MTF and Lens Design Quiz: Aberrations and Optical Quality

Learn to read MTF charts and understand lens design tradeoffs. This quiz covers field curvature, focus shift, decentering, and the optical factors that determine real-world lens performance beyond marketing specs.

Quiz 35: Lens Design, MTF, and Field Curvature in Practice

MTF describes:

Color space

Contrast transfer at different spatial frequencies

Shutter sync

ISO scaling

High MTF at low frequencies suggests:

Good overall contrast

Only fine detail

Worse bokeh

More distortion

High MTF at high frequencies suggests:

Better micro-detail resolution

Worse resolution

More noise

Less sharpness

Field curvature causes:

Flat plane of focus

Curved plane of focus, edges may focus at different distance than center

Only vignetting

Only distortion

A symptom of field curvature is:

Edges soft at same focus, but sharpen when refocusing slightly

Perfect corners always

More noise in corners

Better flash sync

Decentering often results in:

Uniform softness

One side/corner softer than others

Better bokeh

Better color

Coma is most problematic for:

Portraits

Stars near edges

Macro

Product shots

Longitudinal CA appears as:

Colored fringes in front/behind focus plane

Edge-only color fringing

Noise

Motion blur

Lateral CA is typically:

Focus-dependent

Edge-dependent and correctable by scaling channels

Only in center

Only in RAW

Stopping down reduces:

Lateral CA always

Longitudinal CA and improves aberrations (often)

Rolling shutter

Flicker

Focus shift refers to:

Exposure shift

Focus plane moving when stopping down

WB shift

Distortion shift

Focus breathing impacts:

Motion blur

Framing changes while focusing

ISO

Flash power

Lens profile corrections can fix:

Perspective parallax

Distortion and vignetting (and often lateral CA)

Missed focus

Subject motion

A lens with strong vignetting wide open:

Cannot be corrected

Often correctable in post or by stopping down

Changes ISO

Improves autofocus

Real world sharpness depends on:

Lens only

Sensor only

Lens, focus accuracy, shutter stability, processing

White balance only

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