Introduction to Digital Photography

Introduction to Digital Photography
Glossary, Definitions, and Digital Concepts Instructor: David King

Digital Photography: Glossary, Definitions, and Concepts
Digital Still Photography was developed from Video Electronic Capture The first Still Cameras Captured an NTSC Video “Frame” An NTSC Video frame is 1/30 of a second. (NTSC Video plays at 30 frames per second.) A ‘FRAME’ is made up of two interlaced ‘FIELDS’ to create the full image. Each field is 1/60 of a second. Each field contains every other line of pixels on a screen. There are about 500 lines per screen in normal NTSC Video Filtering can raise this to about It is approximately equivalent to a 640 x 480 pixel image at 72 pixels per inch (‘Hi Def’ is approximately double that resolution). Instructor: David King

Digital Still Photography was developed from Video Electronic Capture One of the first viable cameras was the Sony ‘Mavica’ ™ which used 1.44 megapixel/3.25 inch ‘floppy’ discs to store its video-based images. Instructor: David King

Capturing an Electronic Image The image is captured with an imaging ‘chip’ or ‘sensor’ that converts light energy into an electrons that can be measured based on intensity. There are two technologies in use to make photo imaging chips. CCD = “Charge-Coupled Device” CMOS = “Complimentary Metal Oxide Semiconductor” Instructor: David King

Capturing an Electronic Image Is one technology better than the other? CCD = “Charge-Coupled Device” Initially less costly to manufacture More uniform readings since data goes through fewer ‘readers’ Less heat therefore less inherent signal noise Requires additional processing chips in system and high power use CMOS = “Complimentary Metal Oxide Semiconductor” Each pixel had its own reader More circuits on chip making for less system complexity Less power consumption and greater battery life Higher speed Instructor: David King

Capturing an Electronic Image Defining an Image chip of either type… A CCD or CMOS imaging Chip has Four major characteristics. (This is the digital equivalent to film types and formats.) 1. PHYSICAL DIMENSION/SIZE: That is, how big is the chip? Size is usually measured in millimeters (mm) or expressed in a label. “Full Frame” = 36mm x 24mm (Size of 35mm film image) “APS”/”DX” = 23mm x17mm – 22mm x15mm “4/3” = 18mm x (Olympus Only) Point and Shoot chips can range from 8mm x 6mm and down… Digital Backs (MF) are from 36mm x 36mm to 48mm x 48mm and up Scanning Backs (LF) are from 125mm x 100mm and up. Instructor: David King

Capturing an Electronic Image Defining an Image chip of either type… A CCD or CMOS imaging Chip has Four major characteristics 2. ASPECT RATIO: That is, what SHAPE is the chip? “Full Frame” and “APS”/”DX” = 3:2 like a 35mm camera “4/3” and most P&S (and Video) = 4:3 which is more like an 8x10 print Square = many Digital Backs produce a square image Instructor: David King

Capturing an Electronic Image Defining an Image chip of either type… A CCD or CMOS imaging Chip has Four major characteristics 3. PIXEL DIMENSION: That is, how many photo sites are on the chip? Dimension is measured in “Megapixels” (Millions of pixels) “DSLRs” = Currently: 6 Mp to 16.7 Mp “MF Backs” = Currently: 11 Mp to about 40 Mp “LF Backs” = 80 to over 120 Mp Point & Shoot = Currently 3 to 10 Mp Instructor: David King

Capturing an Electronic Image Defining an Image chip of either type… A CCD or CMOS imaging Chip has Four major characteristics 4. PIXEL SIZE/DENSITY: That is, how big is each photo site and how close are they to one another? Instructor: David King

Capturing an Electronic Image Other Major Camera/Back differences to consider… FRAME RATE for CONTINUOUS SHOOTING: That is, how fast can you take one shot right after another? IMAGE BUFFER: That is, how many images can be stored in the system buffer before it has to pause to empty onto the memory card? BUILD DURABILTY: Composite, plastic, metal and how is it sealed against weather and the elements? ERONOMICS: How easy is it to hold and shoot? How quickly can you get it into action or find all of the controls and buttons? LENS AVAILABILITY: What lenses and of what quality are available? In the end, picture quality is all about the GLASS! Instructor: David King

Capturing an Electronic Image Why is the lens so important? We need to see how a chip differs from film in how it records an image Instructor: David King

Capturing an Electronic Image Why is the lens so important? Instructor: David King

Capturing an Electronic Image Different cameras have different approaches to these issues. So Which is best? Or… What are the trade offs? IT ALL DEPENDS ON WHAT YOU ARE SHOOTING… JUST LIKE WITH FILM!!! We’ll address these issues in detail as the class goes on… Instructor: David King

Resolution versus Resolution A Few different kinds of resolution… In Film we had… Grain: A result of film speed and format size (Grain enlarged as the print was enlarged) In Digital we have… PPI = Pixels Per Inch (File resolution) (Does not change with enlargement…) DPI = Dots Per Inch (Printer ink resolution) LPI = Lines Per Inch (Offset reproduction resolution) LPMM = Line Pairs Per Millimeter (Lens resolution) Instructor: David King

Resolution versus Resolution Pixel density and a file’s pixels per Inch would seem to determine how fine can be the detail recorded in a file, But it is just the start… then there is “interpolation” Interpolation is calculating what goes between other known data. Extrapolation is calculating what lies outside the known data. Because a photo site only registers luminosity (the intensity of the light striking it) interpolation is the process by which the digital camera’s Processor determines color. But it has a major effect on resolution. Instructor: David King

Resolution versus Resolution – The “BAYER” Filter / Pattern Different processors interpolate differently but for this hypothetical 12x8 (96 pixel) chip, here is one way… Instructor: David King

Resolution versus Resolution – The “BAYER” Filter / Pattern Grid is divided into 4-block primary squares. Instructor: David King

Resolution versus Resolution – The “BAYER” Filter / Pattern The luminosity under each filter is measured and assigned. Then the next block is processed until all are completed. Instructor: David King

Resolution versus Resolution – The “BAYER” Filter / Pattern A primary pixel is assigned the resulting RGB value. Then the next primary pixel. Intermediate pixels discard the initial reading. Instructor: David King

Resolution versus Resolution – The “BAYER” Filter / Pattern Based on the primary pixels, the in-between pixels are interpolated. Instructor: David King

Resolution versus Resolution – The “BAYER” Filter / Pattern The averaged primary and interpolated in-between values are then sent to the memory card. Instructor: David King

Resolution versus Resolution – Other approaches… FUJI… Fuji arranges their photo sites in a diamond pattern to increase horizontal resolution then puts two sensors at each site; a large and small sensor to increase the dynamic range. Instructor: David King

Resolution versus Resolution – Other approaches… SIGMA / FOVEON Foveon was a pioneer of the non-video approach to image sensing and produced one of the very first functioning digital cameras: a Compac™ laptop with a Canon™ lens mount. The Foveon™ chip used in the Sigma cameras uses three stacked RGB filters at each photosite to eliminate interpolation. They claim this gives them a 3X increase in resolution over the actual pixel dimension of the chip. Instructor: David King

The Inevitable Comparisons with Film So what are you giving up to switch or go to Digital? The normal comparisons involve these image factors… Dynamic Range Color Range Detail Tonalities Image Durability Cost and Time Instructor: David King

The Inevitable Comparisons with Film DYNAMIC RANGE This is the range of tones that can be recorded from deep black shadows to bright white highlights. It can be expressed…  in terms of “stops” of exposure, or  in terms of a Density / Gamma range as measured on a densitometer. Instructor: David King

The Inevitable Comparisons with Film DYNAMIC RANGE MEDIA STOPS GAMMA Film: Color Pos /- Film: B&W Neg /- B&W Paper P&S Digital < DSLR* Digital /- High end InkJet Print * High end chips in Digital Backs are better Instructor: David King

The Inevitable Comparisons with Film COLOR RANGE No media can capture the total color range of the human eye. We “See color” visually in RGB but also “feel color” psychologically. High end DSLR is roughly equivalent to Kodak’s Kodachrome Instructor: David King

The Inevitable Comparisons with Film DETAIL and RESOLUTION Film is limited by the lenses and developers. It can theoretically capture finer detail than virtually any lens can resolve because of its microscopic grain. A single grain of VERY FINE GRAINED FILM averages about 2 microns … However… film clumping severely cuts back on this theoretical potential since it takes grains to clump to reveal increments of tonality... High end digital cameras can also capture more than most lenses resolve though not as much more as film’s potential. A Common 6 Mp DSLR’s photosites are about 6 microns. In practice it can resolve finer detail than many films’ grain clumps however because each pixel can create any tone. Instructor: David King

The Inevitable Comparisons with Film DETAIL and RESOLUTION Of course with larger film formats the grain to image size relationship changes but it does so with larger format digital backs as well. So how do formats of film compare? It is commonly felt in the professional world that you can easily match… 35mm with a 6 Mp DSLR 645/6x6 MF with an 8 Mp DSLR 6x7 MF with a 16 Mp DSLR Large Format with a 20+ Mp DSLR or 4-shot digital back Instructor: David King

The Inevitable Comparisons with Film Tonality Rendering (Distinguishing gray tones) Film is binary: random black silver grain clumps and clear (film) or white (paper) blend to create the illusion of tonal increments. Digital is capable of a very fine increment of tones based on the “BIT DEPTH“ of the file. This is a computer specific issue related to the number of “bits” used to define a single tone. Here is the breakdown: Bit Depth # of Luminosity Increments # of RGB Colors million , trillion , trillion Since human vision can only distinguish about 100 increments this should be OK. Instructor: David King

The Inevitable Comparisons with Film Image Durability: How Long will a Print Last? This is the “archival” potential of a final printed image. Answer? Ot Depends… Image Type Potential life span under museum conditions Type “C” Color Print years B&W RC Print years (is improving with new materials) Fuji Crystal Archive Color years B&W Archival Fiber years Normal Inkjet Dyes years (Typical non-photo printer) Photo Quality Dyes years Hybrid/Pigmented Dyes years Pigment Color inks years Carbon Pigment B&W inks years. Instructor: David King

The Inevitable Comparisons with Film Time and Cost After the initial investment in equipment Digital is much faster and cheaper since there is no film and no processing. However for the professional the real competitive advantage is speed On the commercial world, Digital is the primary medium for about 95% of the work shot. Instructor: David King

QUESTIONS? Instructor: David King

Introduction to Digital Photography

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