Factors Affecting Depth of Field
Several other factors, such as subject matter, movement, camera-to-subject distance, lens focal length, selected lens f-number, format size, and circle of confusion criterion also influence when a given defocus becomes noticeable. The combination of focal length, subject distance, and format size defines magnification at the film / sensor plane.
DOF is determined by subject magnification at the film / sensor plane and the selected lens aperture or f-number. For a given f-number, increasing the magnification, either by moving closer to the subject or using a lens of greater focal length, decreases the DOF; decreasing magnification increases DOF. For a given subject magnification, increasing the f-number (decreasing the aperture diameter) increases the DOF; decreasing f-number decreases DOF.
If the original image is enlarged to make the final image, the circle of confusion in the original image must be smaller than that in the final image by the ratio of enlargement. Cropping an image and enlarging to the same size final image as an uncropped image taken under the same conditions is equivalent to using a smaller format under the same conditions, so the cropped image has less DOF. (Stroebel 1976, 134, 136–37).
When focus is set to the hyperfocal distance, the DOF extends from half the hyperfocal distance to infinity, and the DOF is the largest possible for a given f-number.
Read more about this topic: Depth Of Field
Famous quotes containing the words factors, affecting, depth and/or field:
“Girls tend to attribute their failures to factors such as lack of ability, while boys tend to attribute failure to specific factors, including teachers’ attitudes. Moreover, girls avoid situations in which failure is likely, whereas boys approach such situations as a challenge, indicating that failure differentially affects self-esteem.”
—Michael Lewis (late–20th-century)
“Children must eventually train their own children, and any impoverishment of their impulse life, for the sake of avoiding friction, must be considered a possible liability affecting more than one lifetime”
—Erik H. Erikson (20th century)
“It is thus that the few rare lucid well-disposed people who have had to struggle on the earth find themselves at certain hours of the day or night in the depth of certain authentic and waking nightmare states, surrounded by the formidable suction, the formidable tentacular oppression of a kind of civic magic which will soon be seen appearing openly in social behavior.”
—Antonin Artaud (1896–1948)
““My mother thinks us long away;
‘Tis time the field were mown.
She had two sons at rising day,
To-night she’ll be alone.”
—A.E. (Alfred Edward)