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Understanding Digital Video: Scanning, Aspect Ratios, and Quality Factors

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19 diapositives · 367 Views · Aug 10, 2014

This lecture explores the fundamental differences between Standard Definition Television (SDTV) and High Definition Television (HDTV), focusing on scanning methods, aspect ratios, and resolution quality. It discusses the specifications of 525 lines for SDTV versus 720p and 1080i for HDTV. Key factors affecting video quality, such as frame rate, resolution, and color sampling (4:2:0 vs. 4:4:4), are analyzed. Additionally, technical insights on digital cameras, compression ratios, and shooting techniques for effective visual storytelling are provided, catering to both beginners and advanced filmmakers.

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  1. Lecture Digital Video

  2. Scanning vs. aspect ratio • SDTV • 525 (vertical) res of interlaced scanned lines (actually 300x480) • Aspect ratio of 4:3 • HDTV • Most prevalent: 720p (ABC, Fox) or 1080i (NBC, CBS) • Also 1125, plus 1080 and more (“RED” camera 4900 x 2980 !) • Aspect ratio of 16:9 • 24 p: 24 fps • Refers to frames per second • lines of resolution can be varies: ex, 1920 x 1080, 1280 x 720, 1440 x 1080 • More film-like (do you know why?) • Can generate masters for SD, DV and HD due to its high quality. • HDV: • 16:9 • Both 720p & 1080i

  3. horizontal lines of resolution • This refers to the number of horizontal lines within each frame.  The higher the number– the better the clarity and definition of the picture.

  4. Factors determining file size in DV • Resolution (# pixels) • Frame rate (fps) • Color Depth (bits) See p. 15, ch. 1

  5. Resolution • How SHARP the image is • Determined by the number of pixels seen ACROSS the screen: HORIZONTAL resolution. • Is NOT same as video /TV “scanning” • Horizontal scanning depends on to some degree quality of TV set • The higher the resolution, the better • Standard ANALOGUE TV: 4:3; 640 x 480 • DV: 4:3 or 16:9; • HD & HDV: 1280 x 720 720 (30p;) 1440 x 1080(60i); 1920x 1080i

  6. Compression: • reduces amt of space need to store video data & move across bandwidth • Lossless • Lossy • Codecs • Compression Ratio • Higher the ratio, the more compression allowing more info but also lower quality. • DV/DVCAM: compression of 5:1

  7. Color Sampling • Drop out: loss of signal due to imperfections on tape • Color sampling- also expressed as a ratio • Color sampling is, in effect, a form of compression.  • Luminance (y): color (ry): color (by) • Since the human visual system is much more sensitive to variations in brightness than color, a video system can be optimized by devoting more bandwidth to Y' than the color difference components Cb and Cr. 4:2:0 > two channels of component color info (2) are sampled at half the resolution of the brightness info (4) [every 4 x color is sampled, brightness is sampled twice] 4:4:4 > Full resolution color Every 4x brightness info is sampled, brightness is sampled 4x. • DV standard 4:1:1 • DVCPro50 4:2:2 • Digital S 4:2:2 • HDV 4:2:0 • HD Pro 4:2:2 • “Red” (HD) 4:4:4 (btw: Red’s res = 4900 x 2980!!!)

  8. Digital Cameras • CCD- charge coupled device • CMOS- complementary metal oxide semiconductor chip

  9. chrominance • HUE- actual tint • SITUATION- intensity of color • LUMINANCE - Brightness; degree of lightness & darkness, amt of B & W

  10. SMPTE Time code • 03:45:18:29 Hr :Min: Sec: Frames • Drop frame vs. Non-Drop Frame

  11. Lenses • Focal length: fixed vs. variable (zoom) • Zoom ratio: • 10:1 If widest shot is 20 mm, tightest shot is 200mm • 20X Zoom Makes subject appear 20 times closer than it actually is in reality. • Macro setting: VERY close! Use for tiny subjects (bugs, surgery, how to videos, etc.--for extremely small items w/ extreme close ups.)

  12. Focus • Setting focus • Racking (pulling) focus) • Auto? Or not to auto focus?

  13. aperture • Has adjustable IRIS (diaphragm) • F-stops: f/1.4 wide open), f/22 (smaller) • Slow & fast lenses (more light)

  14. Depth of field • Range of what objects are in sharp focus • Varies: • Aperture (f-stop) • Camera-subject distance (closer the subject, the less DoF • Focal length of lens • Example: The longer the focal length, wider the aperture, shallower the depth of field. • Wide-angle: greater DoF • A lens set at f/22 will create greater DoF than f/2.8

  15. Shot->scene->sequence • Mise-en-scene: • composition • Framing • Basic shots: XCU, CU, MS, LS, XLS • Subjective shots: POV shot, OS • Cam Angle: 5 diff. angles. What are they?

  16. Composing within static frame • Blocking • Balance • Creating depth; z-axis • Rule of thirds • Shot duration: longer on frame affects how audience sees it & understands it • 30 degree rule-avoids jump cuts

  17. Composing for the moving frame • Don’t be afraid to let subject arrive-leave frame • Don’t shoot everything, every moment! • Camera movement • Pan • Tilt • Dolly • Tracking • Crane (boom) • Arc

  18. Shooting multi-cam set upandShooting to Edit • Three basic style of coverage • Classical, contemporary, personal ….See other PPTs on Directing for Form & Content ( : • Shooting for continuity • 180 degree rule-continuity of action • Also, see otherPPTs onDirecting for Form & Content)

  19. Differences between: Standard, DV, HD, Broadcast, Multimedia, Web video. • See chapter 1.