Photography Lens Optics and Selection 2 — Questions and Answers
Question 1: What does the term 'bokeh' refer to in photography?
- The overall sharpness of an image
- The aesthetic quality of the out-of-focus blur (Correct answer)
- The distortion caused by wide-angle lenses
- The chromatic fringing around bright objects
Correct answer: The aesthetic quality of the out-of-focus blur
Bokeh describes the visual quality of the out-of-focus areas in an image, determined by the lens's optical design and aperture shape.
Question 2: A photographer needs to shoot wildlife from 100 feet away. Which focal length is MOST appropriate?
- 24mm
- 50mm
- 85mm
- 400mm (Correct answer)
Correct answer: 400mm
A 400mm telephoto lens provides the reach needed to capture distant wildlife without disturbing the animals.
Question 3: What is 'focus breathing' in a lens?
- The lens fogging up due to temperature changes
- A change in the apparent focal length as focus distance changes (Correct answer)
- The audible sound of autofocus motors
- Vibration caused by image stabilization
Correct answer: A change in the apparent focal length as focus distance changes
Focus breathing is the unintended change in a lens's angle of view as it racks through its focus range, which is particularly problematic for video work.
Question 4: Which aperture value provides the WIDEST depth of field?
- f/1.4
- f/2.8
- f/8
- f/16 (Correct answer)
Correct answer: f/16
f/16 is a small aperture that allows more of the scene to appear in focus, creating a wide depth of field.
Question 5: What is a 'prime' lens?
- A lens with the highest quality optical elements available
- A lens with a fixed focal length (Correct answer)
- The first lens released in a manufacturer's lineup
- A lens optimized for professional use only
Correct answer: A lens with a fixed focal length
A prime lens has a single fixed focal length, as opposed to a zoom lens that covers a range of focal lengths.
Question 6: Chromatic aberration appears in photographs as:
- Dark vignetting in image corners
- Color fringing along high-contrast edges (Correct answer)
- Overall softness across the image
- Repetitive ghost patterns from bright lights
Correct answer: Color fringing along high-contrast edges
Chromatic aberration occurs when a lens fails to focus all wavelengths of light at the same point, causing colored fringing—often purple or green—along high-contrast edges.
Question 7: What does 'IF' (Internal Focusing) mean in lens design?
- The lens uses a fluorite element internally
- The lens does not change length when focusing (Correct answer)
- The front element rotates during focusing
- The lens is designed for infrared photography
Correct answer: The lens does not change length when focusing
Internal focusing lenses adjust focus by moving internal elements, so the physical length of the lens and front element position remain constant.
Photography Lens Optics and Selection 2
What does the term 'bokeh' refer to in photography?