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Digital Imaging By Dr. Philip Lawson FRPS DPAGB

Digital Imaging By Dr. Philip Lawson FRPS DPAGB. By Philip Lawson. Digital Imaging. The Basics - Scanning and Printing The Master Image Working with Layers Working with Channels Black and White. Digital Imaging 1. The Basics - Scanning and Printing The Master Image

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Digital Imaging By Dr. Philip Lawson FRPS DPAGB

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  1. Digital Imaging By Dr. Philip LawsonFRPS DPAGB By Philip Lawson

  2. Digital Imaging The Basics - Scanning and Printing The Master Image Working with Layers Working with Channels Black and White

  3. Digital Imaging 1 The Basics - Scanning and Printing The Master Image Working with Layers Working with Channels Black and White

  4. Luminosity Resolution Colour The Basics

  5. Infinitely Bright No Light Light • In the real world, Luminosities range from:

  6. Bright EV 17 1 EV = x 2 Dark EV 5 Light meter • The light meter can only measure a middling range of Luminosities:

  7. Max Min High Key 1 Film Emulsion • The Film Emulsion can record only a narrower range of Luminosities7 Evs to 9 EVs

  8. 2 Film Emulsion • But it is our choice which range to expose on Max Min Low Key

  9. 3 Film Emulsion • If the film stock has a dynamic range of 7 EVs it has a tonal range of 27 = 128 levels • If the film stock has a dynamic range of 8 EVs it has a tonal range of 28 = 256 levels • If the film stock has a dynamic range of 9 EVs it has a tonal range of 29 = 512 levels

  10. Film Scanners • The Film Scanner converts these into Numbers in the range 0 -255 255 128 0 • It might not be able to record the full range of Film Luminosities

  11. Print Scanners • The Print Scanner suffers in that it • Is scanning a print that already has a reduced luminosity range • Is scanning the print by reflection 255 128 0

  12. The Monitor 1 • The monitor, being a light source is capable of a large dynamic range 255 128 0

  13. The Monitor 2 • This is adjustable via: • Brightness • Contrast • Gamma all of which must be calibrated, set and never again adjusted for consistent results.

  14. The Print • The Print, being a reflective medium is only as bright as the base paper and the light source • And as dark as the minimum reflectance

  15. Luminous Range • Strive to retain the highest range of luminosities at EACH conversion.

  16. Luminous Range • Transparent Film has a higher latent DMAX than Print, so use a FILM SCANNER, min DMAX = 3.6 • Use the best image sources • IF possible scan to 16-bit greyscale and retain for a.l.a.p. • Ensure scanner settingsdeliver a histogram showing even distribution over the full range.

  17. Caution • Care when modifying the image • BRIGHTNESS • CONTRAST • A pixel cannot be brighter than 255 • Burn out • A picture cannot possess a greater dynamic range than 256

  18. Infinitely Bright No Light Colour • In the real world, Colour is absolute and of infinite variation • Each Primary R, G & B, may be thought of as a Colour Luminosity and follows similar degradation

  19. Colour Gamut • The Gamut of visible colours is described by the LAB space in the Chromaticity diagram

  20. Max Min Film Emulsion • Film Emulsions record colour differently (CYM) • Manufacturer/Stock • Reciprocity Failure

  21. Film Gamut • The Gamut of the Film Emulsion is described by the EKTA space in the Chromaticity diagram

  22. 255 128 0 255 128 0 255 128 0 Film Scanners • The Film Scanner converts Red, Green and Blue into Numbers in the range 0 - 255

  23. 255 128 0 255 128 0 255 128 0 The Monitor 1 • The monitor, being a light source is capable of a large dynamic range

  24. 255 128 0 255 128 0 255 128 0 The Monitor 2 • Provided that you’ve got it set right!

  25. The Monitor 3 • 256 Colours or “High Colour (16-bit)” will give you a Posterised representation • Must use “High Colour (24-bit)”

  26. Monitor (RGB) Gamut • The Gamut of the Monitor is described by the RGB space in the Chromaticity diagramNote the mismatch

  27. Your Phosphors and selected colour temperature The Monitor 4 • However the colour that you get is influenced by:

  28. Your Gammasettings The Monitor 5 • However the colour that you get is influenced by:

  29. The Monitor 6 • However the colour that you get is influenced by: • Your Profiles

  30. The Monitor 7 • The colour that you SEE is influenced by: • Any funny desktop coloursor artificial light

  31. The Programperforms the RGB -> CYMKTranslation The Print • The Print, being a reflective medium has Cyan, Yellow and Magenta translucent inks applied

  32. Print (CYMK) Gamut • The Gamut of the Printer is described by the CMYK space in the Chromaticity diagramAlthough this is very dependant upon the light under which it is viewed

  33. Colour Range • Whilst modifying colour balance, ensure that you do not create an OUT OF GAMUT colour

  34. The Printer 1 • The Printer makes numerous Necessary and Unnecessary Corrections • Colour Space

  35. The Printer 2 • The Printer makes numerous Necessary and Unnecessary Corrections • Transferand • Bleed

  36. The Printer 3 • The Printer makes numerous Necessary and Unnecessary Corrections • Mode

  37. The Printer 4 • The Printer makes numerous Necessary and Unnecessary Corrections • Quality • Media • Halftoning • Adjustment

  38. The Printer 5 • Basic Advice • Print at highest Quality (1440 dpi) • Select the Correct Media Type • Use “Error Diffusion” Halftoning • Use “Photo-realistic” Colour Adjustment • Not “Automatic”!!

  39. MonitorICC Profile ScannerICC Profile PrinterICC Profile Kodak CDICC Profile Characterisation • Colour Management requires each device to be Characterised (by an ICC Profile)

  40. Profiles • Each Device is Characterised by a PROFILE that in turns needs Calibration

  41. Your Gammasettings for the Monitor Calibration Calibration requires • Consistent Conditions • A Known Calibration Source

  42. Profiles • Photoshop manages your Profiles

  43. Colour Range • Use a scanner that Optimises the dynamic range of each colour independently. • Colour Casts can easily be eliminated • Take care when modifying the image • BRIGHTNESS • CONTRAST • Ink is not permanent. Protect from extreme light sources and Save data files.

  44. Resolution • In the real world, the resolution that we achieve is governed by: • Focus • Resolving power of lens • Camera Shake • Heat Haze

  45. Film Emulsion • The Film Emulsion is limited by the clumping of the grains. • Typical Resolving power is <50 lpmm Max = 1750 lines 24mm 35mm

  46. Film Scanners • Typical Film Scanners can detect 2700 d.p.i. • This is sharper than the finest level of detail but not enough to see the individual grains. Max = 4000 pixels 24mm 35mm

  47. Print Scanners • Typical Print Scanners can detect 600 d.p.i. • On a 5” x 7” Printthis would produce4200 pixels and a38Mbyte file. Max = 4200 pixels 5” 7”

  48. The Monitor 1 • The monitor resolution can be a number of prescribed settings LESS than the number of Phosphor dots on the screen. • Choose the highestas this gives youmore desktopspace for all thosepalettes

  49. The Monitor 2 • Always Zoom In or Out and Pan around. • Learn to use the quick keys: • Ctl-0 • Z followed bydrag a rectangle • Ctl + drag a rectanglein the Navigator • Space Bar

  50. The Monitor 3 • NEVER change the Image Size down • This throws vital information away!

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