Archive for the ‘INK’ Category

Color reflection densitometers such as Ihara R730 are equipped with  color filters to deliver density values for the specific process colors Cyan, Magenta, Yellow and Black. For each of the colors Cyan, Magenta and Yellow a specific filter is used which reflects the spectral characteristics of the respective ink.

Fig. 1 shows the remission curves of the solid tones of Cyan, Magenta, Yellow and for Paper White. Remission is the term for the degree of reflectance at a certain wavelength. The remission curve describes the reflectance among the entire visible spectrum and is a unique description for the color.

Fig. 1: The remission curves of the process colors Cyan,Magenta and Yellow and for Paper White.

The solid (optical) density is linear to the amount of ink applied and therefore a valid method for controlling the quality of printwork. Depending on the solid density, the shape of the remission curve changes. As seen in an example in Fig. 2 for three different densities in Cyan the changes are the largest at remission values beyond 590 nm (red).

This is why densities for Cyan are measured with a red filter with a spectral transmittance peak at 600 nm. The Cyan sensor (which consists of a photoelement with a red-sensitive filter in front) just detects the red portion of light and will be susceptible to small changes in Cyan density.

Fig. 2: Example for the remission curves for different densities for Cyan. The density measurement is carried out with a red filter, where changes in remission are susceptible.

Respectively, Yellow is measured with a blue filter at 430 nm and the process color Magenta is measured with a green filter at 530 nm wavelength.  Each process color is detected with its complementary filter:

• Cyan with a red filter

• Magena with a green filter

• Yellow with a blue filter.

The black color could be measured with any (or with no) filter, because its remission is even along the entire spectrum. To achieve a standardized density value, a filter called V is used which reflects the visual gray sensitivity.

 About Ihara R730:

 The Ihara R730 Colour Reflection Densitometer is a sophisticated QC tool. It has all of the measuring functions possible with a densitometer for full analysis of process work.

For a sophisticated densitometer with every possible function for measuring process work, then you need the Ihara R730 – you won’t find better value or a more accurate instrument! Simple operation means it is still fine for basic press control, but the extra features will help you detect and sort out just about anything that can possibly go wrong!

Not only does the R730 allows you to measure tints, and enable you to achieve a consistent ink densities on press, but the wide range of measuring functions available is ideal for QC departments, as well as sorting out printing problems.

  • Top Performance & Reliability  Made in Japan by Ihara Electronic Industries, the R730 has proven reliability and accuracy.
  • Menu Driven Commands  Simply select the required functions from the on-screen menu – you won’t ever need to read a manual. Clear and precise instructions for every measurement are displayed on the large LCD screen.
  • Help Key  Displays explanations for all measuring functions, along with answers to FAQs.
  • Quick Calibration  Recalibrate the unit in seconds.
  • Auto Function  Automatically measures density or dot gain.
  • Printer & Computer Interface  Configurable RS 232 serial interface provided for connecting to a PC or printer.
  • Fully Portable  Rechargeable batteries provide up to 4,000 readings before recharging.
  • Plate Reading  Optimized function for checking control strip tints on plates – available at small extra cost.
  • Filter/Aperture Options  Standard models supplied with Status T filters, 3 mm aperture and polarized. Manufacturer’s options available for Status E filters, 1.7 mm aperture and no polarization.

    Ihara Densitometer R730 – The best in class

Create a new calibration set and higher density calibration target

In order to accurately calibrate the printer and achieve the largest available gamut, a new calibration set should be created. From the Fiery Calibrator choose “Manage…” on the Calibration Set pull down.

Fill out the Recommended Paper field with your media (EFI Laser Proof Paper XF130 Semimatt) and set the Halftone Mode pull down to “175 Line + Fine Text (1200dpi)”. Save the new calibration set with a descriptive name (“EFI XF130 175Line” for example), and choose “Fiery Pro C751- C651 Coated-Glossy v1RF” as the Output Profile. A new calibration set and output profile will be created, “Fiery ProC751-C651 Coated-Glossy v1RF (<new calibration set name>)”.

From CommandWorkstation : Device Center : Resources : Profiles : Output Profiles select the newly created profile, and click the Edit : Color Editor… button. Edit the % Density : D-Max values to the following: C = 1.75, M = 1.50, Y = 1.01, K = 1.80. Save the edited output profile with a descriptive name (“EFI FX130SM 175Line Edited Goal” for example).

Set the edited output profiles as the default in Command WorkStation : Device Center : Color Setup :Color Management : Expert Settings… : Output : Default output profile. Additionally, be sure that “Use media defined profiles if available” is turned off (unchecked).

Warm-up printer and calibrate

The printer should first be in a warmed-up state before proceeding with calibration and characterization. Print, measure, and apply, calibration for the newly created “EFI XF130 175Line” calibration set, utilizing the Fiery Calibrator. It is recommended to use the EFI Spectrometer ES-1000 method, choosing the 34 Sorted Patches page type. Printing 5 or more number of copies, selecting the last for measurement.

Measurements can be inspected in the Fiery Calibrator, by pressing the View… button, with the “Measurement vs. Target” option selected. If the D-max values of the target are not being achieved, it may be necessary to access “Adjustment Settings for Skilled Operators” through the Pro C751’s LCD control panel. Increasing the values in function #0203 “Adjust Maximum Image Density” or #0205 “Adjust Density Difference Across Feed Direction” can have a positive effect on the D-max printed (measured in the Calibrator). It is important to open and close the main panel door on the Pro C751 after adjustment, and to rerun Fiery calibration, checking that target densities have been achieved or exceeded.

Create an output profile

Utilizing Fiery Color Profiler Suite print profiling patches. Be sure in Calibration Setup that “Use current calibration” is selected. Instrument EFI ES-1000 or EFI ES-1000 with iO table can be used. The PageLayout : 1617 random (CGATS IT8.7/4) is recommended. Alternatively, the “Digital Press Form 1” can be printed with the following settings, and measured with an Eye-one Sis XL, utilizing ColorPort. Save the measurements in the CGATS format, conversion none.

Note: While Fiery Color Profiler Suite recognizes this measurement file format, the line with “DEVCALSTD XRGA” present in certain measurement file headers should be commented out or deleted. This allows the ColorPort measurement file to conform to the CGATS file specification and successfully read by Fiery Color Profiler Suite.

The following print properties are used to capture the printer’s calibrated state for creating an ICC profile. Any other settings should be set to the server’s factory defaults with the exception of media tray settings.

• Media : Media Type : Coated-Glossy

• Media : Media Weight : Paper Weight 4 (105.1 – 163.0 gsm)

• Color : Expert Settings : Color Input : CMYK/Grayscale : Bypass conversion

• Color : Expert Settings : Gray & Black Processing: Gray : CMYK : Off

• Color : Expert Settings : Gray & Black Processing : Black : Black text and graphics : Normal

• Color : Expert Settings : Output : “EFI XF130SM 175Line Edited Goal”

• Image: Halftone Mode : 175 Line + Fine Text (1200 dpi)

Once measurements are made, select “Generic CMYK setting” in Fiery Printer Profiler, and edit the black controls to have black start at 5% and black generation at 90%. Save the new output profile to the server or as a local file to import later. Associate newly created output profile with the previously created calibration set “EFI XF130 175Line” when importing into Command WorkStation. It is important that the edited calibration goal profile is set as default (“EFI FX130SM 175Line Edited Goal”) when you upload the new profile, for this is where the new profile will get it’s calibration goal.

Print the Digital Press Forms

Use the following set of print properties as a baseline for printing the press forms. There are individual exceptions for some of the press forms that will be noted.

• Media : Media Type : Coated-Glossy

• Media : Media Weight : Paper Weight 4 (105.1 – 163.0 gsm)

• Color : Expert Settings : Color Input : CMYK/Grayscale : GRACoL2006 Coated1 (EFI)

• Color : Expert Settings : Color Input : CMYK/Grayscale : Processing method : Full (Output GCR)

• Color : Expert Settings : Color Input : CMYK/Grayscale : Paper simulation : On

• Color : Expert Settings : Gray & Black Processing: Gray : CMYK : Off

• Color : Expert Settings : Gray & Black Processing : Black : Black text and graphics : Normal

• Color : Expert Settings : Output : [newly created output profile]

• Image: Halftone Mode : 175 Line + Fine Text (1200 dpi)

For technical reasons the maximum ink film thickness in offset printing is about 3.5 μm. For coated paper and process colours according to DIN 16 539 the correct colour locations should be achieved with ink film thicknesses between 0.7 and 1.1 μm. 

If unsuitable lithography’s, inappropriate printing stock or unsuitable printing ink are used, however, it may happen that the standardized points at the corners of the CIE chromaticity diagram are not reached. The range of reproducible colors also decreases if the saturation is insufficient. In the illustration the white area shows how the range of colors narrows with the under inking of each of the three process colors. 

In terms of physics the influence of the ink film thickness on the optical appearance can be explained as follows. 

Printing inks do not cover the paper; they are, rather, transparent. The light penetrates the ink. In passing through the ink it encounters pigments which absorb to a greater or lesser extent certain wavelengths.  The higher the pigment concentration and the thickness of the ink film, the more pigments are hit by the incident light and, consequently, the more of it is absorbed. 

Finally, the light rays reach the (white) surface of the printing stock and are reflected. On its way back the light has to pass through the ink film again and only then can it reach the observer’s eye. 

A thick printing ink film absorbs more light and reflects less than a thin one; the observer therefore perceives a darker, more saturated, color hue. The portion of light reaching the eye thus serves as a basis for the assessment of each color.

How many you have wondered why the color you see when printing is different when your customer see in his room?  Have your ever faced an unhappy customer who was upset because the colors were not upto his expectations, whereas when you printed you felt it is more than his expectations?

If you say yes to any one of the above questions, then you are suffering from “Metamerism” issue.

What is Metamerism?

Metamerism is a phenomenon in day to day life of a common man. It occurs, when a color swatch and a sample matching in one light source “differ” in another source of light. A typical example is the problem faced by a common man when a product purchased after matching in showroom light is not matching anymore at home. The object/product match in store under – typically- fluorescent light and they don’t match under incandescent light or day light. The phenomenon is metamerism and the two colors showing the above property are called metameric pair. The fundamental reason for metamerism is that color is a sensation rather than a property of an object. The eyes can register the same sensation from an infinite variety of combinations of different light frequencies. Hence, it is imperative to discuss more about source of light, the object and the observer.
 

So how to Counter it?  A simple light tool for Viewing right Color

The colors of modern digital proofs depend very heavily on the light source used (metamerism). It is therefore important that they are always assessed under a standard light of D50 (5000 K). If a light source with an incorrect color temperature is used, the colors of the proof shift and an assessment is meaningless. With the Ugra light indicator it can be easily deducted whether the light source corresponds to standard light and whether an assessment is valid.

 The Ugra light indicator is used for the visual checking of the color temperature of illuminations for color assessments. For this purpose, the Ugra light indicator is attached to the margin of a proof, where it signals whether the illumination used emits the standard color temperature of 5000 K. If a standard color temperature of 5000 K is used, the patches of the Ugra light indicator appear in the same green color. If the color temperature differs from 5000 K, the patches of the Ugra light indicator show different colors.

 The 9 mm x 75 mm indicator strips have a non-permanent adhesive on the reverse side. This means that they can be attached to the margins of proofs, prints or other objects which have to be viewed under a standard illumination of 5000 K.

The light tool to see things right

Metamerism light indicator

The Ugra metamerism card has a size of DIN A5 and will be used for the control of the illumination. It has the same function as the Ugra light indicator.


For  Print Standardisation project, it is very important to use raw-materials as per the Internationally accepted standard.  You can refer above the CIELAB values for ISO standard Ink.  Before using the ink, you should check with the Ink manufacturer whether the ink supplied to you is in conformance with the above mentioned standards and CIE LAB values.