Photographic Depth of Field: Focus, Blur, and Computational Control

All flashcards

What is the circle of confusion?

The largest blur-spot diameter accepted as visually point-like under specified image and viewing conditions.

What is the object-field method?

A focusing approach that prioritizes recognizable detail in selected objects rather than equal sharpness at every depth.

What is focus sweep?

A method that moves the focal plane through a depth range during one exposure, producing blur for computational removal.

What is color apodization?

An optical method that gives color channels different effective apertures so processing can use sharper channel information.

How does diffraction limit stopping down?

A smaller aperture increases geometrical depth of field but can spread light and soften the whole image.

Quiz questions

1. When subject framing is kept constant, what generally happens to depth of field if focal length increases while the f-number stays the same?Answer: It stays nearly the same because the camera moves farther away.
2. What do tilt and swing movements change in a camera?Answer: The orientation of the plane of focus.
3. How does focus stacking create an image with greater apparent depth of field?Answer: It combines sharp regions from photographs focused at different distances.
4. What is the far depth-of-field limit when a camera is focused at the hyperfocal distance?Answer: Infinity, under the chosen circle-of-confusion criterion.
5. Why can a very high f-number reduce overall image sharpness?Answer: Diffraction spreads light at the smaller aperture.