Здравствуйте, Ops, Вы писали:

Ops>Это в децибеллах, или почему такая шкала?

Имперские единицы измерения, однако.

Visual Acuity: What is 20/20 Vision?

20/20 vision is a term used to express normal visual acuity (the clarity or sharpness of vision) measured at a distance of 20 feet. If you have 20/20 vision, you can see clearly at 20 feet what should normally be seen at that distance. If you have 20/100 vision, it means that you must be as close as 20 feet to see what a person with normal vision can see at 100 feet.

Having 20/20 vision does not necessarily mean you have perfect vision. 20/20 vision only indicates the sharpness or clarity of vision at a distance. Other important vision skills, including peripheral awareness or side vision, eye coordination, depth perception, focusing ability and color vision, contribute to your overall visual ability.

Человек со стопроцентным зрением должен четко видеть каждым глазом некие объекты (символы в таблице для проверки зрения?) на расстоянии 20 футов (примерно 6 м).

Здравствуйте, Ops, Вы писали:

Ops>Это в децибеллах, или почему такая шкала?

Имперские единицы измерения, однако.

Visual Acuity: What is 20/20 Vision?

20/20 vision is a term used to express normal visual acuity (the clarity or sharpness of vision) measured at a distance of 20 feet. If you have 20/20 vision, you can see clearly at 20 feet what should normally be seen at that distance. If you have 20/100 vision, it means that you must be as close as 20 feet to see what a person with normal vision can see at 100 feet.

Having 20/20 vision does not necessarily mean you have perfect vision. 20/20 vision only indicates the sharpness or clarity of vision at a distance. Other important vision skills, including peripheral awareness or side vision, eye coordination, depth perception, focusing ability and color vision, contribute to your overall visual ability.

Человек со стопроцентным зрением должен четко видеть каждым глазом некие объекты (символы в таблице для проверки зрения?) на расстоянии 20 футов (примерно 6 м).

P.S. Строго говоря, на письме 20:20 — это не то же, что 20/20.