http://www.kenrockwell.com/nikon/20mm-f18.htm
以下擷取重點部分簡略用成中文：
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.
如同大家所猜測的，這是顆完美無瑕的鏡頭，遠遠海放Nikon其他舊有的20mm，真不好玩
。若你在找大光圈、神銳利、神好用的超廣角定焦，這顆就是Nikon有史以來最適合的一
顆，拿一顆20.8加上28-300VR就可以直接包下任何的場景了。
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最銳利的超廣角定焦鏡，不只是比過去所有的Nikon超廣角或還是
變焦鏡頭鏡頭都還要快上一檔，而且還超級銳利(就算光圈全開)，神近的最短對焦距離（
12.5公分），再加上沒有鬼影、星芒很棒(超讚的14角星芒)、極低變形畸變。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).
這顆鏡頭神銳利、神快又輕巧小顆。自從1984首顆AIS 20 F2.8後，三十年來Nikon都沒更
新20mm超廣角的光學設計，此番20.8的推出絕對讓你看到Nikon 這三十年來的精粹，他讓
所有其他的20 F2.8鏡頭都顯得遜色，在大光圈全開下更是差異甚遠。
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!
超音波馬達
無光圈環
超低色散(2片超低色散玻璃)
N家奈米鍍膜(一面奈米水晶鍍膜抗耀光鬼影)
內對焦
非球面鏡(2片非球面鏡)
77mm
11組13片
Nikon多種混合鍍膜，使得耀光掰掰，想要耀光的話可能得選20F2.8D了
色彩方面則跟其他鏡頭無異
非常輕微的桶狀畸變
就算濾鏡很厚也沒暗角
就算在135片幅裝兩個濾鏡都沒暗角 OP
135片幅裝三個濾鏡有暗角(最短對焦距離下則無)
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.
在兩物體間來回對焦時，對焦距離愈短成像愈大(只有拍動作片需在乎)
在測試的D810上看不到橫向邊緣色散
大逆光底下有些微藍色色散，輕微到不令人擔心