Correct understanding and use of density meters
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The success of a printing house often depends on its speed and flexibility. Due to the different products and different service targets, the number of prints is getting smaller and fewer, and the variety of jobs is increasing. The medium-format press relies on the advantages of cost and price, both to be set quickly and to achieve stable production conditions. Automated print preparation and easy-to-control paper transfer are the main features of the medium format press.
The medium format press is a press with a paper width of 66-75 cm. It is mainly 74 in Europe and 66, 72, 75 in Japan. A summary of the information on the medium format presses at the recent drupa 2004 exhibition.
Heidelberg 74 series
The 74 series has SM CD 74, SM74, and PM74, which are high-end and mid-range mid-range models.
The Speedmagter CD 74 is rugged and durable for a long time at the highest speeds, thanks to a wide range of paper, cardboard and plastic substrates. It is suitable for companies that need to produce industrial packaging printing in multiple shifts. Digital Prinect CP2000 Press Control Center supports rapid replacement of paper format
And the operation of the substrate.
The Speedmaster CD 74 is available in two formats: C-format 53 cm X74 cm and F-format 60. 5 cm X 74 cm. The models in this series are very flexible. Its features include:
·Automatically perform pre-setting of the paper feeder according to the replacement of the paper web and printing materials, shortening the time for printing preparation.
· The inking unit responds quickly with the Color Fast Solution software.
·Alcolor continuous film-forming dampening device to achieve a stable ink-and-wash balance.
· AirTransfer paper transfer unit with Venturi's patented technology to ensure optimal paper transfer between printing units.
·The developed cleaning device is fully environmentally friendly.
· Heidelberg InkLine direct inking system can automatically fill the ink fountain and monitor the ink volume of the ink fountain.
·Prinect Auto Register enables fully automatic on-board registration control, reducing printing time.
· It can remotely control the axial, circumferential and lateral registration of the coating unit, saving time and reducing waste during start-up.
· DryStar drying system with infrared, hot air and cold air modules to adjust the paper feed to the optimum.
· Pre-setting of the delivery mechanism ensures that the delivery is neat. The paper brake function allows the brakes to be adjusted remotely.
· Fully automatic adjustable paper progeny flipping device.
At present, there are many types and models of density meters manufactured abroad. Generally speaking, the first English letter of the density meter model indicates the first letter of the English word of the nature of the density meter. For example: T for transmission and R for reflection. (M) stands for density meter, O stands for dot area tester, TR stands for transmission and reflection, OT stands for dot area transmission density meter, TD stands for transmission density meter, and RD stands for reflection density meter. The Arabic number following the densitometer model is the product serial number of the densitometer.
Domestically produced models have two supplements, CMF, which represents a color reflection densitometer, and the other, CMT, which represents a transmission densitometer.
1. Measurement of reflection densitometer
A calibrated densitometer must be used to measure the reflection density. All reflection density values, dot gain/TVI in SNAP are based on equipment in ISO T state, and they are ANSI/ISO 5/3 and 5/4 compliant. When printing on newsprint or other rough paper, the SNAP recommended aperture is 4mm.
In all cases, the size of the aperture should be determined in conjunction with the measurement. All measuring instruments are non-polarized. The density side amount is absolute, including paper density. The dot gain/TVI value should be calculated in accordance with ANSI/CGATS.4 (based on the Murray-Davies equation). The measurement of the overprint ratio should also be in accordance with ANSI/CGATS.4 (based on the Preucil overprint equation).
2. Measurement of transmission densitometer
Although the light and positive color panchromatic light values are to be displayed in the transmission densitometer measurement, the transmission densitometer measurement is based on the latter. The correction of the percentage dot area uses a UGRA scale in which 0.5% of the light-colored area is used as the zero-point reference color mark (base fog). The recommended aperture size is 3mm. In any case, the size of the aperture should be determined in conjunction with the actual measurement. The test must meet the requirements of CGATS.9
Standard density meter composition
The densitometer has three basic components (and of course the samples to be measured). These three components include:
1. Lighting system
It consists of a luminaire, an illumination light path, and a power source for illuminating the luminaire. The light emitted by the luminaire is converted to ANSI/ISO standards to provide light of a certain color quality (for example, to balance red, green, and blue light), called source A. This color quality is very close to the quality of the light emitted by a tungsten filament lamp that has never been colored (the densitometer bulb is made of a light that can control the brightness well or provide a pulse to the luminaire to make each flash of light A consistent circuit can be used to supply power. However, regardless of the light and power supply, the luminaire and power supply are guaranteed to be known illumination as part of the incident light in this ratio.
2. System for collecting light and measurement
This system consists of a light receiver, an optical path for collecting light, and a spectroscopic filter that transmits only part of the light in the visible spectrum to the light receiver and blocks other portions of the light. This system of collecting light typically includes a color filter that matches the overall spectral sensitivity to some of the mentioned standards. The previously used color filter set for densitometers used in printing and publishing is roughly equivalent to the color separation characteristics in the printing process. These spectral values have been redefined by the ANSI IT2 committee to produce a documented standard called the T state. This engineering specification allows the densitometers produced by the same manufacturer to be matched, as well as the densitometers produced by different densitometer manufacturers. The density specification for state T is the result of design, side volume, and calibration as defined by the standard response.
3. Signal Processing System
The signal processing system obtains an electrical signal representative of the incident light and the received light energy for calculation and display. This system may be a simple ratio detector that connects to the logarithmic calculation circuit of an analog or digital display. It can also include a memory function that handles functions such as dot gain and contrast.
Is there any way to exclude paper density when measuring with a densitometer? Setting the paper to zero now does not mean that the user does not have to subtract the density of the paper from the reading. We want to subtract the density of the paper from the density of the solid and the density of the screened tones. For the purpose of better communication, be sure to follow this practice. Another print attribute that detracts from the paper density is the density of a quarter of the hue. The density of the quartertone minus the density of the paper (the relative density of the quarter-tone region) better illustrates the effect of the printing ink, or the hue itself, since the density obtained by the side is mostly from the paper. However, if the side amount is absolute and the paper density is included, the in-situ ink density measurement and important printing attributes (such as print contrast, color cast, and gray balance) are better correlated with the human-perceived print image. In summary, if the purpose of using a densitometer is to provide an objective measurement that is well correlated with what the press operator actually sees, the measurement should be absolute, including the density of the paper. It is also very useful to use a modern density meter to measure the quality of unprinted paper (such as relative color and brightness) using three color filters. After the densitometer is equipped with the normalized data of the printing process, We can perform comprehensive and data-managed quality control of the plate making process and printing process.