Quoting Calvino's memo on Exactitude:

"To my mind, exactitude means three things above all:

1) a well-defined and well-calculated plan for the work in question;

2) an evocation of clear, incisive, memorable visual images; in Italian we have an adjective that doesn't exist in English, "icastico," from the Greek;

3) a language as precise as possible both in choice of words and in expression of the subtleties of thought and imagination."

To illustrate this further and to stretch the continuum from exactitude to subtelty, Calvino uses the Italian word and idea, il vago, which while meaning vague in definition also means lovely and attractive. He then cites Leopardi who addresses il vago in his poem Zibaldone. After re-reading the poem, Calvino says of the poet Leopardi:

"What he requires is an exact and meticulous attention to the composition of each image, to the minute definition of details, to the choice of objects, to the lighting and the atmosphere, all in order to attain the desired degree of vagueness."(!)

And "....the poet of vagueness can only be the poet of exactitude..."

There's also this - Calvino quoting Douglas Hofstadter - which relates to the above though it's from the memo on Visibility:

"Think, for instance, of a writer who is trying to convey certain ideas which to him are contained in mental images. He isn't quite sure how those images fit together in his mind, and he experiments around, expressing things first one way and then another, and finally settles on some version. But does he know where it all came from? Only in a vague sense. Much of the source, like an iceberg, is deep underwater, unseen - and he knows that."