twenty-twenty

英訳された宮部みゆきの小説は江戸川区図書館に5冊あるのですが、これまでに "Devil's Wisper", "Shadow Family", "Crossfire", "All She Was Worth" を読んだので、これから読む "The Sleeping Dragon" が最後になります。
今日取り上げる表現はそのPROLOGUEからです。
This is the record of a battle.
Right off the bat, though, I need to make it clear that I was never on the front line. The heroes were two young men just past adlescence.
One I knew well, and the other I came to know well enough to be sure that he wouldn't mind me telling you what happened. If I had met him sooner, I might have been able to do something to actually stop the chain of events that occurred. But hindsight is always twenty-twenty.
"twenty-twenty" は視力が正常なことを示していて、米国の眼鏡屋で "20/20" を含んだ掲示を見た覚えがあります。

・Oxford English Dictionary: Denoting vision of normal sharpness.: I guess my twenty-twenty eyesight went out with the lights.

・Collins Dictionary: being of normal acuity: usually written 20/20: With twenty-twenty hindsight I realise that I too should have leapt off the chair at that point and no damage would have been done.
・Merriam-Webster's Online Dictionary: marked by facilely accurate discernment, judgment, or assessment: hindsight is twenty-twenty
当然の事ながら、判断力、評価力、洞察などは、"hindsight" と一緒に使われれば、優れているのは当たりまえですね。