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Physics 1230: Light and Color Ivan I. Smalyukh, Instructor

Office: Gamow Tower, F-521 Email: ivan.smalyukh@colorado.edu Phone: 303-492-7277 Lectures: Tuesdays & Thursdays, 3:30 PM - 4:45 PM Office hours: Mondays & Fridays, 3:30 PM – 4:30 PM TA: Jhih-An Yang jhihan.yang@colorado.edu.

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Physics 1230: Light and Color Ivan I. Smalyukh, Instructor

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  1. Office: Gamow Tower, F-521 • Email: • ivan.smalyukh@colorado.edu • Phone: 303-492-7277 • Lectures: • Tuesdays & Thursdays, • 3:30 PM - 4:45 PM • Office hours: • Mondays & Fridays, • 3:30 PM – 4:30 PM • TA: Jhih-An Yang • jhihan.yang@colorado.edu Physics 1230: LightandColorIvan I. Smalyukh, Instructor Class # 14 Chapter #4: Cameras & Photography

  2. Equivalent exposure settings (same light) ¼ sec. lets subjects move Background in focus(good depth of field) 1/250 sec. stops motion Background out of focus

  3. Which f-number gives half the light of f-4? • f-2 • f-2.8 • f-4 • f-5.6 • f-8 f = F/D, so you need a LARGER f-number for less light. 5.6 is sqrt(2) smaller than 4, so twice the light.

  4. Which pair gives the same amount of light? 1/30 sec. and f number 4 and • 1/120 sec. and f-1 • 1/120 sec. and f-2 • 1/120 sec. and f-4 4x more light for ¼ the time.

  5. Lec. 9: Ch. 4 –The Camera and Photography\ Camera parts Lenses for cameras Controlling light Photography as art Photography as science We are here 5 5

  6. Albert Bierstadt Looking Down Yosemite ValleyOil painting 1865 6

  7. 7 Ansel Adams

  8. Albert Bierstadt Looking Down Yosemite ValleyOil painting 1865 William Henry Jackson. Mountain of the Holy Cross. 1873. Photography replaced painting to describe the western US 8

  9. Wright Bros., 1903 Jackalope, 2003? Photography as proof. 9

  10. Alfred Stieglitz 1864-1946 Photography as art 10

  11. Edward Steichen, 1879-1973 Glamour photography 11

  12. Edward Weston 1886-1958 Compare to 15th century painting with folded cloth

  13. Imogen Cunningham 1883-1976 Ansel Adams by Cunningham

  14. “Fine focus” Means directional lighting “Soft focus” (not out of focus) Means diffuse lighting

  15. 15 Ansel Adams Snake River 1942

  16. Lec. 12: Ch. 4 –The Camera and Photography Camera parts Lenses for cameras Controlling light Capturing images Digital images We are here How do we capture and save the image? 16 16

  17. Cameras existed for hundreds of years (pinhole and lens versions) The revolution (early 19th century) was FILM: The method to store and reproduce the images. Nowadays, we rarely use films

  18. 18 Ansel Adams

  19. Electronic device for storing images CCD: “Charge Coupled Device”. Digital Image Storage: The CCD Wires go to computer memory. Light sensor area

  20. Electronic device for storing images CCD: “Charge Coupled Device”. Digital Image Storage: The CCD Notice the colors. RGB colored filters in front of the sensors. The Bayer filter. Light sensor area

  21. Electronic device for storing images CCD: “Charge Coupled Device”. Digital Image Storage: The CCD Typical array is several thousand by several thousand. 1000x1000 = 1,000,000 Pixels, OR 1 MegaPixel. Rectangular array of PIXELs

  22. For photography of objects at different distances from us we use • A. Camera with CCD that has at least 5 megapixels; • B. Small aperture (large f-number); • C. Large aperture (small f-number); • D. Short exposure; • E. A, B, C, & D

  23. For photography of moving objects we use • A. Camera with CCD that has at least 5 megapixels; • B. Small aperture (large f-number); • C. Large aperture (small f-number); • D. Short exposure and larger aperture; • E. A, B, C, & D

  24. Extra credit questions • What settings we use for small depth of field? • What settings we use to make photos late in the evening (not much light)? • What would you do to make a photo during a very sunny day? • Explain how the photo on the left was done

  25. Review: To help you in your preparation for the exam (since many of you find the problems on lenses and curved mirrors somewhat difficult, we briefly review only this part) Exam time: Regular class time on Tuesday, Oct 11

  26. http://micro.magnet.fsu.edu/primer/java/mirrors/convex.html

  27. Ray Tracing: One method to understand spherical mirrors and lenses. Example: • Or (B): • The image is LEFT or RIGHT of the lens. • The image is REAL or VIRTUAL. This device is the ‘magnifying glass’. The image appears larger than the object.

  28. Ray Tracing: One method to understand spherical mirrors and lenses. Example: SI SI is the image height SO is the object height SO What is the magnification? Ray tracing plus a ruler to measure things and you can determine magnification.

  29. Object distance, image distance, focal length Xo Xi F

  30. Magnification formula S0 = object height Si = image height Note the similar triangles. We do the following: Image on opposite side of lens? XI is positive (otherwise negative) Image on opposite side of axis? SI is negative. (otherwise positive) Object lengths are ALWAYS POSITIVE. Demo: big mama lens and bulb

  31. The lens equation:The land of “One-Over-Everything!” F = focal length XO = object distance XI = image distance Usually, F and XO are given. We want to find XI Distant objects: Let Xo be very large, say 1,000,000 meters. Then 1/Xo = 0.000001, which is very small. You can ignore it. Then For distant objects, the image is at the focal point (ask a burnt ant) Demo: find focal length of lenses

  32. Exam time: Regular class time on Tuesday, Oct 11 Good luck on the exam! P.S. At home, go through the Photography guide on the next two slides

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