To isolate a subject from its surroundings, you should use a lens opening such as f...

• A. 22
• B. 8
• C. 2.8
• D. 5.6

Answer: (C)

Isolating a subject from its surroundings hinges on creating a shallow depth of field, which makes the background appear blurred while the subject stays sharp. The aperture controls depth of field: a wider opening (smaller f-number) lets in more light and produces a blurrier background, helping the subject stand out. Among the given openings, f/2.8 is wide enough to produce noticeable background blur, making it the best choice for isolation. The larger numbers correspond to smaller openings (f/22 being very deep, f/8 and f/5.6 offering progressively more of the scene in focus), which reduce isolation by keeping more of the surroundings sharp.