Chapter 4 — Quiz

Twenty-four questions to check that the lens has stopped being a mystery. Mix of multiple choice, true/false (with a required justification — the reason is the real answer), short answer, and a few "what's wrong with this shot?" perception questions. Answer from memory first; the key and a topics-to-review map are at the end.

Multiple choice

1. A 50mm lens frames as a "normal" lens on a full-frame camera. On a camera with a 2× crop factor, that same 50mm lens frames most like:

• A) a 25mm wide lens
• B) a 50mm normal lens
• C) a 100mm short telephoto
• D) it doesn't change

2. Which aperture is the largest physical opening and lets in the most light?

• A) f/16
• B) f/8
• C) f/2.8
• D) f/1.8

3. You want to compress the background so it looms large behind a still subject ("alone in a crowd"). You should:

• A) use a wide lens and stand close
• B) use a long lens and stand far back
• C) use any lens and open the aperture
• D) use portrait mode

4. Which set of choices produces the shallowest depth of field?

• A) f/16, wide lens, subject far away
• B) f/1.8, long lens, subject close to camera
• C) f/8, normal lens, subject at middle distance
• D) f/5.6, wide lens, subject far away

5. "Bokeh" refers to:

• A) the amount of the scene that is in focus
• B) the aesthetic character of the out-of-focus areas
• C) the brightness of the image
• D) a type of zoom lens

6. On a typical smartphone, the sharpest, best-in-low-light lens to use as your default is:

• A) the ultra-wide
• B) the main "1x" lens
• C) whatever digital-zoom value crops nicely
• D) portrait mode

7. A focus pull (rack focus) is best described as:

• A) a way to zoom without a zoom lens
• B) changing focus during a shot to lead the viewer's eye from one plane to another
• C) an autofocus setting
• D) a lens cleaning technique

8. The single most useful manual-focus aid, which paints a coloured outline over whatever is in sharp focus, is:

• A) punch-in magnification
• B) zebras
• C) focus peaking
• D) the histogram

True / False (justify your answer — the justification is graded)

9. True or False: Perspective — how deep or compressed space looks — is created by the focal length of the lens.

10. True or False: Opening the aperture from f/8 to f/2 both lets in more light and deepens the depth of field.

11. True or False: A prime lens has one fixed focal length, so to change your framing you move the camera.

12. True or False: If you miss focus on set (the eyes come out soft), you can usually recover it by sharpening in the edit.

13. True or False: A phone's "portrait mode" uses a fast lens to physically throw the background out of focus.

14. True or False: Because this book quotes focal lengths as "full-frame-equivalent," a 35mm-equivalent look is the same framing regardless of what sensor your camera has.

Short answer

15. In one or two sentences, explain why the f-stop scale runs "backwards" — why a bigger number means a smaller opening.

16. Name the three levers that make depth of field shallower, and say which one costs you nothing but a step.

17. Give the emotional default — in a few words each — for a wide lens, a normal lens, and a long lens. (What relationship does each set up between viewer and subject?)

18. Why does this book insist you decide depth of field on set rather than "in post"? Give the specific reason.

19. A reader has a phone and no budget and wants a "cinematic" shallow-depth talking-head. Give them two honest ways to get real background separation from a phone's optics (not portrait mode).

20. Explain the difference between focal length and shot size, and why a "close-up" can be shot two very different ways.

What's wrong with this shot? (perception)

21. A vlogger films a talking-head selfie on their phone's ultra-wide lens held at arm's length, very close to their face. Viewers say they look "weird." Name the optical problem and the fix.

22. An interview is shot at f/1.4 for maximum background blur. In the footage, the subject's eyes drift in and out of sharpness every time they lean forward to make a point. Diagnose the cause and give two fixes.

23. A shooter wants a slow, dramatic move toward a subject, so they slowly turn the zoom ring in during the take. It looks cheap and flat. Why — and what should they have done instead?

24. A product shot for a client is filmed on a long lens wide open; the front of the product glows beautifully but the back third is an unreadable blur, and the client needs the whole label visible. What went wrong and how do you reshoot it?

More short answer

25. The chapter's title claims "the lens beats the body." In one or two sentences, explain why the lens shapes the image more than the camera body does.

26. You are shooting a walk-and-talk with a moving subject, working solo. Give a starting focal length range, aperture, and focus approach, and justify each in terms of the shot's demands.

27. True or False (justify): "A prime lens is simply better than a zoom lens."

28. What's wrong with this shot? A creator films a "cinematic" clip using their phone's "5x" setting, which sits between the phone's main and telephoto lenses. The image looks soft and mushy compared to their other clips. Diagnose it and give the fix.

Answer Key

1. C. A 2× crop factor makes any lens frame like twice its number on full-frame: 50mm × 2 = 100mm-equivalent, a short telephoto. (§4.1; Ch. 2 crop factor.)

2. D. f/1.8 — the smallest f-number is the biggest opening and the most light. The scale is a ratio, so it runs "backwards." (§4.2, FIGURE 4.3.)

3. B. Long lens, far back. Compression is a product of shooting from a distance; the long lens is what lets you fill the frame from there. Perspective is distance, not lens. (§4.1, FIGURE 4.1–4.2.)

4. B. f/1.8 (open), long lens, subject close — all three shallow-depth levers pulled at once. (§4.3, FIGURE 4.4.)

5. B. The character of the out-of-focus rendering — creamy vs. busy, round vs. edgy — not merely the presence of blur. (§4.3.)

6. B. The main "1x" lens: biggest sensor, sharpest optics, best low light. In-between digital-zoom values just crop and enlarge it. (§4.4, FIGURE 4.6.)

7. B. Changing focus during a shot to carry the eye between planes — "a cut you don't have to make." (§4.5, FIGURE 4.7.)

8. C. Focus peaking — a coloured outline over the sharp plane, so you can watch focus land on the eyes. (§4.5.)

9. False. Perspective is created by camera-to-subject distance, not focal length. The lens only sets how much fits in frame (angle of view); standing close opens space, standing far compresses it. The lens matters only because it dictates how far you must stand for a given framing. (§4.1 — the chapter's central threshold concept.)

10. False. Opening up lets in more light but makes depth of field shallower, not deeper. Light and focus move together, and opening the aperture always thins the zone of sharpness. (§4.2–4.3.)

11. True. A prime is a single fixed focal length; you reframe by moving the camera — which is secretly good discipline, because it forces you to commit to a perspective. (§4.4.)

12. False. Missed focus is one of the few things the edit cannot fix — the sharp detail was never recorded, and "sharpening" a soft shot only produces crunchy artefacts. Decide and confirm focus on set. (§4.3 ✂️; §4.5.)

13. False. A phone's small sensor and short actual focal length give it naturally deep focus; portrait mode computes a synthetic blur in software, which is why it fails at edges like hair and glasses. (§4.4.)

14. True. That is the entire point of quoting equivalents — a 35mm-equivalent gives the same field of view on any sensor, because the equivalent already accounts for the crop factor. (§4.1; Ch. 2.)

15. Because the f-number is a ratio (focal length divided by the diameter of the opening), so a larger denominator — a smaller hole — yields a larger number. You steer by the effect, not the arithmetic: small number = big hole = more light and shallower focus. (§4.2; 🔬 The Tech.)

16. (1) Open the aperture (smaller f-number), (2) use a longer focal length, (3) get the subject closer to the lens (and farther from the background). The third — stepping closer / moving the background away — costs nothing. (§4.3.)

17. Wide = involvement / "you are here" (viewer inside the scene, subjective, open space). Normal = honesty / "as the eye sees" (neutral, believable). Long = observation / isolation (viewer watching from a distance, objective or heightened, compressed space). (§4.1.)

18. Because focus is one of the few things post genuinely cannot change: you cannot refocus a shot that was shot soft, and you cannot cleanly re-blur a deep-focus shot without imperfect effects work. Unlike colour or level, the focus information is fixed in the file at capture. (§4.3 ✂️.)

19. (1) Move the subject far from the background and get close to them with the main or telephoto lens — real optics will give some genuine falloff. (2) Use the phone's telephoto (longer) lens rather than the wide one, since longer focal lengths shallow the depth. (Bonus: shoot toward a background with point-lights for visible bokeh.) (§4.3–4.4.)

20. Focal length is how wide or long the lens is (and what the background does); shot size is how big the subject is in the frame as a deliberate compositional choice (wide/medium/close-up — the Chapter 7 system). A close-up can be a wide lens up close (deep, distorted, immersive) or a long lens far back (compressed, flattering, isolated) — same subject size, opposite feel. (§4.1; 🔗 Ch. 7.)

21. The ultra-wide lens up close exaggerates near features — nose and forehead balloon — and bends the frame edges; wide lenses are unflattering on faces at close range. Fix: switch to the main or telephoto lens and step back to fill the frame from farther away, which flattens and flatters the face. (§4.1, §4.4; Ex. 25.)

22. At f/1.4 the depth of field is so thin that leaning forward moves the eyes out of the sharp plane. Fixes: (1) stop down to f/2.8–f/4 for more focus margin; (2) use continuous eye-detect autofocus, or a focus puller / rehearsed marks, to hold the eyes as the subject moves. (§4.3 ⚠️; §4.5.)

23. A zoom-in changes magnification but not perspective, so the eye reads it as flat and artificial — "home video." A physical push-in (moving the whole camera) shifts perspective as it travels and looks alive. Move the camera, not the ring. (§4.4 ⚠️; 🔗 Ch. 8.)

24. Shot too wide open: the depth of field is thinner than the product is deep, so only the front plane is sharp. Reshoot stopped down (toward f/8), and if needed step back with a slightly longer lens or angle the product so its depth sits within the focus zone. Sharpening in post cannot recover unrecorded detail. (§4.3; Ex. 27.)

25. The body records the image, but the lens forms it — the lens decides the focal length (and therefore the perspective and the viewer's relationship to the subject), the aperture (and therefore the depth of field and where the eye goes), and much of the sharpness and character (bokeh). Two bodies with the same lens look far more alike than two lenses on the same body. The eye that sees matters more than the box that records. (Chapter premise; §4.1–4.3.)

26. Start around 24–35mm-equiv (wide enough to keep a moving subject in frame and give a sense of "you are here"), at about f/4–f/5.6 (enough depth-of-field margin that the subject staying sharp doesn't depend on perfect focus as they move), with eye-detect autofocus (a solo operator can't ride focus by hand while moving) — tested first for hunting. Each choice is driven by movement: wider frames a mover, deeper focus forgives their motion, autofocus frees your hands. (§4.6 Settings Box; §4.5.)

27. False. Each trades something real: a prime is usually sharper, faster, lighter, and cheaper at a given quality, and its single focal length is good discipline; a zoom buys flexibility and speed when you can't move (events, wildlife, run-and-gun). "Better" depends on the job — most working shooters own both. (§4.4.)

28. The "5x" value sits between the phone's two real lenses, so the phone is digitally zooming — cropping and enlarging the main sensor's image and throwing away resolution, which is why it looks soft and mushy. Fix: shoot on the actual named lenses (main or telephoto) and get the framing with your feet, or accept the main lens's full quality and crop deliberately in the edit if you must. Treat the phone's marked lenses as primes and avoid the fake in-between values. (§4.4, FIGURE 4.6.)

Topics to review by question

• The lens vs. the body / chapter premise: 25 → Overview, §4.1–4.3.
• Focal length, perspective, crop/equivalent: 1, 3, 9, 14, 17, 20, 21 → §4.1 (and Ch. 2 crop factor).
• Aperture and the f-stop: 2, 10, 15 → §4.2.
• Depth of field and bokeh: 4, 5, 16, 18, 22, 24 → §4.3.
• Prime, zoom, and the phone's lenses: 6, 11, 13, 19, 23, 27, 28 → §4.4.
• Focus for video / focus pulls: 7, 8, 12 → §4.5.
• Choosing the lens for the shot: 26 → §4.6.

If you missed more than one in any group, reread that section and, more importantly, shoot the exercise attached to it — the lens is learned in the hands.