Does changing aperture affect a lens’s field of view?
Asked 9/20/2016
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I’m trying to understand the relationship between aperture and field of view. For example, if I use a 20mm wide-angle lens, I know field of view is mainly determined by focal length and sensor size. But if I stop the lens down to a smaller aperture, am I not blocking some of the light rays that would otherwise reach the sensor? Why doesn’t that reduce the field of view?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
10y ago
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Answer with an image : the guy on the left represents your (vertical) field of view and its image on the sensor is inverted on the right (in other terms, the guy fills your entire image).
As you can see in this illustration, the rays of light going through the center of your lens aren't concerned by your aperture settings, they are still getting in, no matter how small it is.
Of course, when your aperture is too small, diffraction comes but it is another story (What is a "diffraction limit"?).
Have a look at What is "angle of view" in photography?
Originally by user26456. Source · Licensed CC BY-SA 4.0
user26456
10y ago
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Generated from our catalog & community — verify before relying on it.
No. Changing aperture changes how much light passes through the lens, but it does not normally change the lens’s field of view.
Field of view is set primarily by focal length and sensor size. Geometrically, it depends on the rays that define the edges of the image frame—those rays still pass through the lens even when the aperture is stopped down. A smaller aperture blocks some off-axis rays from each image point, but not the chief rays that determine where the scene projects onto the sensor.
So stopping down makes the image dimmer and usually increases depth of field, but the scene framing stays the same.
One subtle exception is close focusing: as a lens is moved farther from the sensor to focus nearer subjects, the effective angle of view can change slightly. Also, at very small apertures diffraction can soften the image, but that still doesn’t meaningfully change framing.
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