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Small Format HD Acquisition

Small Format HD Acquisition. Part 1 – What’s Out There Part 2 – The Optical Format Factor Part 3 – Hierarchical Analysis. Current Small-Format HD. 4: luma samples BR: bit rate D: DV coding F: fixed lens GOP: group of picture length I: interchangeable lens M: MPEG coding

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Small Format HD Acquisition

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  1. Small Format HD Acquisition • Part 1 – What’s Out There • Part 2 – The Optical Format Factor • Part 3 – Hierarchical Analysis Mark Schubin, HPA Technology Retreat, 2006 February 23

  2. Current Small-Format HD 4: luma samples BR: bit rate D: DV coding F: fixed lens GOP: group of picture length I: interchangeable lens M: MPEG coding /: maximum aperture * all imagers 1/3-inch except Sanyo 1/2.5-inch Panasonic records on P2 card, Sanyo on SD card, all others DV tape Coming soon: Samsung SC-HDX15, Sony HDR-HC3 For about twice the highest price above and somewhat larger size, there are also the Grass Valley Infinity (2/3”) and Sony XDCAM HD (1/2”). Mark Schubin, HPA Technology Retreat, 2006 February 23

  3. Optical Format Factor: The Basics y Ø y Ø Ø x x lens image normal imager widescreen imager imager Ø AR x y S35 31 4:3 24.9 18.7 1-inch 16 4:3 12.8 9.6 1-inch 16 16:9 13.9 7.8 2/3-inch 11 4:3 8.8 6.6 2/3-inch 11 16:9 9.6 5.4 1/2-inch 8 4:3 6.4 4.8 1/2-inch 8 16:9 7.0 4.0 1/3-inch 6 4:3 4.8 3.6 1/3-inch 6 16:9 5.2 2.9 Mark Schubin, HPA Technology Retreat, 2006 February 23

  4. The Format Factor Divide equivalent factors of one format by another’s. e.g., 2/3-inch imager 11-mm diagonal divided by 1/3-inch imager 6-mm diagonal yields a format factor of 1.83. Mark Schubin, HPA Technology Retreat, 2006 February 23

  5. Acceptance Angle O I – = – D F • Based on focal length and imager size: • 13.5 mm lens, 16:9 aspect ratio, horizontal: • 55° – 1-inch (wide angle) – 10.3’ shot at 10’ • 39° – 2/3-inch (normal) – 7.1’ shot at 10’ • 29° – 1/2-inch (tighter) – 5.2’ shot at 10’ • 22° – 1/3-inch (tighter still) – 3.9’ shot at 10’ I O D F Mark Schubin, HPA Technology Retreat, 2006 February 23

  6. Applying the Format Factor • 13.5-mm lens in 2/3-inch format divided by 1.83 yields 7.4-mm lens in 1/3-inch format for equivalent acceptance angle. • 4.8-mm lens in 2/3-inch format yields 2.6-mm lens in 1/3-inch format, but that focal length is not available in that format. Failure of the Format Factor Mark Schubin, HPA Technology Retreat, 2006 February 23

  7. Sensitivity • Based on individual sensor (not imager) size: • Range of 1/3-inch sensor (“pixel”) sizes: • 2/3-inch comparison: full output 1/4 output 960 x 540 1920 x 1080 1440 x 1080 960 x 1080 1280 x 720 2/3-inch 1920 x 1080 2/3-inch 1280 x 720 Mark Schubin, HPA Technology Retreat, 2006 February 23

  8. Applying the Format Factor • For equivalent H & V resolutions, f/4in 2/3-inch format divided by 1.83 yields f/2.2 for equivalent sensitivity. • f/1.8 in 2/3-inch format yields f/1in 1/3-inch, but that aperture is not available. • Dynamic range is proportional to sensor size, so even wider apertures are limited. Failures of the Format Factor Mark Schubin, HPA Technology Retreat, 2006 February 23

  9. Depth of Field • Range of distances appearing to be in focus with the lens focused at some particular distance • Complex equations based on f-stop*, focal-length*, shooting distance, and “circle of confusion*” (visually indistinguishable from a dot) * format-factor-related Mark Schubin, HPA Technology Retreat, 2006 February 23

  10. Depth of Field • Less allows attention direction • Is more DOF better for news? Mark Schubin, HPA Technology Retreat, 2006 February 23

  11. Applying the Format-Factor • At DoF-related distances*, for same viewed resolution & framing, DoF is that of a different format with the f-number and focal length adjusted by the format factor: • 2/3-inch 14.6-mm f/3.3 = 1/3-inch 8-mm f/1.8 * not macro, not in the hyperfocal range • 2/3-inch 6-mm f/1.8 = 1/3-inch 3.3-mm f/1, which is not available Failure of the Format-Factor Mark Schubin, HPA Technology Retreat, 2006 February 23 *except microlens aperture issue

  12. Introducing Contrast Do you see a curve across the top? Mark Schubin, HPA Technology Retreat, 2006 February 23

  13. Modulation Chart contrast resolution Mark Schubin, HPA Technology Retreat, 2006 February 23

  14. Modulation Chart contrast curve varies with retinal angle and observer resolution Mark Schubin, HPA Technology Retreat, 2006 February 23

  15. Modulation Transfer Function curve shape varies due to such factors as filtering, diffraction, etc. contrast “sharpness” is proportional to the square of the area under the curve resolution Mark Schubin, HPA Technology Retreat, 2006 February 23

  16. Combining Vision & Technology contrast not reproduced available & visible invisible resolution Mark Schubin, HPA Technology Retreat, 2006 February 23

  17. Understanding Diffraction Airy disk MTF reduced, resolution unaffected Mark Schubin, HPA Technology Retreat, 2006 February 23

  18. Diffraction and MTF • Monochromatic diffraction-based MTF • MDMTF = 1 - (1.22 x λ x f x lp/mm) • For diffraction-limited resolution: • MDMTF = 0 • Rayleigh Criterion: Airy disks one radius apart 100% MTF almost 100% MTF Mark Schubin, HPA Technology Retreat, 2006 February 23

  19. Violating the Rayleigh Criterion Canon EOS 20D – 6.4 µm sensor pitch f/8 f/11 f/16 f/22 originals 232 x 173 Mark Schubin, HPA Technology Retreat, 2006 February 23

  20. f/8 (f/3.4) f/11 (f/4.6) (1080-HD 1/3-inch equivalent) f/16 (f/6.7) f/22 (f/9.3) Mark Schubin, HPA Technology Retreat, 2006 February 23

  21. Diffraction & the Format Factor 92% • Diffraction rarely significant in SDTV • Format factor applies f-number at MTF: 0%50%75% • 2/3” 1088 pels/line--- 22.9 11.55.7 • 2/3” 1920 pels/line --- 13.0 6.5 3.3 • 1/3” 1920 pels/line --- 7.1 3.51.8 • 2/3” 1920 pels/line --- 20.5 10.2 5.1 • 1/3” 1920 pels/line --- 11.2 5.6 2.8 100% worst-case: λ = 630 nm (red) best-case: λ = 400 nm (blue) Mark Schubin, HPA Technology Retreat, 2006 February 23

  22. Lens Characteristics vs. F-stop nota video lens or camera • Lower f-stop: less diffraction, more sensitivity • Higher f-stop: less aberrations, ghosts, flare, vignetting, better relative light distribution • Sweet-spot: 2-3 stops below maximum open • simple-lens aberrations reduced in smaller formats • Do lens corrections result in the 2-3 rule of thumb? • If so, small formats may lack the sweet spot. Canon EF75-300/4-5.6 IS 300-mm closest focus, shot on EOS 20D Mark Schubin, HPA Technology Retreat, 2006 February 23

  23. Lens Quality & the Format Factor • Lens MTF often uses line-pairs/millimeter (lp/mm) as the resolution axis • Smaller formats have fewer mm so higher lp/mm at equivalent image resolution and, therefore, need higher-quality lenses for equivalent MTF • 100 lp/mm in 2/3-inch format x 1.83 format-factor yields 183 lp/mm in 1/3-inch Mark Schubin, HPA Technology Retreat, 2006 February 23

  24. Relative MTF of HDTV and SDTV 2/3-Inch Studio Lens Measured at Picture Center Wide-angle @ F-4.0 16:9 5.5 MHz SDTV Band-edge 1080/60i HDTV Band-edge Optical Reference 100 HDTV From “The Central Role of the lens in HDTV Imaging,” Laurence Thorpe, Canon, PBS Technology Conference 2005 SDTV MTF % LP/mm Line-Pairs per Millimeter 20 40 60 80 56 Mark Schubin, HPA Technology Retreat, 2006 February 23

  25. Format-based Lens MTF Points 2/3-inch SDTV 544 lp in 9.6 mm ≈ 57 lp/mm (30) 1-inch HDTV 1035 960 lp in 13.9 mm ≈ 69 lp/mm (56) 2/3-HDTV 720 640 lp in 9.6 mm ≈ 67 lp/mm 2/3-HDTV 1080 960 lp in 9.6 mm = 100 lp/mm (81) 100 B&H Photo Prices: Canon XL H1 HDV cc w/20x lens - $ 9K Canon J17Ex7.7BIRS 2/3” lens - $11.5K Canon HJ17Ex7.7B 2/3” HD lens- $19K (not from B&H and much older): Canon HV12x12 1-inch HD lens-$112K “HDTV” 184/100 ≈ 2/3-to-1/3 format factor MTF % “SDTV” 1/3-inch 720 640 lp in 5.2 mm ≈ 122 lp/mm 1/3-inch 1080 960 lp in 5.2 mm ≈ 184 lp/mm (149) 1/2-XDCAM HD 960 lp in 7.0 mm ≈ 138 lp/mm (110) 1/3-inch SDTV ~427 lp in 5.2 mm ≈ 82 lp/mm (55) LP/mm Line-Pairs per Millimeter 20 40 60 80 Mark Schubin, HPA Technology Retreat, 2006 February 23

  26. Conclusions • The format factor allows conversion of focal length, aperture, and depth of field between formats, but it fails when the limits of the lens/prism are reached. • Dynamic range is based on sensor area. • Lenses for smaller-format cameras need to be better than lenses for larger-format cameras, by the format factor, for equivalent MTF. • And, now, heeeeeeere’s Larry! Mark Schubin, HPA Technology Retreat, 2006 February 23

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