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The Optics of Cameras

Learn about the fundamental elements of photography, including F-stop, focal length, and ISO, and how they impact your photos. Explore how different camera settings affect light and focus, and practice using them to capture amazing shots. Discover the art and science of camera optics to enhance your photography skills.

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The Optics of Cameras

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  1. The Optics of Cameras Joe Two Bear Jason Waskiewicz

  2. Elements of Photography • F-stop: size of aperture (hole) the light comes through • Focal Length: distance at which light is focused • ISO: ability of the camera to collect light (not part of lab) • Speed: how quickly a picture is taken (slower lets in more light)

  3. General Camera Parts Mirror Eyepiece Opening Shutter Lens(es)

  4. Activity 1 – F-stop • F-stop controls how big the opening is that lets in light • F-stop numbers are backward: small numbers mean a big opening, big numbers mean a small opening

  5. How an Opening Works • Early camera: pinhole camera • Light reflects off an object in all directions • Pinhole selects only a tiny amount of the reflection • Result is a sharp image These light rays never enter the pinhole.

  6. Try it out! Viewer • Work through Activity 1 • Demonstration of Scattering • Pinhole Viewer (shown here) Parchment Paper Pinhole

  7. Sample Results I was able to see even the base of the bulb! This was a very difficult photograph to take; it actually looks better through the box.

  8. F-Stop Post-Discussion Adjustable Opening

  9. Effects of Opening Size Small Opening Large Opening

  10. Small F-stop (Large Opening) Boy stands out because he is in focus • Large opening (small f-stop) creates blurry background • Light comes in at all angles • Only small part of image comes in with correct focus • Great for portraits • Also useful for low-light photography People in the background are out of focus

  11. Low-light Photography • This is not in the student version, but this is an example of a picture taken in extremely low light, but it looks good because I had the lens wide-open!

  12. Large F-stop (Small Opening) • Small opening (large F-stop) makes the image sharper throughout • Fewer light rays come in to distort focus • More of the image is sharp • Great for landscapes • Not useful in low-light photography (without a tripod) Buttes in the distance are sharp Abandoned farmhouse is also sharp

  13. Activity 2 – Focal Length • Many cameras have zoom lenses (like the far right) which have adjustable focal length • Focal length measures the distance at which the image of an object comes into focus • Different lenses have different focal lengths and uses

  14. Comparing Focal Lengths 18mm lens good for wide angle (like a building – abandoned farmhouse earlier) 50mm lens like the human eye views the object

  15. Comparing Continued 85mm has slight magnification, good for portraits (picture of the boy earlier) 55-250mm zoom lens at 250mm zoom

  16. Start Activity 2 • First do the Estimation • Then do the Measuring the Focal Length • Illustrated to the right • Note how the image projects on the screen • Also note that the LENS moves, there is some distortion in this picture

  17. First Activity • The only difficulty I had with this one was that you need to project the image straight on. Don’t try to project an image that is at an angle.

  18. The Two Sample Graphs – Actual Results from Bowman!

  19. Focal Length Discussion • Focal length is the distance from the lens at which parallel light rays entering the lens focus on a single point • When you project the sun with a magnifying glass, you are applying the focal length!

  20. Real LensesCount them: 9 actual lenses in the lens Lens(es)

  21. Activity 3 – The Telescope • Actual camera lenses consist of several lenses put together • All 3 lenses here are “telephoto” lenses • None of these are the actual length of the focal length because of how several lenses interact.

  22. The Telescope • Activity 3 puts 2 lenses together as a telescope • Illustration shows (roughly) the setup for a telescope.

  23. View Students Will See Through the Telescope Without Telescope With Telescope: and what a tough photograph to take!

  24. Final Discussion • Even most of the less expensive cameras allow adjustment of speed, ISO, f-stop, and focal length • With a little knowledge, you can take much better pictures • Experiment, try out the features of your camera: digital makes it cheap • Photography is fun, and most of us own at least a basic camera

  25. UND is awesome

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