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Digital Photography

Digital Photography. Photo Organization September 13. Checkpoint. Signed Camera Check Out Form Brainstorm notes Think about what types of images you may take Think about when you may take them Think about how you may edit them in class

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Digital Photography

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  1. Digital Photography Photo Organization September 13

  2. Checkpoint • Signed Camera Check Out Form • Brainstorm notes • Think about what types of images you may take • Think about when you may take them • Think about how you may edit them in class • Keep in mind that you may take several thousand photos this semester, and may have several saved versions of each

  3. Organization • Let’s discuss what we came up with • We can always use somebody else’s ideas for this, if we like it better than the way we did it! • You guys have it much easier for organization than past classes, because Adobe CS2 offers a lot of cool stuff • Note: only the black computers have CS2, not the silver ones

  4. Adobe Bridge

  5. Adobe Bridge • Views: • Thumbnail • Filmstrip • Details • (Versions and alternates) • For all these views, you can change size of image displayed

  6. Metadata File PropertiesIPTC Core - Standard bunch of metadata for filesCamera Data

  7. Keywords • Some pre-defined keywords, but the user has complete freedom in choosing Keyword Sets and individual keywords

  8. Ranking • Built-in easy way to rank images • Select an image and the dots beneath the image are selectable and change to stars, based on your choices

  9. Other Features • Rotation of images • Labeling • Filtering (based on rank or labels) • Find - can base it on several criteria • And more!

  10. Lab Time • You can begin to use Bridge • To set up your organization structure • To rotate any images • To identify and delete any “out-takes” • To assign rankings, keywords, etc • Have fun, but begin a solid structure that you can build upon

  11. Homework • Read Chapter 2 • We will discuss tomorrow & Thursday in class • It is difficult material!

  12. Light and Sensors Lecture 04 September 14, 2005

  13. Entering complex material… MDP Chapter 2

  14. Photography is about light • Photography = “to write with light” • So we have to understand a little about light to understand how cameras work

  15. How we see light • White Light (from the sun) is made up of colors, and each light has a certain wavelength • Light waves are either reflected, absorbed, or transmitted – which is determined by the object that the wave hits • The color we see is based on the type of light sent to our eyes  An apple is red because it reflects red light • For an objects to be black, all wavelengths of light are absorbed, no light is reflected • The primary colors of light are red, blue and green (we will talk more about this later) http://imagers.gsfc.nasa.gov/ems/visible.html

  16. How a camera takes a picture • A camera is like our eyes – to “see” color, it must be able to capture the light that is reflected from objects • Reflected light enters the camera – passing through the lens’s glass (which may have many elements) • This light gets focused onto a sensor • The sensor is sensitive to light, so it captures the light and stores it – creating the image

  17. What happens inside the camera

  18. After light hits sensor • Allows viewing of image on viewfinder or LCD • Viewfinder • can roughly match what sensor sees • Could be like a mini tv • Might be a reflection of the light from the lens • Push the shutter release button – the shutter opens/closes for a period of time • Camera may autofocus, lock exposure, cause flash to fire, etc • Digital information is stored on memory – the speed that it takes to write the information to memory depends on size of image, type of compression & compression ratio, and speed of media)

  19. Sensors and colors • Sensors can’t see colors – they can only collect the brightness of the scene • Colored filters are used to limit range of light for each pixel • So each pixel reads a value for the red, green, or blue to define the final color – sometimes only one color is read, and the others need to be interpolated • Different sensor types have different ways that they deal with this limitation

  20. How a sensor works • The sensor is sensitive to light, so it captures the light and stores it – creating the image – how does this work? • Sensor is made of millions of individual light sensitive pixels (diodes) • This sensors are arranged in a grid, or array • Each pixel collects a charge proportionate to the intensity and amount of light • Pixels translate light into specific voltage values • The strength of the charge corresponds to the brightness of the pixel (up to a certain point) • A pixel can only hold so much charge, if too much builds up, it could overflow to neighboring pixels – a process called blooming – proper exposure will eliminate most blooming, if in doubt, underexpose the image • Some sensors have mechanisms built in to minimize effects of blooming

  21. What happens with the charge? • Light has been collected as voltage (charge) • Voltage information has an infinite amount of variation, smooth transitions • This is called ANALOG information • The camera needs the information to be in discrete digital numbers to store the picture • So the sensor (or other circuitry) has to perform analog to digital conversion

  22. Digital Data • The digital data can be written to the cameras memory, and represents the light information that hit the sensor, but in a way a computer can understand. • The image sensor determines the resolution and quality of the final image (by the number of light-sensitive pixels that collect information)

  23. Types of Sensors • Sensors work by having light-sensitive pixels that collect the light • This sensor technology is relatively new (within the last 30 years) and is still being improved. • Physicists are working with different materials and making different kinds of sensors that capture the light

  24. CCD Image Sensor • CCD = Charge Coupled Device • Grabs part of picture with each exposure • Array arranged in mosaic or Bayer pattern • Each pixel registers one of 3 colors • 50% green pixels are registered, 25% (each) blue and red registered • Other colors must be interpolated (guessed) • True resolution of camera is reduced because not all the light is being recorded • Array of pixels gather light and translate to a voltage • CCD sensor is just an analog device – it does not process voltage; so additional circuitry in the camera must do that • Each row read one at a time (like a conveyer belt)

  25. Foveon CMOS Image Sensor • CMOS = Complementary Metal Oxide Semiconductor • Captures RGB light at each pixel; no interpolation (3 layers of photodetectors) • Uses properties of silicon to register light absorption at different layers • No interpolation is necessary – less light is wasted • But sensor is less sensitive, so information is still lost • Pixels in sensor include the circuitry to convert voltage to the digital data • done in parallel – each pixel can be processed individually and immediately • Can record an image more quickly (theoretically) • Use less power because several functions are included on the image sensor

  26. Which image sensor is better? • Currently, CCD has better image quality and a better range • But like we said, it doesn’t do digital conversion, so it uses more power • It requires special production techniques – but generally has less noise • But, CMOS is catching up & is being used in professional level cameras because the sensors consume less power • CMOS sensors are less expensive to produce

  27. Tomorrow • Tomorrow we will look at how lenses affect what light reaches the sensor – and how that affects what image the camera sees.

  28. Lenses and Exposure Lecture 05 September 15, 2005

  29. The Lens • Lens is the eye of the camera • It captures and focuses the light onto the sensor • The lens affects the quality of the image & the kinds of pictures that you can take • What matters: • Quality of lens • Amount of light it can transmit • Focusing range • Amount of magnification

  30. Lenses: Focal Length • Focal Length: The distance from the rear nodal point of the lens to the point where the light rays passing through the lens are focused onto the image sensor • Measured in millimeters (Film standard is 35mm) • Think of it as the amount of a lens’s magnification • The longer the length, the more the lens will magnify the scene Picture from Real World Digital Photography Book

  31. Focal Length Photos from Canon Website Canon Photo Shooting- Techniques (Using a telephoto lens)

  32. Lens Aperture • Size of the opening that admits light to the sensor, relative to the magnification or focal length of the lens • f-stops (denominators of fractions indicating relative size of opening) • Each stop you open up doubles the amount of light reaching the sensor • Maximum aperture – lets in more light – good for dim lighting • Minimum aperture – how much light can you block from the sensor (used for bright lighting) • Also can increase depth-of-field f8 f4 f2

  33. Lens Speed • Lens Speed • Amount of light the lens transmits at maximum aperture • A lens with maximum aperture of f2 is “fast” compared to a lens with max aperture of f8 which is “slow” • Fast lens = large aperture - allows lens to transmit more light • Slow lens = small aperture - little light gets through

  34. Kinds of Lenses • Zoom Lens • Allows you to enlarge or reduce an image without having to get closer or farther away • Optical Zoom - changes the effective focal length of the lens • Telephoto lens • Compresses the apparent distance between objects, making them appear to be closer together • Wide-angle lens • Expands apparent distance between objects, giving vast areas of foreground, making distant objects appear to be farther away

  35. Wide vs. Telephoto Lenses Photos from Canon Website Canon Photo Shooting- Techniques photo with a wide-angle lens (35 mm) a photo with a telephoto lens (equivalent to 150 mm)

  36. Wide-angle lens • Wide angle lenses let you shoot over a wide range (vertically) • But it makes things in the background appear even further away (large depth-of-field) • It can cause strong distortions in up-close photos of subjects Photos from Canon Website Canon Photo Shooting- Techniques

  37. Telephoto Lens • Lets far away objects appear closer • Makes background objects appear to be close to subjects • Can be used to artistically blur the background (short depth of field) Photos from Canon Website Canon Photo Shooting- Techniques

  38. Shutter Speed • Is measured in seconds or fractions of a second • The duration of time the shutter opens and closes during an exposure process • How long the light flows through the lens and onto the image sensor

  39. Introduction to Exposure • Exposure is the amount of light striking the sensor • Three factors determine correct exposure • Amount of light in scene that strikes the image sensor • Length of time the sensor is exposed to light • Sensitivity of the sensor • Think of each pixel on the sensor as a little bucket that catches photons of light as they pass through the lens. • Bucket must fill up to a threshold point before the pixel will register it as part of the image • Raising or lowering the threshold mark will decrease or increase the sensitivity of the sensor

  40. Exposure • Aperture (f-stop) determines how many photons are admitted at once (like a funnel) • Shutter speed determines how much time the photons have to strike the sensor (like a valve controlled by a timer) • Aperture & shutter speed work together to create proper exposure • Buckets can be filled quickly with short shutter speed and large lens opening • Buckets can be filled slowly with long shutter speed and small lens opening •  Same exposure (same amount of light reaching the buckets)  RECIPROCITY – equivalent exposure values

  41. Reciprocity • Equivalent Exposures EV14

  42. Schedule • HW1 -- (For Friday, but bring on Tuesday) • Write 1/2 - 1 page (single-spaced) OR make a PowerPoint presentation of a mini biography of a famous photographer (not Ansel Adams), plus download or bring in 2-3 pictures taken by that photographer to show the class on Tuesdat • Tomorrow no coordinate classes this period. • HW2 - • Friday during class we will take pictures as part of Homework 2 (see website) and experiment with the lenses • Over the weekend - continue taking pictures as part of HW 2

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