|
Resolution Values
Video Tape, Printed Hardcopy & 35
mm slides
Video Recording Media (shades of gray)
Typical
Values |
VHS |
SVHS |
Signal
to Noise Ratio (SNR) * |
46db |
47.6db |
Shades
of Gray |
199 |
239 |
luminance
frequency bandwidth
black and white signal |
4.5 MHz |
7.0 MHz |
Number
of Horizontal Lines |
» 300 |
>
400 |
*SNR = 20*log10 [Intensity Max/Intensity Min]
= Definition of db = decibel
SNR = 48.2db = 256 shades of gray;
SNR = Signal to Noise
Ratio
Hardcopy Print Media (shades of gray)
Print Media |
Resolution
lines per inch = lpi
dots per inch = dpi |
Shades of gray |
Printer technology |
| Laser/Ink Jet |
600 dpi |
37.5 |
half tone |
| Laser/Ink Jet |
1200 dpi |
75.0 |
half tone |
| Laser/Ink Jet1 |
2400 dpi |
150 |
half tone |
| Dye sublimination2 |
300 lpi = 4800 dpi |
=»
256 |
continuous
tone |
| 35 mm slides3 |
4000 lines
» 2900 lpi |
=»
2900 |
continuous
tone |
| Laser/Ink Jet4 |
» 2400 |
256 |
half tone |
lpi = dpi/16 for 256 shades of gray
lines per inch = line frequency = dots per
inch ÷ 16 for 256 shades of gray
e.g.,1200dpi /16 = 75 shades of gray, Laser/Ink Jet half tone printing
technology
half tone printing is a box of dots, very small dots either black or white arranged adjacent one another to make a smooth looking image, e.g., laser jet, ink jet, commercial type postscript printers.
continuous tone printing is one dot with adjustable intensity, e.g., dye sublimation printers, computer monitors, televisions monitors, photographs, slides, etc.
16 dots by 16 dots are required to make 256 half tone shade of gray cells. The
half tone cells are combined to construct the image. 0 may be assigned
black with 255 assigned white. 0 is then a full 16 by 16 dot pattern for total black, while 255 is an
empty 16 by 16 dot pattern for total white.
In the above note that a dye sublimation printer does not have 4800 dpi for 256 shades of a color. Dye sublimation printers are not normally referred to as having dpi values. The mention of 4800 dpi is the equivalence that a half tone printer needs in order to do the same job as that
of a 300 lpi continuous tone dye sublimation printer for 256 shades. The only purpose of the mention of 4800 dpi was for comparison of continuous printing to half tone printing.
Printing terminology is a wonderful thing. There is lpi, dpi, ppi, half tone, contone, continuous tone, and then there are dots, pixels, lines, screens, frequency, decibels, shades of gray, etc., not to mention whether
these items are per inch or per millimeter and if they are in millimeter pairs or line pairs per or what ever pairs. The real trick is to understand the basic meaning of all these wonderful descriptions and then never use them in court
1
The Color Scanner Book by Stephen Beale
and James Cavuoto,
ISBN D-0-941845-11-7, Micro Publishing Press 21150 Hawthorne Blvd
Ste 104 Torrance, CA 90503 (310) 371 6787 First Printing May 1995
2
Slide Imagers - Imagers Presentation
Services, Atlanta Tech Center, Bldg 400,
3
35
mm film recorders measure resolution in total lines, TREC’s slides
are made on a 4000 line film recorder by Slide Imagers of Atlanta
4000 lines ÷ 35 mm » 2,903 lines per inch
4 XLI
Corporation Enhanced Laser Jet Printer hardware for HP LaserJets up to version 5 - no longer in production
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