Photography Lens Optics and Selection 4

Question 1

What is 'spherical aberration' and how does it affect image quality?

Accepted Answer

Light rays passing through lens edges focus at a different point than those through the center, causing softness

Answer

Spherical aberration occurs because curved lens surfaces cannot focus all incoming rays to a single point, resulting in reduced sharpness and contrast, especially at wide apertures.

Question 2

An 85mm lens on a crop sensor camera with a 1.5x crop factor has an equivalent focal length of:

Accepted Answer

127.5mm

Answer

Multiplying 85mm by the 1.5x crop factor gives an equivalent full-frame field of view of 127.5mm.

Question 3

What is the primary purpose of a lens hood?

Accepted Answer

To reduce flare by blocking stray light from entering the lens at oblique angles

Answer

A lens hood blocks stray light from outside the frame from hitting the front element at angles that cause flare and reduce contrast.

Question 4

What does 'field curvature' mean as a lens aberration?

Accepted Answer

The inability of a lens to focus on objects at the edges of the frame simultaneously with the center

Answer

Field curvature means the plane of sharp focus is curved rather than flat, so when the center of an image is sharp, the corners may be out of focus and vice versa.

Question 5

Which lens mount characteristic allows a lens to be adapted to multiple camera systems?

Accepted Answer

The rear flange distance (flange focal distance)

Answer

A shorter flange focal distance on a camera body (common in mirrorless systems) allows adapters to be used for lenses with longer flange distances from other systems.

Photography Practice Test

Photography Practice Test

Photography Lens Optics and Selection 4