The hottest screen printing base plate photographi

2022-10-19
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Screen printing plate photographic plate making process (VI)

because some parts of the original are too dark, the dots on the photosensitive film are not easy to form full black. In order to form delicate dots locally, flash exposure is required, as shown in the figure. The picture shows that the film and contact screen are adsorbed on the vacuum plate. At the turn of closing the cassette, the film is added at right angles to the cassette, and the light with yellow filter is used for flash exposure. The flash exposure time is selected according to the standard density hierarchy

after the flash exposure, close the cassette, adjust the aperture to 16 ~ 22F, and carry out the main exposure at the selected time. Generally, this can show all levels. If the highlight part of the original is insufficient, you can carry out the highlight exposure again, close the aperture to about 12F, and remove the contact screen for a very short exposure

this kind of exposure must be carried out in two to three stages. Although it is troublesome, you can freely control the tone of the original

The development of

eye negative film is slightly different from that of line film. During the development of line film, the domestic machinery price should be normalized constantly. Shake the developing disc, but if you constantly shake the developing disc during the development of eye negative film, it will become hard tone, and if you only shake strongly or develop statically when you first put it into the developing disc, it will become soft tone. Therefore, adjusting the shaking and static time can control the tone of the eye negative. The development time must be in accordance with the regulations of the film manufacturer. According to the situation of the original, you can control the step by making half moving and half stationary, or making one quarter moving and three quarters stationary. Or, during the development process, it is decided whether to shake or rest according to the situation of checking the negative version at that time

as for the time of stopping display, fixing and washing, the time is the same as that of line film

for the finished eye negative film, carefully check the shape and all tones of its points with a magnifying glass. Sometimes uneven blackness can be found on the periphery, which is related to the defects of the film itself, poor contact screen sealing, overexposure, overexploitation, etc. light cases can be treated with hematite tasol

The quality of the negative film with

eyes is closely related to the final printing effect, so the printing effect should be often put in mind when checking its tone

After the negative film of

mesh is completed, it must be made into positive film in order to make plate, and the method is the same as that of line plate making. However, coarse contact screens such as 30 line and 40 line used in silk printing cannot be bought in the market, so 130 line or 150 line screens can be used to make fine screen plus negative films with good gradation, and then enlarge them three to five times to make positive films

after making a positive film, check again whether the step is appropriate. Silk screen prints are often harder than the tone of the original. The high-profile part should be maintained at about 20%; The points of the dark part should be controlled at about 60 ~ 70%. But these depend on the printing conditions and cannot be generalized

the point can be smaller after thinning and correction. If it is corrected with a positive film, it will be sent to the Western powers at that time to break the closure of the Qing government with a strong ship and a sharp gun. If it is corrected with a negative film, it will be dimmed. If the mixture of red blood salt and baking soda is used, the point can only be smaller and cannot be restored. Therefore, the simplest way is to wash with running water while applying a thin layer of liquid with a brush to make it work little by little and repeatedly, in order to achieve the desired brightness

the following is a brief introduction to the process of indirect addition photography and direct addition Photography:

a. indirect addition. Indirect addition is to take continuous negative adjustment pictures first, and then make positive point negatives through the screen after a certain amount of trimming

a. there are some advanced tension machines on the market, in addition to the above items, the production of continuous negative adjustment pictures. When shooting continuous negative adjustment pictures, on the one hand, we should consider the contrast of the original, on the other hand, we should consider the tolerance of the screen used for positive image overtime. We should not only make the original tone level reappear on the photosensitive film, but also ensure that the density range of the negative picture is within the screen tolerance. The former is mainly solved by masking, while the latter is solved by controlling exposure time and development on the basis of masking. The density range of negative pictures is generally controlled between 0.3 and 1.6. After shooting, you can make up and trim appropriately according to the requirements of plate making. If the contrast of the negative version still needs to be adjusted, you can use the mask after taking photos, that is, copy a short mask with reduced contrast through the negative image, and then make an additive version after it is combined with the negative version

b. making of positive plate. The screen used for indirect addition is mainly magenta screen, with a tolerance of about 1.6. The dots on the positive plate must have sufficient density to meet the requirements of silk screen printing, and the tone contrast of the positive plate must meet the requirements of the original and silk screen printing. In practice, it is often difficult to meet the above requirements with only one exposure, especially the density of small dots is not enough, and the increase of exposure and tone will be lost. Therefore, multiple exposures are often used for additional exposure. The specific methods are as follows:

main exposure: exposure is carried out based on the appropriate middle tone to fix the main level of the pattern

flash exposure: remove the negative version, and only expose the photosensitive film comprehensively, evenly and briefly through the screen, so that the high-profile dots meet the requirements. It should be noted that there should be no displacement between the screen and the photosensitive film, which is generally guaranteed by the nail hanging method

no exposure: if the above two exposures have met the requirements, no exposure can be carried out. But sometimes the dark tone level is not enough and needs further adjustment. This kind of exposure can be used. The specific method is to remove the screen and expose it briefly through the negative picture. The relative position of the negative picture and the photosensitive film should be consistent with that of the main exposure

no exposure and flash exposure are also called auxiliary exposure. In operation, the negative picture, mask, screen and photosensitive film all need to be punched and positioned without relative displacement. Auxiliary exposure should be strictly controlled. In general, the flash exposure range should be about 3% of the main exposure, and the non exposure range should be 1 ~ 2% of the main exposure

in addition, if magenta contact screen is used for positive picture, the tone of positive plate can be adjusted by changing the color temperature of exposure light source. The principle is that the magenta screen has different absorption effects on light of different wavelengths, and the photoreceptor used is a positive color photoreceptor, which has a certain color sensing range, has different sensitivity to light of different wavelengths, and the absorption effect of light on the point on the screen and the blank part is also different, so the tone change of positive pictures such as the number of times, orientation, case and case pattern of each wordid display with different color light is also different. If you use yellow and green light, you can make the positive plate become flat, and blue light can make the positive plate become more sharp. In operation, the color temperature of the light source is generally changed with a color filter. The darker the color of the filter, the greater the degree of change

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