Photography FREE Photography Lens Optics and Selection Questions and Answers 2 — Questions and Answers
Question 1: What does the term 'chromatic aberration' refer to in lens optics?
- Color fringing caused by a lens failing to focus all wavelengths to the same point (Correct answer)
- Barrel distortion at wide focal lengths
- Loss of sharpness due to diffraction at small apertures
- Vignetting in the corners of an image
Correct answer: Color fringing caused by a lens failing to focus all wavelengths to the same point
Chromatic aberration occurs when a lens cannot converge different wavelengths of light to a single focal point, producing color fringes along high-contrast edges.
Question 2: Which lens type is best suited for compressing the apparent distance between foreground and background elements?
- Telephoto lens (Correct answer)
- Wide-angle lens
- Fisheye lens
- Macro lens
Correct answer: Telephoto lens
Telephoto lenses compress perspective, making distant objects appear closer together and closer to the foreground subject.
Question 3: What is the primary advantage of an aspherical lens element?
- It corrects spherical aberration more effectively than a standard spherical element (Correct answer)
- It increases the maximum aperture of the lens
- It eliminates the need for image stabilization
- It reduces the weight of the lens by half
Correct answer: It corrects spherical aberration more effectively than a standard spherical element
Aspherical elements have a non-uniform curvature that corrects spherical aberration, which causes light rays hitting the edge of a lens to focus differently than those hitting the center.
Question 4: A photographer needs a lens with a constant maximum aperture of f/2.8 across a zoom range of 70-200mm. What type of lens construction achieves this?
- Internal zoom with a complex multi-group optical design (Correct answer)
- Variable aperture with a single moving element
- Fixed-body prime lens construction
- Retrofocus wide-angle design
Correct answer: Internal zoom with a complex multi-group optical design
Constant-aperture zoom lenses use complex internal zoom mechanisms with multiple lens groups that maintain the same maximum aperture throughout the entire focal range.
Question 5: What effect does a lens with a large number of rounded aperture blades have on out-of-focus highlights?
- It produces smoother, more circular bokeh (Correct answer)
- It creates harsh polygonal shapes in the bokeh
- It eliminates bokeh entirely
- It increases depth of field at all apertures
Correct answer: It produces smoother, more circular bokeh
More rounded aperture blades create a more circular opening, which renders out-of-focus highlights as smooth, round discs rather than harsh polygonal shapes.
Question 6: What is 'focus breathing' in a lens, and when is it most problematic?
- A shift in focal length when changing focus distance, most problematic in video work (Correct answer)
- A mechanical vibration in the autofocus motor during continuous shooting
- Air movement inside the lens barrel in cold weather
- The sound produced by ultrasonic focus motors
Correct answer: A shift in focal length when changing focus distance, most problematic in video work
Focus breathing is the change in apparent focal length as a lens shifts focus from near to far or vice versa, causing a zoom-like effect that is especially distracting in video footage.
Photography FREE Photography Lens Optics and Selection Questions and Answers 2
What does the term 'chromatic aberration' refer to in lens optics?