Lens Optics and Selection Flashcards
7 cards from real Photography practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Lens Optics and Selection flashcards as text
What happens to depth of field as you move closer to your subject, assuming aperture and focal length remain constant?
Answer: Depth of field decreases
As subject distance decreases, depth of field decreases—at very close focusing distances like macro photography, depth of field can be just millimeters deep.
What does OIS (Optical Image Stabilization) do inside a lens?
Answer: Uses gyroscopic sensors and moving lens elements to counteract camera shake
OIS uses gyroscopic sensors to detect camera movement and shifts a floating lens element in the opposite direction to counteract handshake blur.
A 'fast' lens refers to one that:
Answer: Has a large maximum aperture (low f-number)
A 'fast' lens has a large maximum aperture (such as f/1.4 or f/1.8), allowing more light to reach the sensor in a given time, enabling faster shutter speeds in low light.
What is 'focus shift' in a lens?
Answer: A change in the point of focus when the aperture is stopped down from the focusing aperture
Focus shift occurs in some lenses when spherical aberration changes as the aperture is stopped down, causing the focused image to shift slightly from where it was composed.
What is the 'circle of confusion' in relation to depth of field?
Answer: The maximum acceptable blur spot diameter on the sensor for a point to be considered 'in focus'
The circle of confusion defines how large a blur spot can be while still appearing acceptably sharp; depth of field calculations are based on this threshold.
Which optical design reduces ghosting and flare in backlit situations?
Answer: Nano-crystal or multi-layer anti-reflective coatings
Multi-layer anti-reflective coatings (like Nikon's Nano Crystal Coat or Canon's ASC) reduce internal reflections between glass elements, minimizing ghosting and flare.
When would a photographer choose a 'decentering' test for their lens?
Answer: To determine whether the optical elements are perfectly aligned on the optical axis
A decentering test checks if lens elements are perfectly aligned; a decentered lens shows one corner or side sharper than the opposite side, which is a manufacturing defect.