How aperture affects depth of field when using lens tilt
Asked 8/11/2012
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2 answers
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I understand that tilting a tilt-shift lens changes the plane of focus, so the in-focus region can look very different from a normal lens. For example, with about 8° of tilt, one side of the image can fall out of focus while a narrow band remains sharp.
How does aperture interact with that tilt effect? Does a wider aperture make the effect of a given tilt angle stronger, or does tilt only change the orientation of the focus plane while aperture still controls depth of field in the usual way? A simple explanation is preferred.
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
14y ago
2 Answers
7
Changing aperture has the same overall effect on depth-of-field with a tilted lens that it has on an untilted lens.
Tilting a lens changes the visible consequences of any change in aperture because it (when viewed sideways) changes the shape of the in-focus area from a rectangle to a wedge (with the point towards and above or below the camera, depending on tilt direction). The diagrams on this page include some good visualisations of the effect.
decreasing/increasing the aperture (increasing/decreasing f-number) effectively causes the width of the base of the wedge to increase/decrease accordingly. This results in the effect of the change in aperture becoming progressively smaller close to the point.
Originally by user9646. Source · Licensed CC BY-SA 4.0
user9646
14y ago
0
Generated from our catalog & community — verify before relying on it.
Aperture and tilt are related, but they do different jobs.
Tilt changes the orientation of the plane of focus. Instead of the sharp area being roughly parallel to the sensor, it becomes angled. In a side view, the in-focus region is often described as a wedge rather than a flat slab.
Aperture still affects depth of field in the normal way:
- wider aperture (smaller f-number) = shallower depth of field
- smaller aperture (larger f-number) = deeper depth of field
With tilt applied, changing aperture does not make the tilt angle itself “stronger.” An 8° tilt is still 8°. What changes is the thickness of the sharp region around that tilted plane.
So with a wider aperture, the wedge of acceptable focus becomes thinner. With a smaller aperture, it becomes thicker. The visual effect can seem unusual because the sharp zone is angled, but aperture is still just controlling how much depth of field you get around that tilted focus plane.
In short: tilt sets where the focus plane goes; aperture sets how thick the in-focus zone is around it.
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UniqueBot
AI14y ago
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