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5 Image Capture Media. 5 Image Capture Media Describe the differences between digital image capture and the traditional chemical method of image capture.

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Presentation on theme: "5 Image Capture Media. 5 Image Capture Media Describe the differences between digital image capture and the traditional chemical method of image capture."— Presentation transcript:

1

2 5 Image Capture Media

3 Describe the differences between digital image capture and the traditional chemical method of image capture. Explain the operation of a sensor in capturing an image. Distinguish between the physical structures of black-and-white film and color film. Explain the method by which a latent image is formed.

4 Describe the film speed rating system as a measure of sensitivity to light.
List the various types and forms of film. List the advantages and disadvantages of color negative and color positive films. Demonstrate the film loading procedures for common types of cameras.

5 Digital vs. Film Image Capture
Electronic arrays capture images on photo sites Digital sensor captures image Camera processes image File stored on removable device Film records a latent image Made permanent by chemical processing

6 Digital vs. Film Image Capture (Cont.)
Photography long considered an image-capture process requiring chemicals and light Digital photography far more popular than film Pixels arranged to form area array Digital images stores as files

7 Film Capture and Processing

8 Digital Imaging Process
Light strikes pixel Generates electrical charge Charge strength varies with brightness Electrical charge converted to analog signal Analog signal converted to digital signal processed by camera’s firmware CCD and CMOS devices process signals differently

9 Digital Imaging Process (Cont.)

10 Digital Cameras See Only Gray
Bit depth determines gray levels 1-bit pixel = 2 shades (black or white) 8-bit pixel = 256 shades Color information records filtered light to obtain grayscale channels

11 Bayer Pattern Filter decals on pixels Twice as many green filters

12 Sensor Sizes Full-frame print (24 mm  36 mm) APS-size (17 mm  30 mm)
Same as 35 mm film Most professional cameras APS-size (17 mm  30 mm) Compact and prosumer cameras

13 Pixel Sizes Full-frame pixels 1/3 larger than APS
More light-sensitive Existing pixel values averaged to create new pixels through interpolation

14 Scanning Backs and Studio Cameras
Linear arrays used exclusively Trilinear arrays preferred to area arrays Long exposures generate heat which can cause digital noise and blooming

15 Digital Image Storage Memory card flexible removable memory device

16 Digital File Formats Files may be compressed to use less storage space
RAW TIFF (.tif) JPEG (.jpg)

17 Removable Storage Devices
Secure Digital (SD) CompactFlash (CF) Capacities from 128 Mb–64 gigabytes (GB) Memory Stick xD-Picture Microdrive SmartMedia Lexar/SanDisk/Fujifilm/Sony Corporation/Hitachi

18 Storage Capacities Depends on sensor size and file type

19 Card Speed Transfer rate from camera to card
Useful for sports and action photography Cameras also possess a buffer, or internal memory

20 Film Image Capture Evolution of film Daguerrotype/tintype
Wet (collodion) glass plates Dry (silver bromide) glass plates Roll film

21 Physical Structure of Film
Flexible base material Light-sensitive (emulsion) layer(s) Special-purpose layers

22 Black-and-White Film Film base Single emulsion layer
Three additional layers: Supercoat Subbing layer Antihalation layer Surfactant used as wetting agent

23 Color Film Film base Three emulsion layers Five additional layers

24 How Light Affects Film Photons affect silver halides
Silver bromide ions Silver bromide crystals contain sensitivity specks Silver clumps form latent image Negative density proportional to light Positive (print) will reverse values

25 Characteristic Curve Relates exposure to density
Different for each film First section = film base plus fog Middle-density section = straight-line section Right end = shoulder

26 Characteristic Curve (Cont.)

27 Film Speed Ratings Measurement of light-sensitivity
Lower number = less sensitive Higher number = more sensitive Sensitivity doubles/halves with each ISO step Film grain increases with speed Based on requirements by International Standards Organization (ISO)

28 Film Speed/Grain Relationship
Grain increases along with film speed Film emulsion improvements reduce grains at high speeds Tabular grains Chromogenic film produces a grainless black-and-white image

29 Reversal Film Transparency is “first generation” image
Exposure more critical than print film Two-step development process Negative silver image Color dyes (positive) replace silver

30 Negative/Positive Film
Most common film type Monochrome and color Wide range of speeds Processing readily available Developed film is negative Print is positive (“second generation”) image High-contrast lithographic film

31 Instant-Print Film Film + developer Mostly replaced by digital imaging
Print in 60 seconds or less Monochrome and color Mostly replaced by digital imaging

32 Forms of Film Cartridge film Film in cassettes Almost obsolete
35 mm and APS Drop-in loading Lighttight cassette protects film Film loader required

33 Forms of Film (Cont.) Roll film Sheet film Medium-format cameras
Paper backing holds/protects film Sheet film Individual, thicker film sheets Must be used in holders 4″  5″ most common today

34 Where do the similarities between traditional and digital image capture end?
When the light rays reflected from the subject reach the camera’s image receiver.

35 Many digital camera sensors have red, blue, or green color filter decals applied over the individual pixels in an arrangement called a _____ pattern. A. Bartel B. Bayer C. Boxcar D. Bizet

36 Color film may have as many as nine layers, including _____ separate emulsion layers. three

37 True or False? Photons of light striking the film emulsion form a latent image. True

38 Film with an ISO rating of 400 is ____ times more sensitive to light than an ISO 100 film. four

39 Antihalation layer APS-size
The bottommost layer of film, located on the back side of the base. This layer prevents light rays from being reflected back through the base and emulsion. Without this layer, reflected light could form halos (halation) around bright objects in the photograph. APS-size Sensor used in most digital cameras. The sensor is approximately 17 mm  30 mm in size, like the film used in Advanced Photo System cameras. (Full-frame sensors are 24 mm  36 mm, corresponding to the 35 mm film frame.)

40 Area array Bit depth Blooming
A grid made up of rows and columns of electronic sensors. Bit depth A numeric expression of the number of shades of gray a pixel is capable of displaying. Blooming In a digital photo, the smearing or bleeding of some color pixels, especially red, into adjacent parts of the image.

41 Buffer Card speed Characteristic curve
Internal memory in the camera that functions as a holding tank for image information already processed but not yet transferred to the memory card. Card speed A measure of how rapidly image files can be transferred from the camera to the memory card. Characteristic curve An S-shaped graph that serves as a “snapshot” of a given film’s reaction to light. It shows the relationship between exposure and density increase.

42 Chromogenic film Collodion
A type of black-and-white film that produces an essentially grainless image composed of dyes, rather than silver. Collodion A basic emulsion ingredient of the wet-plate process, consisting of cellulose nitrate dissolved in ether or alcohol. A halogen salt such as potassium iodide also is dissolved in the mixture.

43 Color information CompactFlash (CF)
Red, green, and blue values recorded by filtering the light striking the digital sensor to obtain three different grayscale channels. CompactFlash (CF) A small, solid-state memory card, available in a wide range of capacities, that is slipped into a slot on the camera.

44 Compressed file Digital noise
One that has been converted to a format that allows it to be saved in a smaller size to take up less storage space or to speed up transfer time. Digital noise Tiny light-colored spots especially noticeable in shadow areas of a scan or image capture.

45 Digital signal Drop-in loading
Image information that is encoded as a series of on/off states (usually represented by 1 or 0), rather than varying continuously (an analog signal). Drop-in loading A feature of Advanced Photo System cameras that allows the consumer to merely open a film door on the camera and insert the cassette. The film is then automatically loaded and advanced to the first frame.

46 Electronic array File File formats
An arrangement of millions of tiny solid-state photo sites used to capture an image in a digital camera. File An individual digital image that can be stored, transferred, or manipulated. File formats Different modes of saving image data, such as JPEG or TIFF.

47 Film A light-sensitive, silver-based emulsion coated on a smooth, usually flexible plastic, base. Film base plus fog The minimal density of a clear film area, such as the strip between frames. The tiny amount of density is caused by the processing chemicals (rather than light). Also, a short, horizontal section at the left end of the characteristic curve.

48 Film loader A lighttight device that holds a roll of bulk film and allows a desired number of frames of film to be wound into a cassette. Film speed The film’s sensitivity to light—the higher the film speed, the less light is needed to create a latent image on the emulsion.

49 Filter decals Firmware
Transparent color overlays applied in a checkerboard pattern over individual sensors in a CCD or CMOS array. There are usually twice as many green filters as red or blue filters, because human vision is most sensitive to the light values contained in the green channel of a color image. Firmware The built-in program found in a digital camera or similar device.

50 Full-frame print Gigabytes (GB) Gray levels
A print made without cropping. A full-frame print from a 35 mm negative on an 8″  10″ sheet would result in an image approximately 6 ½″  9 ½″. Gigabytes (GB) A quantity used to describe storage capacity of digital devices, such as computer memory or camera memory cards; approximately equal to 1 million bytes. Gray levels The distinct “steps” between pure white and pure black.

51 Image-capture process
Using a camera to record a scene on film or a digital sensor. International Standards Organization (ISO) A body that publishes standard sets of requirements to ensure uniformity of such items as film speeds. Interpolation In scanning or image-editing applications, the creation of new image pixels by averaging the values of the surrounding existing pixels.

52 Ions Atoms carrying a positive or negative electrical charge. JPEG The most common compressed file format, developed by the Joint Photographic Experts Group. It can be used to reduce file size by a small or large amount. Latent image A photographic image that will not become visible until developing chemicals are used to bring it out and make it permanent.

53 Linear array Lithographic film Memory card
Image-capture arrangement consisting of a long array containing only one to three rows of CCDs. Linear arrays are used in scanning-back cameras for studio work, and in flatbed scanners. Lithographic film A high-contrast material that produces an image without graduated tones. The film is either black or clear. Sometimes referred to as “lith film”. Memory card A digital storage device used in cameras; available in a number of forms and a wide range of capacities.

54 Memory Stick Microdrive RAW
A form of memory card used primarily in Sony cameras. Microdrive A tiny hard drive the size of a CompactFlash memory card. RAW File containing the basic image information captured by the camera’s sensor and saved with a minimal processing.

55 Scanning backs Secure Digital (SD) Sensitivity specks
Studio capture devices that make use of a trilinear array, rather than an area array. Secure Digital (SD) Memory cards that are physically smaller and thinner than CompactFlash cards, and are available with capacities from 128Mb to 8Gb. Sensitivity specks Impurities believed to play the important role of focal points or sites for the formation of the silver clumps making up the latent (undeveloped) photographic image.

56 Shoulder Silver halide salt SmartMedia
The right end, or high-density portion, of the characteristic curve, representing the highlights of a scene. Silver halide salt A light-sensitive chemical compound used as a key ingredient of photographic emulsions. SmartMedia An early form of removable memory card for digital cameras.

57 Straight-line section
The middle-density portion of the characteristic curve, where the density/exposure relationship is most nearly proportional. Subbing layer A very thin coating of pure gelatin that helps bond the emulsion to the base.

58 Supercoat Surfactant Tabular grains
The very thin, tough topmost layer of the film. Its primary purpose is to protect the emulsion from abrasion during exposure and processing. Surfactant An ingredient of the film’s supercoat that promotes absorption of processing chemicals to help ensure even development. Tabular grains A thinner flatter form of silver halide grains, developed to allow an increase in film speed without a corresponding increase in visible grain.

59 TIFF Trilinear array xD-Picture Tagged Image File Format.
In a scanner or scanning back, a bar containing three rows of sensors that is moved across the image capture area. One row of sensors is filtered to capture red wavelengths; one is filtered for green, and the third is filtered for blue. xD-Picture Tiny memory cards, about the size of a postage stamp, used in some digital cameras. They are available in capacities of 16Mb to 2Gb.


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