1. Light painting resolution: refers to how many points can be emitted in one inch of length; the unit is: PDI Optical density: refers to the number of silver particles restored in the emulsion film, that is, the light blocking ability, the unit is “D”, the formula :D=lg (incident light energy/transmitted light energy) Contrast coefficient: Contrast coefficient refers to the extent to which the optical density of a film changes after being exposed to different intensities of light and processed according to standard processing processes!
2. The structure of light-painted film (silver salt film)
3. The composition and function of light painting film
4. Surface layer: It plays the role of preventing scratches and protecting the silver salt emulsion layer from being damaged!
5. Drug film (silver salt emulsion layer) imaging layer. The main components of the emulsion are silver salt photosensitive substances such as silver bromide, silver chloride, and silver iodide, as well as gelatin and pigments. The silver salt can restore the silver core center under the action of light. However, silver salt is insoluble in water, so gelatin is used to suspend it and is coated on the film base. The pigment in the emulsion plays a sensitizing role.
6. The adhesive layer promotes the adhesion of the emulsion layer to the film base. That is, in order to improve the bonding force between the emulsion and the film base, an aqueous solution of gelatin and chromium vitriol is used as the bonding layer to ensure a firm bond.
7. Polyester base carrier film base, the negative film base generally uses nitrocellulose, acetate cellulose or polyester film base. The first two bases are highly stretchable, and the polyester base is relatively stable in size5. The anti-halo/static layer prevents halo and static electricity. Under normal circumstances, the bottom surface of the photographic film base will reflect light, causing the emulsion layer to re- Sensitivity produces halos. To prevent halos, an aqueous solution of gelatin and alkaline fuchsin is coated on the back of the film base to absorb light. Called the anti-halo layer.
8. Operation process of light painting film
9. Light painting Light painting is actually a light process. After the film is exposed, the silver salt restores the silver center, but at this time the pattern cannot be seen on the film, which is called a latent image. Commonly used light machines include: flat plate type Laser plotter, inner barrel laser plotter, outer drum laser plotter, etc.
10. Development reduces the illuminated silver salt into black silver particles. The temperature of the developer has a great influence on the development speed. The higher the temperature, the faster the development speed. The more suitable development temperature is 18℃～25℃.
11. The main components of shadow fluid are composed of developer, protective agent, accelerator and inhibitor. Its functions are as follows:

(1) Developer: The function of the developer is to reduce the photosensitive silver salt into silver. Therefore, the developer is also a reducing agent. Chemicals commonly used as reducing agents include hydroquinone and parametaminophen sulfate.

(2) Protective agent: The protective agent prevents oxidation of the developer. Sodium sulfite is commonly used as the protective agent. 3. Accelerator: The accelerator is an alkaline substance that accelerates development. The commonly used accelerator is sodium carbonate. Borax, sodium hydroxide, etc., among which sodium hydroxide is a strong accelerator.

(3) For fixing, use ammonium thiosulfate to remove the silver salt that has not been reduced to silver, otherwise this part of the silver salt will be exposed again and destroy the original image. Jialichuang Laser Steel Mesh

(4) Inhibitor: The function of the inhibitor is to inhibit the reduction of the unexposed silver salt to silver, which can prevent the unexposed parts from producing fog during development. Potassium bromide is a very good inhibitor, which has strong photosensitivity The suppression is weak in places where light sensitivity is weak, but the suppression is strong in places where light sensitivity is weak.

5. Process parameters of each process and solutions to common problems
6. Development and development should pay attention to the control of several parameters:

A. Concentration of the solution: The concentration is generally prepared according to the parameters provided by the material supplier. The concentration of the new solution may be higher, while the concentration of the old solution is lower. You need to pay attention to controlling the development time to avoid over-development and under-development!

B. Temperature of the potion: If the temperature is too high, it will cause excessive display and a large halo at the edge of the line.

C. Development time: The control of development time has a direct impact on the effect of photographic film. The development time is short and the optical density is insufficient; the development time is lengthened and the fog is aggravated.

2. Fixing and fixing time must be controlled at more than 60 seconds. When the fixing time is not enough, the background color of the production plate is not transparent enough. When the concentration of the solution decreases, the fixing time should be appropriately lengthened. When the potion is too old, silver powder precipitation will aggravate the fog.
3. Water washing If the washing time is not enough, the production plate will easily turn yellow.
4. Other matters needing attention

A. Do not expose photographic films to safety lights for a long time, as this will aggravate fogging.

B. Photographic films should be kept dry. Humid photographic films will become more foggy.

C. Do not drip the fixing solution into the developing solution.

D. If the washing time is not enough, the production plate will easily turn yellow.

6. Evaluation of light painting negative effects
7. The optical density of the film: It can be detected by an optical density measuring instrument. Generally, the light-blocking area should be greater than 4.0D; the light-transmitting area should be less than 0.15D.
8. Contrast Contrast: You must choose a film with a larger contrast coefficient to produce a working film with better contrast. Otherwise, the optical density will be difficult to achieve. Even if you lengthen the development time and make the optical density meet the requirements, it will still give you It makes the fog worse.
9. The gradient of the line edge means whether the black and white are clear, and whether the line edge is sharp! 4. Whether there are trachoma. Some films can easily produce trachoma if the light intensity is not adjusted well.

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