Screen Printing Photographic Plate Making Equipment (4)

3. Camera light source.

The ideal light source for photography is sunlight. Platemaking is done indoors, so the spectrum and color of the selected light source must be close to that of sunlight.

1 The spectrum of the light source. Light source light, the intensity of light at different wavelengths is different. If the wavelength is the abscissa and the relative energy of each wavelength is the ordinate, the distribution curve of the radiant energy of the light source according to the wavelength can be plotted. See Figure 2-95.

The light source spectrum is a very important characteristic of various characteristics of the light source. Photographic plate light source wavelength range should be 400 ~ 700nm, its spectrum should be close to the continuous spectrum of sunlight.

2 The color of the light source. The color of the light source has two meanings. One is the total color sensation seen when the human eye directly observes the light source. This is called the color table of the light source, and is represented by the color temperature; the other is the light source irradiating on the object. The objective effect produced is expressed by the color transfer coefficient.

The color temperature of the light source is generally based on the absolute black body temperature radiation effect, that is, the color of the absolute black body heated to a certain temperature is basically the same as the color of the light source, and the absolute temperature of the absolute black body is the color temperature of the light source. Absolute temperature is equal to Celsius plus 273 degrees Celsius. That is 0°C+273K,

(T)K=t(°C)+273

The quality of light transmission is based on the color transfer coefficient as a quantitative standard. The coefficient of transmission of sunlight is set at 100. The color of the object displayed under illumination of a certain light source and in sunlight, such as the color closer to the sun, the closer the color transfer coefficient is to 100, and vice versa to less than 100.

3 luminous flux, luminous efficiency. Luminous flux is the total amount of visible light emitted by the light source in each second, expressed in lumens (lm). The number of lumens emitted for each watt of power consumed by a light source is called the number of light sources.

The optical properties of the plate-making camera light source are listed in Table 2-31.

Table 2-31 Optical characteristics of plate camera light source

Light source type Power (W) Luminous flux (lm) Luminance nt Luminous efficiency (lm/W) Color temperature (K) Average color-transfer coefficient life (hours) Use Sun - 1.6 x 109 5900 100
Incandescent tungsten lamp vacuum 15 100 4×106 2.9 2400 99 1000 Darkroom safety light inflation 300 4100 15×106 10～20 2850 99 1000 Dry film copy halogen tungsten bromine tungsten 100 20～32 3400 99 50 Electronic light source Iodine tungsten 1000 21000 5×107 27 3200 (high)
2800 (center) 99 50 (high)
1500 (in) Luodeng copy infrared lamp 500 - 18 to 20 2500K or less - 2000 fluorescent fluorescent lamp 40 2560 7 × 103 50 ~ 70 5000 3000 Ancient painting color separation, general illumination plate fluorescent lamp 800 40 3200 ~ 6000 300 ~ 500 direct-attached separation black light 40 - - 40 - - 2000 printing plate (photosensitive resin plate)
Carbon lamp exchange 30 ~ 40V
40～50A 3.5×104 1.5×108 40～50 5500 Wet film camera DC 30～40V
40 to 50A 3.68×104 1.8×108 40 to 50 5500
Metal Halide Deuterium Lamp 1000 7~8×104 80 6000 85 200 Photograph, Roden's Copy Neon Lamp Long Arc 3000 6~7×104 1.6×108 35～50 5700～6000 94 1000 Color Separation Printing Short arc 3000 7×104 5.5×108 30～50 6000 94 500 Straight color separation (point light source)
Pulse (tubular) 8000 32×104 1010 40 6000 95 250 Direct-mount color separation strobe (tubular) 8000 1010 5600 95 Direct color separation

4 photo (copy and copying) light source, should meet the following basic requirements:

High luminous intensity, uniform illuminance, less heat radiation, energy saving, less affected by ambient temperature, humidity, and airflow; emission spectrum should include all areas of the visible spectrum; spectral power distribution of the light source should be adapted to the spectral absorption range of the plate-making photosensitive material; high color temperature , Photometric stability; simple structure, easy operation, low cost, no pollution to the environment, not harmful to the human body.

The commonly used plate-making light sources include fluorescent lamps, charcoal lamps, Xenon lamps, Xenon lamps, and halogen lamps.

a. Fluorescent lamp. Also known as a fluorescent lamp, the luminous intensity is stable, and the spectrum is close to daylight. It is mainly used for photo separation.

b. Charcoal lamp. Also known as an arc lamp, it emits a strong light from an arc generated by a carbon electrode. The spectrum is a continuous spectrum with the highest luminous energy in the violet and ultraviolet portions, a color temperature of 4000-5000 Ã…, and a luminous efficiency of 40-50 lm/W (lumen/watt).

Carbon lamps are easy to operate and inexpensive, but their luminosity is not stable enough to produce smoke. The strong UV rays emitted from it can damage the eyes and cannot be viewed directly during operation, and should be worn with protective glasses.

Carbon lamp is suitable for screen version light source.

c. Lights. The xenon lamp emits light using xenon gas sealed in a quartz tube. Its color temperature is 6000, luminous efficiency is 30 ~ 50lm/W. The advantages are: the light tube is small in size, the spectrum is close to the solar spectrum, smokeless and ashless. The disadvantage is that the heat generation is large and an air-cooled or water-cooled device is required.

The Xenon lamp is suitable for answering camera light sources.

d. Halogen lamps. Halogen lamps are tungsten regenerative light sources developed on the basis of incandescent lamps (tungsten lamps). Its color temperature is about 3200, luminous efficiency is generally 20 ~ 30lm/W, and the emission spectrum is continuous spectrum. The advantages are: the ignition starting device is simple, the illuminance is uniform, the brightness and the color temperature can be adjusted by changing the voltage during operation, and the price is lower. The disadvantages are: low luminous efficiency, large heat, and lack of ultraviolet light.

Halogen lamps are mainly used for photo separation. It is not suitable for plate making of dichromic acid photosensitive materials.

e. The xenon lamp is a gas discharge light source with a spectrum close to sunlight, a color temperature of 5000-6000 Ã…, and a luminous efficiency of 80-90 lm/W. The advantages are: high luminous intensity, stable light, and no pollution. The disadvantages are: long starting time, more ultraviolet rays, and necessary protective measures during operation.

The Xenon lamp is used for photo-separation and rich darkness; it is used for direct screen color separation, neatly shaped and smooth.