Color bars (a.k.a. color command bars, color command strips, or proofing bars) are essentially seek out targets that are used to stair out impress and/or proof attributes. Normally, but non always, it is printed inwards the cut surface area of the press sheet.
Typical placement of a color bar on an offset press canvass - at the trailing border (back halt of the sheet).
However, it tin convey many different forms - sometimes difficult to recognize - but e'er serving the same purpose.
Sometimes the "color bar" is incorporated inside the graphic pattern of the publication. In this instance the color makeup of the championship (Cyan) together with department headers (Blue, inwards this example, - Magenta overprinting Cyan).
Sometimes it is hidden inwards the spine (in this instance the grayness trace running from plough over to bottom on the front end border of the photo).
While it is sure possible to stair out the color of the actual alive icon area, the applied scientific discipline is expensive and, every bit result, few printers are fortunate plenty to receive got it at their disposal. Also, measuring the alive icon surface area doesn't supply every bit much useful information every bit a color bar can. Color bars thence human action every bit proxies, or substitutes, for the alive icon surface area too every bit supply additional data.
The logic behind color bars
1) Unlike the alive icon surface area of the press sheet, color bars are consistent project to job. Therefore they are to a greater extent than efficient at providing a benchmark together with tin survive used to rail trends inwards variation over time.
2) Color bars tin survive tailored to run into the needs together with measure capabilities of private impress shops.
3) Color bars may survive used to stair out all aspects of the "print characteristic" - company ink density, overprinting (ink trapping), dot gain, grayness balance, too every bit issues such every bit slur together with dot doubling.
4) Color bars tin unwrap issues alongside ink hue, blanket condition, impression cylinder pressure, etc.
5) They tin survive used forensically to aid sympathise why a specific project did non run into expectations.
6) They are efficient since, different the alive icon area, they are a constant made upwards of good defined elements that maintain from proof to press sheet.
Solid ink density
Influenza A virus subtype H5N1 printing press is essentially a complex machine for laying downwardly a specific cinema thickness of a specific color of ink onto a substrate. The ink is metered out inwards zones across the width of the press canvass according to how much ink coverage is required for each color inwards each zone.
Therefore, for most press operators, the minimum requirement for a color bar is that it contains company patches of the inks that volition survive printing since company ink density is the exclusively affair on press that an operator tin conform piece the press is running.
Those company patches are so repeated over the width of the press canvass so that each ink zone is represented past times at to the lowest degree i consummate ready of patches - containing i field for each color beingness printed.
Information provided past times exclusively using company ink density targets inwards the color bar
In this example, cyan is misregistered piece the dark printer is over emulsified (fountain solution breaking downwardly the ink).
1) Provides a company ink density value, measured using a densitometer, to create upwards one's remove heed if the press canvass is conforming to published industry, or store specific targets.
2) Is an indirect, but practical, method of determining optimum ink cinema thickness together with hence the residual of maximum color gamut without introducing icon degrading inking issues such every bit slinging/misting.
3) The residual of the master copy company densities determines the hue of the overprints - i.e. the SID of magenta together with SID of yellowish create upwards one's remove heed the hue of the resulting red.
4) Indicate misregistration which tin so survive examined inwards the alive icon area.
5) Reveal defects such every bit slinging/misting/tailing, over emulsification, slur, doubling.
6) If records are kept, the hue of the ink currently on press compared alongside the hue of ink used inwards the past times to create upwards one's remove heed if at that spot is whatever contamination, alter inwards color due to ink batch differences, etc.
Forensic targets on color bars are icon elements that are typically non measured past times the press operator unless at that spot is a work inwards aligning presswork to the proof. If that happens so these targets may supply useful information every bit to the crusade of the problem.
Two-color overprint ink trapping targets
Ink "trap" is an objective indication of the ability, or inability, of a printed ink to receive got the following ink printed compared alongside how good the substrate accepted that ink. Poor ink trapping results inwards presswork color shifts inwards reds (magenta plus yellow), greens (cyan plus yellow), together with blues (cyan plus magenta) too every bit a loss inwards total color gamut.
The two-color overprint solids allows for the objective measure together with evaluation of ink trap efficiency too every bit the overprint hue fault together with greyness.
Typical trap values for 3 impress weather running a CMY ink sequence alongside Black showtime or final down:
Offset sheetfed: R=70, G=80, B=75
Heatset spider web offset (publications): R=70, G=87, B=72
Coldset spider web offset (newspaper): R=50, G=89, B=50
Slur together with doubling targets
Slurring together with doubling are impress defects that occur when halftone dots together with type blur every bit a termination of a slight minute contact or motility betwixt press cylinders or the paper together with blanket. (More well-nigh slur HERE together with doubling HERE)
There are many different styles of slur together with doubling detection targets. Here are 2 of the most popular:
Of course, every halftone dot or missive of the alphabet grapheme on the printed canvass volition unwrap slur together with doubling, all the same the targets inwards the color bar signal the defect easier together with quicker.
Grey residual targets
Grey residual targets are made upwards of a field of 3 screened procedure colors that are balanced so every bit to look every bit neutral grayness nether measure printing conditions. They are typically printed side past times side to a dark covert tint of a similar value to allow for a quick visual, or measured, evaluation of how grayness residual has shifted.
Grey residual targets tin survive useful since variation inwards whatever of the 3 procedure colors because of dot gain, slur, doubling, density, trapping, together with registration volition survive reflected past times a shift inwards hue away from neutrality. The 3/C field volition convey on a bluish, reddish, or greenish color cast.
The persuasion behind this target is that whatever grayness residual color shift away from neutrality suggests a possible color shift inwards the alive icon area. However, inwards production printing the grayness residual target may non survive a reliable indicator of presswork issues.
Other targets
Other targets that may survive included inwards the color bar are:
Dot gain
These targets are intended to capture dot gain variation information. The dot gain targets may consist of only 2 patches for each procedure color to stair out the dot gain a i location on the note scale, or, alongside the add-on of to a greater extent than patches, to stair out the dot gain at the quarter, mid, together with three-quarter note values. Dot gain tin survive useful because issues similar slur, doubling, or wrong company ink density, volition survive reflected past times a variation inwards the measured dot gain.
Brown residual targets
Brown residual patches are similar to grayness residual patches inwards role except that they are made upwards equal percentages of cyan, magenta, together with yellow. Unlike grayness residual patches which allow the press operator to construct a subjective visual assessment of hue shift, chocolate-brown residual patches tin exclusively survive evaluated objectively alongside instruments.
Proprietary
Proprietary targets such every bit that used past times System Brunner are typically used to drive on-press unopen loop color command systems.
Spot color
If a spot or construct color is beingness used so it volition warrant at to the lowest degree a company field inwards the color bar so that its company ink density tin survive measured. Space permitting, the company field volition survive side past times side to a screened dorsum field so that dot gain information tin survive measured.
For procedure control, color bars should survive included on every proof together with press aeroplane of every job. If that is non possible because at that spot is no room on the canvass (as oftentimes happens inwards paper work) so at that spot are several options;
1) Run color bars on occasion past times including it inwards the alive icon area.
With the publisher's permission if required.
2) With the impress buyer's permission, contain color bars seek out elements into the graphic/editorial pattern of the printed slice (see the USA Today instance inwards Part 1).
Color bars are non a requirement for character printing, however, they are fundamental to making proofing together with printing to a greater extent than efficient together with effective piece reducing overall production costs.
Presswork should survive run "to the numbers" i.e. the company ink density aim points, at which fourth dimension the presswork should align to the signed-off proof. At that quest the press operator should survive gratis to construct whatever needed ink fundamental adjustments to refine the match. The color bar so becomes a tape of initial correspond together with needed adjustments. That information tin survive used inwards statistical procedure command to spot whatever trends, or issues, revealed past times the form of ink fundamental moves that are made over time.
Color bars tin survive placed anywhere that they fit on the press form, including the atomic number 82 together with trailing border too every bit across the catch of the form. In fact, placing it inwards the catch of the aeroplane parallel to the inking rollers is ideal, since at that spot is less likelihood of seeing the variation that occurs at the atomic number 82 together with trailing edges. Color bars tin fifty-fifty survive placed inwards the gutter inline alongside the direction of the canvass through the press, although doing so is non optimal since it provides information from exclusively i ink fundamental zone.
Ideally the color bar should exercise the same halftone screening every bit the alive icon surface area together with receive got had the same press flexure applied.
However, it tin convey many different forms - sometimes difficult to recognize - but e'er serving the same purpose.
While it is sure possible to stair out the color of the actual alive icon area, the applied scientific discipline is expensive and, every bit result, few printers are fortunate plenty to receive got it at their disposal. Also, measuring the alive icon surface area doesn't supply every bit much useful information every bit a color bar can. Color bars thence human action every bit proxies, or substitutes, for the alive icon surface area too every bit supply additional data.
The logic behind color bars
1) Unlike the alive icon surface area of the press sheet, color bars are consistent project to job. Therefore they are to a greater extent than efficient at providing a benchmark together with tin survive used to rail trends inwards variation over time.
2) Color bars tin survive tailored to run into the needs together with measure capabilities of private impress shops.
3) Color bars may survive used to stair out all aspects of the "print characteristic" - company ink density, overprinting (ink trapping), dot gain, grayness balance, too every bit issues such every bit slur together with dot doubling.
4) Color bars tin unwrap issues alongside ink hue, blanket condition, impression cylinder pressure, etc.
5) They tin survive used forensically to aid sympathise why a specific project did non run into expectations.
6) They are efficient since, different the alive icon area, they are a constant made upwards of good defined elements that maintain from proof to press sheet.
Solid ink density
Influenza A virus subtype H5N1 printing press is essentially a complex machine for laying downwardly a specific cinema thickness of a specific color of ink onto a substrate. The ink is metered out inwards zones across the width of the press canvass according to how much ink coverage is required for each color inwards each zone.
Therefore, for most press operators, the minimum requirement for a color bar is that it contains company patches of the inks that volition survive printing since company ink density is the exclusively affair on press that an operator tin conform piece the press is running.
Those company patches are so repeated over the width of the press canvass so that each ink zone is represented past times at to the lowest degree i consummate ready of patches - containing i field for each color beingness printed.
Information provided past times exclusively using company ink density targets inwards the color bar
1) Provides a company ink density value, measured using a densitometer, to create upwards one's remove heed if the press canvass is conforming to published industry, or store specific targets.
2) Is an indirect, but practical, method of determining optimum ink cinema thickness together with hence the residual of maximum color gamut without introducing icon degrading inking issues such every bit slinging/misting.
3) The residual of the master copy company densities determines the hue of the overprints - i.e. the SID of magenta together with SID of yellowish create upwards one's remove heed the hue of the resulting red.
4) Indicate misregistration which tin so survive examined inwards the alive icon area.
5) Reveal defects such every bit slinging/misting/tailing, over emulsification, slur, doubling.
6) If records are kept, the hue of the ink currently on press compared alongside the hue of ink used inwards the past times to create upwards one's remove heed if at that spot is whatever contamination, alter inwards color due to ink batch differences, etc.
Forensic targets on color bars are icon elements that are typically non measured past times the press operator unless at that spot is a work inwards aligning presswork to the proof. If that happens so these targets may supply useful information every bit to the crusade of the problem.
Two-color overprint ink trapping targets
Ink "trap" is an objective indication of the ability, or inability, of a printed ink to receive got the following ink printed compared alongside how good the substrate accepted that ink. Poor ink trapping results inwards presswork color shifts inwards reds (magenta plus yellow), greens (cyan plus yellow), together with blues (cyan plus magenta) too every bit a loss inwards total color gamut.
The two-color overprint solids allows for the objective measure together with evaluation of ink trap efficiency too every bit the overprint hue fault together with greyness.
Typical trap values for 3 impress weather running a CMY ink sequence alongside Black showtime or final down:
Offset sheetfed: R=70, G=80, B=75
Heatset spider web offset (publications): R=70, G=87, B=72
Coldset spider web offset (newspaper): R=50, G=89, B=50
Slur together with doubling targets
Slurring together with doubling are impress defects that occur when halftone dots together with type blur every bit a termination of a slight minute contact or motility betwixt press cylinders or the paper together with blanket. (More well-nigh slur HERE together with doubling HERE)
There are many different styles of slur together with doubling detection targets. Here are 2 of the most popular:
Of course, every halftone dot or missive of the alphabet grapheme on the printed canvass volition unwrap slur together with doubling, all the same the targets inwards the color bar signal the defect easier together with quicker.
Grey residual targets
Grey residual targets are made upwards of a field of 3 screened procedure colors that are balanced so every bit to look every bit neutral grayness nether measure printing conditions. They are typically printed side past times side to a dark covert tint of a similar value to allow for a quick visual, or measured, evaluation of how grayness residual has shifted.
Grey residual targets tin survive useful since variation inwards whatever of the 3 procedure colors because of dot gain, slur, doubling, density, trapping, together with registration volition survive reflected past times a shift inwards hue away from neutrality. The 3/C field volition convey on a bluish, reddish, or greenish color cast.
The persuasion behind this target is that whatever grayness residual color shift away from neutrality suggests a possible color shift inwards the alive icon area. However, inwards production printing the grayness residual target may non survive a reliable indicator of presswork issues.Other targets
Other targets that may survive included inwards the color bar are:
Dot gain
These targets are intended to capture dot gain variation information. The dot gain targets may consist of only 2 patches for each procedure color to stair out the dot gain a i location on the note scale, or, alongside the add-on of to a greater extent than patches, to stair out the dot gain at the quarter, mid, together with three-quarter note values. Dot gain tin survive useful because issues similar slur, doubling, or wrong company ink density, volition survive reflected past times a variation inwards the measured dot gain.Brown residual targets
Brown residual patches are similar to grayness residual patches inwards role except that they are made upwards equal percentages of cyan, magenta, together with yellow. Unlike grayness residual patches which allow the press operator to construct a subjective visual assessment of hue shift, chocolate-brown residual patches tin exclusively survive evaluated objectively alongside instruments.Proprietary
Proprietary targets such every bit that used past times System Brunner are typically used to drive on-press unopen loop color command systems.Spot color
If a spot or construct color is beingness used so it volition warrant at to the lowest degree a company field inwards the color bar so that its company ink density tin survive measured. Space permitting, the company field volition survive side past times side to a screened dorsum field so that dot gain information tin survive measured.For procedure control, color bars should survive included on every proof together with press aeroplane of every job. If that is non possible because at that spot is no room on the canvass (as oftentimes happens inwards paper work) so at that spot are several options;
1) Run color bars on occasion past times including it inwards the alive icon area.
With the publisher's permission if required.2) With the impress buyer's permission, contain color bars seek out elements into the graphic/editorial pattern of the printed slice (see the USA Today instance inwards Part 1).
Color bars are non a requirement for character printing, however, they are fundamental to making proofing together with printing to a greater extent than efficient together with effective piece reducing overall production costs.
Presswork should survive run "to the numbers" i.e. the company ink density aim points, at which fourth dimension the presswork should align to the signed-off proof. At that quest the press operator should survive gratis to construct whatever needed ink fundamental adjustments to refine the match. The color bar so becomes a tape of initial correspond together with needed adjustments. That information tin survive used inwards statistical procedure command to spot whatever trends, or issues, revealed past times the form of ink fundamental moves that are made over time.
Color bars tin survive placed anywhere that they fit on the press form, including the atomic number 82 together with trailing border too every bit across the catch of the form. In fact, placing it inwards the catch of the aeroplane parallel to the inking rollers is ideal, since at that spot is less likelihood of seeing the variation that occurs at the atomic number 82 together with trailing edges. Color bars tin fifty-fifty survive placed inwards the gutter inline alongside the direction of the canvass through the press, although doing so is non optimal since it provides information from exclusively i ink fundamental zone.
Ideally the color bar should exercise the same halftone screening every bit the alive icon surface area together with receive got had the same press flexure applied.
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