C H A P T E R 5 Image Capture Media Permission granted to reproduce for educational use only.©...

C H A P T E R

5Image Capture Media

Permission granted to reproduce for educational use only.

© Goodheart-Willcox Co., Inc.

O B J E C T I V E S

• 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.



O B J E C T I V E S

• 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.



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



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



Film Capture and Processing



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



Digital Imaging Process (Cont.)



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



Bayer Pattern

• Filter decals on pixels – Twice as many green filters



Sensor Sizes

• Full-frame print (24 mm 36 mm)– Same as 35 mm film– Most professional cameras

• APS-size (17 mm 30 mm)– Compact and prosumer cameras



Pixel Sizes

• Full-frame pixels 1/3 larger than APS– More light-sensitive

• Existing pixel values averaged to create new pixels through interpolation



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



Digital Image Storage

• Memory card flexible removable memory device



Digital File Formats

• Files may be compressed to use less storage space

• RAW• TIFF (.tif)• JPEG (.jpg)



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



Storage Capacities

• Depends on sensor size and file type



Card Speed

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

memory



Film Image Capture

• Evolution of film– Daguerrotype/tintype– Wet (collodion) glass plates– Dry (silver bromide) glass plates– Roll film



Physical Structure of Film

• Flexible base material• Light-sensitive (emulsion) layer(s)• Special-purpose layers



Black-and-White Film

• Film base• Single emulsion layer• Three additional layers:

– Supercoat– Subbing layer– Antihalation layer

• Surfactant used as wetting agent



Color Film

• Film base

• Three emulsion layers

• Five additional layers



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



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



Characteristic Curve (Cont.)



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)



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



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



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



Instant-Print Film

• Film + developer– Print in 60 seconds or less– Monochrome and color

• Mostly replaced by digital imaging



Forms of Film

• Cartridge film– Almost obsolete

• Film in cassettes– 35 mm and APS– Drop-in loading– Lighttight cassette

protects film– Film loader

required



Forms of Film (Cont.)

• Roll 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



R E V I E W

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.



R E V I E W

Many digital camera sensors have red, blue, or green color filter decals applied over the individual pixels in an arrangement called a _____ pattern.A. BartelB. BayerC. BoxcarD. BizetB. Bayer



R E V I E W

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



R E V I E W

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



R E V I E W

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

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C H A P T E R 5 Image Capture Media Permission granted to reproduce for educational use only.©...

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