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9 Questions

What is depth of field (DOF)?

Which factor does not affect the DOF?

What happens to the DOF when the aperture size is increased?

What happens to the DOF when the sensor size is decreased?

What is the generally accepted size of the acceptable circle of confusion?

What is focus stacking?

What is the hyperfocal distance?

What is the depth of field for a lens focused at the hyperfocal distance?

What is the effect of diffraction on DOF?


Depth of Field: Factors and Effects

  • Depth of field (DOF) is the distance between the nearest and the furthest objects that are in acceptably sharp focus in an image captured with a camera.

  • The DOF can be determined by focal length, distance to subject, the acceptable circle of confusion size, and aperture.

  • Increasing the size of the aperture or increasing the focal length reduces the depth of field.

  • Sensor size affects DOF in counterintuitive ways: decreasing the size of the sensor while holding focal length and aperture constant will decrease the DOF (by the crop factor).

  • Precise focus is only possible at an exact distance from the lens.

  • The acceptable circle of confusion is generally accepted as 0.25 mm for an image viewed from 25 cm away.

  • Camera movements such as swivel and shift adjustments of the lens holder and the film holder can cause the plane of focus (POF) to swivel.

  • Focus stacking combines multiple images focused on different planes, resulting in an image with a greater (or less, if so desired) apparent depth of field than any of the individual source images.

  • Diffraction causes images to lose sharpness at high F-numbers, and hence limits the potential depth of field.

  • Many lenses include scales that indicate the DOF for a given focus distance and f-number.

  • The DOF beyond the subject is always greater than the DOF in front of the subject.

  • For given near and far DOF limits, focus and f-number can be obtained through simple calculations.Understanding Depth of Field in Photography

  • The f-number is smallest when focus is set to the harmonic mean of the near and far distances.

  • In practice, this is equivalent to the arithmetic mean for shallow depths of field.

  • The focus spread is the difference between the near and far distances.

  • The blur disk diameter of a detail at distance x from the subject can be expressed as a function of the subject magnification, focal length, f-number, or the aperture.

  • The blur increases with the distance from the subject.

  • When the blur disk diameter is less than the circle of confusion, the detail is within the depth of field.

  • The depth of field is shallower for wider apertures and longer focal lengths.

  • The depth of field is deeper for smaller apertures and shorter focal lengths.

  • The hyperfocal distance is the closest distance at which a lens can be focused while keeping everything beyond that point acceptably sharp.

  • The depth of field extends from half the hyperfocal distance to infinity.

  • The depth of field can be calculated using various online calculators or smartphone apps.

  • The depth of field can be used creatively to isolate the subject or to keep everything in focus.


How much do you know about depth of field in photography? This quiz will test your understanding of the factors and effects that contribute to the depth of field in an image. From aperture and focal length to the acceptable circle of confusion and sensor size, this quiz covers it all. Test your knowledge and learn more about how to use depth of field creatively in your photography.

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