1Camera parts1. Lens, focal length2. Shutter (on the lens)3. Diaphragm (on the lens)4. Focusing screen or LCD5. Film (or CCD chip)We are hereLec. 13: Ch. 4 –The Camera and PhotographyTuesday, October 5, 2010We covered these 26 slides. Exam 1 HistogramMedian score = 50. A >65 about B > 50, Failing <38 about. 0510152025303540450102030405060708090100MoreFrequencyFACB3Film – how it works• 1. Plastic film is coated with emulsion containing a silver compound (silver bromide). The coated side faces the lens. • 2. Light breaks chemical bonds with silver. This is the latent image.• 3. Chemical developer releases silver into black grains. This is the negative image. • 4. A lens system projects the negative image onto a piece of coated paper, which is developed into a positive image. 35 mm film comes in a light-tight cartridge4Positive and negative. The film(negative)The print5Latent imageDeveloped imageμ = micrometer6Film speed and ASA number• “Faster” film (ASA400) needs less light. • Trade-off: Faster film is “grainier,” (bigger grains) • meaning less detail in the image. • Film speed has a number: – ASA 25 is slow with fine grain. Use outside in sun. For example, in sunlight, f/8 and 1/25 sec. will be ok. – ASA 100 is medium speed, good for inside shots. In sunlight, f/8 and 1/100 sec. – ASA 400 is good for low lighting. In sunlight, f/8 and 1/400 sec.7Photography (cont’d)• Polarizing and haze filters• Tripod• 35 mm slides8Polarizer selects one polarization(rejects the other)Polarization is perpendicular to the plane containing the incident and scattered rays (vertical for low sun)Polarization parallel to the water surface(horizontal) Walden pondSunlight is randomly polarized9UV/Haze filter• Scattered sunlight from tiny particles (including atoms) contains more blue and UV.• Hint: That is why the sky is blue, ocean is blue. • Haze is sunlight scattered from tiny particles.• UV filter does not pass the scattered UV so the scene is less hazy. Haze Haze Haze HazeYellow fog lights on cars don’t contain blue that would scatter from the fog. 10TripodHolds the camera steady for long exposures• Astronomy, indoors (museums, weddings)• Low light, any exposure 1/5 sec or longer• Telephoto lenses, 1/100 sec or longer1135 mm film photographyWe look at 35 mm color slides that showWide angle and telephoto lensDepth of fieldShutter speed Harsh and soft lightingRainbows, fog, crepuscular rays, etc. PerspectiveMoon, cometCavesDemo: slide show, next slide is black for projection of slides1313Lec. 13: Ch. 4 –The Camera and PhotographyPhotography as artCamera partsPhotography as scienceWe are hereScientific photography and imaging• Photomicrography• Stop action• Time lapse video photography• Astrophotography– ground based – space based• Not-light photography 14PhotomicrographyInsect leghttp://www.nikonsmallworld.com/15Harold Edgerton – flash photography 1940s & 50sA fast flash of light, 1/10,000 sec. for example, stops motionMilk drop onto red surface Water faucet16More Edgerton photosDuration of flash of light is probably a few microseconds. 17Time lapseTake photos at 1 sec intervals (for example)Show at 30 frames per second (for example) • Milky Way risingShot at 1 minute per frame, shown at 30 frames per sec. , 1800 times normal speedhttp://wlcastleman.com/astro/tsp09/tsp_mwcore_rise_720x480.mp4• Mentos and Diet Coke (1200 fps)1/40 of normal speedhttp://www.youtube.com/watch?v=NlicfTzFEPo• San Francisco time lapse http://vimeo.com/1506955118Astrophotography – Hubble TelescopeThe large mirror intercepts lots of light and concentrates it onto the film or CCD detector.Long exposures, hours, are used. 19Hubble astrophotographs20Not-light photography• X-rays shadowgraphy• Computer aided tomography (CAT)• Ultrasound, sonar• Radio astronomy • Magnetic resonance imaging (MRI)21Radio astronomy maps radio brightnessGalaxy M87 squirts a jet of material.The detail shows the origin of the jet.Probably, the source is powered by a black hole. Images are computer-constructed using many antennas. 22Ultrasonographyf = 2 – 18 MHz implies wavelength of about 0.1 mm23X-ray shadowgraph (2-d)There is no focusing lens. The x-rays go from a point-like source to the film. What is recorded is a negative of a shadow. 24X-ray tomography (3-d)A computer produces a 3-d image from many x-ray shadows from different directions.Shown above is someone’s head. 25Magnetic resonance imaging (MRI)The science: a magnetic field and radio waves detect spinning nuclei in atoms. The location of the signals can be pinpointed and made into an image by computers. Advantage: better discrimination between types of tissue. Disadvantage: