Learn Swedish: Objektivet är bra, men bilden blir mörk såvida bländaren inte öppnas. - The lens is good, but the picture gets dark unless the aperture is opened.

Såvida introduces a subordinate clause. In Swedish subordinate clauses, a sentence adverb like inte always comes before the verb but after the subject. Here, the subject is bländaren, so the strict word order must be såvida bländaren inte öppnas.

What is the difference between using såvida ... inte and om ... inte here?

They both translate to the English word unless, but såvida is slightly more formal and places a stronger emphasis on the strict condition. You will often see it used in written instructions, rules, or technical explanations like this one about a camera lens.

Why does the verb öppnas end with an -s?

The -s creates the passive voice, indicating that the aperture is acted upon. It translates to is opened. Since the sentence focuses on the camera rather than who is physically opening the aperture, the s-passive is the most natural choice.

Why use blir instead of är when talking about the picture?

Blir means becomes or gets, which focuses on a change of state. If you used är, it would mean the picture is already inherently dark. Using blir emphasizes that the darkness is the direct consequence of the aperture remaining closed.