Style manuals often ignore the problem of length, offering little advice about making things shorter as well as clearer. But space, or the lack of it, is frequently the biggest problem that the writer has to deal with.
In children’s books, for example, of which I have written a few, word counts are sometimes strictly limited because the words have to fit round pictures whose size and position have already been fixed by a designer.
One gets cunning at shortening sentences without losing their meaning. An apparently short and direct sentence like
A camera has a lens that makes an image.
can be made even shorter by using the possessive case to remove both a verb and a subordinate clause:
A camera’s lens makes an image.
or shorter still by using the fact that in English you are allowed to turn almost any noun into an adjective:
A camera lens makes an image.
These changes have reduced 40 characters to 29 with very little loss of meaning. It’s true that the lens, not the camera, is now the subject of the sentence, but this makes little difference in practice when there is an accompanying image.
Tricks like this can make the difference between saying what you want to say or having to change the whole thing and say something different.