One, the term
Light painting resolution: refers to how many points one inch length can discharge; Unit is: the PDI
Optical density: refers to the reduction of silver particles in emulsion membrane, namely the light blocking ability, the unit is "D", formula: D = lg (incident light energy/transmission light energy)
Contrast coefficient, contrast coefficient refers to the negative in the different strength of the light? , according to the standard wash process, the degree of its optical density change size!
Second, the structure of light painting film (silver halide film)
3. Light painting film composition and function
1, the surface:
To prevent from scratching role, protect silver halide emulsion layer was not destroyed!
Silver halide emulsion layer 2, ()
Image layer, emulsion ingredient is silver bromide, silver chloride, silver iodide, and silver halide photographic material such as gelatin and pigment in silver halide can restore the silver light under the action of nuclear center. But silver halide does not dissolve in water, so using gelatin into a state of suspension, and coating on the film base, pigment in emulsion is intensifying role.
3, the adhesive layer
Promote the emulsion layer attached on the film base. Namely, to improve the bonding force between emulsion and film base, using the aqueous solution of gelatin, chrome alum as combining layer, make it solid combination.
4, polyester base
Carrier film base, bottom base generally use blades of nitrocellulose, cellulose acetate or polyester film base. The first two film base scale is big, the size of the polyester film base is stable
5, halo/electrostatic prevention layer
Halo and electrostatic prevention, in general, the bottom of the camera acrossed the underside will reflect light, make the emulsion layer of light-sensitive flare again. Use to prevent to produce the halo, gelatin and fuchsine aqueous coating on the back of the film base, used to absorb light. Called anti halation layer.
Four, the operation of the light painting film process
1, light painting,
Light painting is actually a? Silver halide reduction process, light, the film after exposure, the silver, but can't see the graphics on the film at this moment, is called the latent image. Commonly used? Light machine are: plate type laser light painting machine, drum type laser light painting machine, outer barrel type laser light painting machine, etc.
2, the development
The light silver halide back into the black silver grain, the temperature of the developer's influence on the development speed is very large, the higher the temperature, the faster development speed. More suitable for developing temperature of 18 ℃ to 25 ℃. The main components of the liquid film is by the developer, protective agent, accelerating agent and the inhibitor of. Its action is as follows:
3, fixing
Using sulfuric acid and ammonia removal without reduction of silver silver halide, otherwise this part will be exposed, silver halide destruction of the original image.
Is the role of 1, developer: developer light-sensitive silver halide back into silver, as a result, the developer is also a reducing agent, commonly used as reductant chemicals have hydroquinone and methyl phenol ammonia sulphate, etc.
2, the protective agent: the role of protective prevent the oxidation of the developer, commonly used sodium sulfite do protective agent.
3, accelerating agent, accelerating agent is a kind of alkaline substances, role is to make development faster, commonly used for accelerator with sodium carbonate, sodium borate, sodium hydroxide, etc., the sodium hydroxide is strongly accelerated agent.
4, inhibitors, the role of the inhibitor is no? Silver halide reduction of silver light, can prevent not? Generated when the part in the development of light fog. KBR is as good as inhibitor, weak it strong to the substrate inhibition, strong inhibition and weak to the substrate.
Five, the processing parameters of each process and common problems to solve
1, the development
Should be paid attention to developing several parameters of control:
A, the concentration of the liquid medicine: concentration parameters are generally according to the material suppliers. New solution concentration could be on the high side, and old solution concentration is low, need to pay attention to control the developing time, avoid explicit and underdevelopment.
B, the temperature of the liquid medicine: temperature is too high, cause in this line edge glow.
C, developing time, development time of control has direct influence to the effect of the photographic plate. Developing time
Short, optical density is not enough; Developing time longer, fog is aggravating.
2, fixing
Fixing time must be controlled in more than 60 seconds. Fixing didn't have enough time, the production of blank the base of color is not transparent, when potions concentration lower, should be appropriately extended fixing time. When the liquid is too old, can accentuate silver precipitation fog
3, washed
Such as water washing time is not enough, production blank easy to turn yellow.
4, other considerations
A, photographic plate lights don't long time exposure to the security, the fog will be aggravated.
B, photographic plate should keep dry, wet photographic plate fog.
C, fixing, liquid medicine not to drip into the enhancement in the potions.
D, such as water washing didn't have enough time, the production of blank is easy to turn yellow.
Six, light painted film effect evaluation
1, the optical density of film:
By optical density measuring instrument to detect, general light blocking area is greater than 4.0 D; Photic zone is smaller than 0.15 D.
2, contrast contrast
Choose contrast coefficient larger negatives, work well to make a contrast the negatives, or optical density is difficult to achieve, even if you lengthen the period of development, make the optical density is achieved, but also bring you a fog.
3, line edge gradient
Whether that is to say, black and white. The line edge is sharp!
4, with or without sand holes
Some negative if light section stress is bad, it is easy to produce sand holes.
