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🔋college physics i – introduction review

Pinhole Camera

Written by the Fiveable Content Team • Last updated September 2025
Written by the Fiveable Content Team • Last updated September 2025

Definition

A pinhole camera is a simple camera without a lens, using a small aperture to project an image onto a light-sensitive surface. It relies on the principles of optics and the ray aspect of light to create an inverted, real image of the scene in front of it.

5 Must Know Facts For Your Next Test

  1. The smaller the pinhole, the sharper the image, but the less light reaches the image plane, resulting in a longer exposure time.
  2. The distance between the pinhole and the image plane determines the size and focus of the image, following the principles of geometric optics.
  3. Pinhole cameras produce an inverted, real image due to the way light rays travel through the small aperture and project onto the image plane.
  4. The image quality of a pinhole camera is limited by the size of the pinhole, which affects the sharpness and brightness of the image.
  5. Pinhole cameras have a very large depth of field, meaning that objects at different distances from the camera will all be in focus.

Review Questions

  • Explain how the size of the pinhole in a pinhole camera affects the image quality and exposure time.
    • The size of the pinhole in a pinhole camera is a critical factor in determining the image quality and exposure time. A smaller pinhole will produce a sharper image, as it allows light rays to pass through the aperture with less diffraction, resulting in a more focused projection on the image plane. However, a smaller pinhole also allows less light to reach the image plane, which means the exposure time required to capture a well-exposed image will be longer. Conversely, a larger pinhole will allow more light to reach the image plane, reducing the exposure time, but the image quality will be compromised due to increased diffraction and a less focused projection.
  • Describe how the distance between the pinhole and the image plane affects the size and focus of the image in a pinhole camera.
    • The distance between the pinhole and the image plane in a pinhole camera is a key factor in determining the size and focus of the projected image. According to the principles of geometric optics, the farther the image plane is from the pinhole, the larger the projected image will be, but the less focused it will appear. Conversely, the closer the image plane is to the pinhole, the smaller the image will be, but the more focused it will appear. This relationship is governed by the focal length of the pinhole camera, which is the distance between the pinhole and the image plane. By adjusting this distance, photographers can control the size and focus of the image captured by the pinhole camera.
  • Analyze how the inverted, real image produced by a pinhole camera relates to the ray aspect of light and the principles of geometric optics.
    • The inverted, real image produced by a pinhole camera is a direct result of the ray aspect of light and the principles of geometric optics. As light rays pass through the small pinhole aperture, they travel in straight lines and project an inverted image onto the image plane, following the laws of geometric optics. This is because the light rays from the top of the scene cross at the pinhole and then diverge to the bottom of the image plane, while the light rays from the bottom of the scene cross at the pinhole and then diverge to the top of the image plane, creating the inverted image. This inversion is a fundamental characteristic of pinhole cameras and is a direct consequence of the way light rays behave when passing through a small aperture, as described by the ray aspect of light.