my other Nikkor AF lenses.
The Nikon 20mm f/1.8 AF-S has very mild barrel distortion.
There is no problem with vignetting, even with combinations of thick filters.
On full-frame I can shoot with two stacked filters with no vignetting.
With three stacked filters on full frame I get vignetting — but not at the
closest focus distances!
超音波马达
无光圈环
超低色散(2片超低色散玻璃)
N家奈米镀膜(一面奈米水晶镀膜抗耀光鬼影)
内对焦
非球面镜(2片非球面镜)
77mm
11组13片
Nikon多种混合镀膜，使得耀光掰掰，想要耀光的话可能得选20F2.8D了
色彩方面则跟其他镜头无异
非常轻微的桶状畸变
就算滤镜很厚也没暗角
就算在135片幅装两个滤镜都没暗角 OP
135片幅装三个滤镜有暗角(最短对焦距离下则无)
Of interest mostly to cinematographers focusing back and forth between two
subjects, the image from the Nikon 20mm f/1.8 AF-S gets larger as focused
more closely.
There are no lateral color fringes on the D810, which corrects any
automatically.
If you push it shooting into the light, there are some very slight blue
fringes, but not anything to worry about.
在两物体间来回对焦时，对焦距离愈短成像愈大(只有拍动作片需在乎)
在测试的D810上看不到横向边缘色散
大逆光底下有些微蓝色色散，轻微到不令人担心