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Hi teachers, the following sentence makes me really confused.

The lens is of universal focus, down to any distance accommodated by the unaided eye, simply because it is of short focal length.

Why can't I just say,

The lens is universal focus, down to any distance accommodated by the unaided eye, simply because it is short focal length.

Thanks in advance

Henry
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Hi Henry,

The lens is of universal focus, down to any distance accommodated by the unaided eye, simply because it is of short focal length.

Why can't I just say,

The lens is universal focus, down to any distance accommodated by the unaided eye, simply because it is short focal length.


of universal focus describes a quality of the lens. Think of The lens is of universal focus as a shortened form of The lens is a lens of universal focus. In effect, you are just omitting a lens.

You can't say a lens is . . . length because it isn't, a lens is a lens.

Best wishes, Clive

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"is of" has several meanings. In this case, "is of" is used to mean "has".

Compare:

The lens is of short focal length.

The United Nations is of the view that the elections were fair.

What is perhaps weird is that these expressions can often be rephrased with the subject of the sentence as the object of the preposition "of" without changing the meaning.

The focal length of the lens is short.

The view of the United Nations is that the elections were fair.

CJ