PMT 120 PRE-PRESS SECTION

Name : mohd nur azwan bin mohd nazeriNo. Matrix : 2013722793

Lecturer : IRWAN ZAKARIA

IMAGESETTER

An imagesetter is an ultra-high resolution large-format computer output device. It exposes rolls or sheets of either photographic film or bromide paper to a laser light source. Once the film or paper is developed, a very high quality black and white image is revealed. Development (processing) usually occurs in a unit separate to the imagesetter, as does raster image processing.

Imagesetter setter output ranges in width, usually 12 to 44 inches (300 to 1,120 mm). The resolution of an imagesetter is typically between 1200 and 4800 dpi.

The imagesetter has been largely superseded by the platesetter.

Imagesetter film is a silver halide-coated plastic film very similar to normal black & white photographic film, except the spectral sensitivity is reduced to a much narrower band around the output of the laser

of the individual imagesetter. This allows the film to be handled under a (usually red) safelight, instead of in total darkness like most photographic film.

A machine that generates output for the printing process, using either a film-based paper that is photographed or the actual film for making the printing plates. Input to the machine is typically in PDF or PostScript format, and a laser generates the page image directly on the film. Today, in lieu of sending work to a commercial print house, laser printers are widely used to create finished output. However, the 2,540 dpi resolution of the imagesetter produces very high-quality photographs and halftones. See CTP, PDF and PostScript.

A Brief History of Setting Type Typesetting dates back to Gutenberg in the 1400s, where lead letters were set by hand and pressed against paper and ink. From the late 1800s into the 1960s, operators of Linotype and other comparable machines keyboarded lines of text that were cast from hot metal into slugs for printing. The metal was reused for the next run. In the 1960s, the "phototypesetter" created film negatives that were used to make offset printing plates. It passed light through a spinning photomask to obtain the font style and then through lenses to create the point size. Subsequently, film was exposed to images on a CRT.

CHEMICAL

1) DEVELOPER

In the processing of photographic films, plates or papers, the Photographic Developer (or just developer) is one or more chemicals that convert the latent image to a visible image. Developing agents achieve this conversion by reducing the silver halides, which are pale-colored, into silver metal, which is black (when a fine particle).[1] The conversion occurs within the gelatine matrix. The special feature of photography is that the developer only acts on those particles of silver halides that have been exposed to light. Generally, the longer a developer is allowed to work, the darker the image.

Chemical composition of developersFor black-and-white photography, the developer typically consists of a mixture of chemical compounds prepared as an aqueous solution. Three main components of this mixture are:[2]

developers. Popular developers are metol (monomethyl-p-aminophenol hemisulfate), phenidone (1-phenyl-3-pyrazolidinone), dimezone (4,4-dimethyl-1-phenylpyrazolidin-3-one), and hydroquinone (benzene-1,4-diol).

Alkaline agent such as sodium carbonate, borax, or sodium hydroxide to create the appropriately high pH

sodium sulfite to delay oxidation of the developing agents by atmospheric oxygen.

Hydroquinone is superadditive with metol, meaning that it acts to "recharge" the metol after it has been oxidised in the process of reducing silver in the emulsion. Sulfite in a developer not only acts to prevent aerial oxidation of the developing agents in solution, it also facilitates the regeneration of metol by hydroquinone (reducing compensation and adjacency effects) and in high enough concentrations acts as a silver halide solvent. The original lithographic developer contained formaldehyde (often added as paraformaldehyde powder) in a low sulfite/bisulfite solution.

Most developers also contain small amounts of potassium bromide to modify and restrain the action of the developer[3] to suppress chemical fogging. Developers for high contrast work have higher concentrations of hydroquinone and lower concentrations of metol and tend to use strong alkalis such as sodium hydroxide to push the pH up to around pH 11 to 12.

Metol is difficult to dissolve in solutions of high salt content and instructions for mixing developer formulae therefore almost always list metol first. It is important to dissolve chemicals in the order in which they are listed. Some photographers add a pinch of sodium sulfite before dissolving the metol to prevent oxidation, but large amounts of sulfite in solution will make it very slow for metol to dissolve.

Because metol is relatively toxic and can cause skin sensitisation, modern commercial developers often use phenidone or dimezone S (4-hydroxymethyl-4-methyl-1-phenyl-3-pyrazolidone) instead. Hydroquinone can also be toxic to the human operator as well as environment; some modern developers replace it with ascorbic acid, or vitamin C. This, however, suffers from poor stability. Ascorbate developers may have the advantage of being compensating and sharpness-enhancing, as oxidation by-products formed during development are acidic, meaning they retard development in and adjacent to areas of high activity. This also explains why ascorbate developers have poor keeping properties, as oxidised ascorbate is both ineffective as a developing agent and lowers the pH of the solution, making the remaining developing agents less active. Recently, claims for practical methods to improve the stability of ascorbate developers have been made by several experimenters.[citation needed]

Other developing agents in use are p-aminophenol, glycin (N-(4-hydroxyphenyl)glycine), pyrogallol, and catechol. When used in low sulfite developer composition, the latter two

compounds cause gelatin to harden and stain in the vicinity of developing grains. Generally, the optical density of the stain increases in the heavily exposed (and heavily developed) area. This is a property that is highly sought after by some photographers because it increases negative contrast in relation to density, meaning that highlight detail can be captured without "blocking" (reaching high enough density that detail and tonality are severely compromised). Hydroquinone shares this property. However, the staining effect only appears in solutions with very little sulfite, and most hydroquinone developers contain substantial quantities of sulfite.[citation needed]

In the early days of photography, a wide range of developing agents were used, including chlorohydroquinone, ferrous oxalate,[4] hydroxylamine, ferrous lactate, ferrous citrate, Eikonogen, atchecin, antipyrin, acetanilid and Amidol (which unusually required mildly acidic conditions).

Developers also contain water softening agent to prevent calcium scum formation (e.g., EDTA salts, sodium tripolyphosphate, NTA salts, etc.).

The original lithographic developer was based upon a low sulfite/bisulfite developer with formaldehyde(added as the powder paraformaldehyde). The very low sulfite, high hydroquinone and high alkalinity encouraged "infectious development"(exposed developing silver halide crystals collided with unexposed silver halide crystals, causing them to also reduce) which enhanced the edge effect in line images. These high energy developers had a short tray life, but when used within their tray life provided consistent usable results.

Modern lithographic developers contain hydrazine compounds, tetrazolium compounds and other amine contrast boosters to increase contrast without relying on the classic hydroquinone-only lithographic developer formulation. The modern formulae are very similar to rapid access developers (except for those additives) and therefore they enjoy long tray life. However, classic lithographic developers using hydroquinone alone suffers very poor tray life and inconsistent results.

2) FIXER

Photographic fixer is a mix of chemicals used in the final step in the photographic processing of film or paper. The fixer stabilises the image, removing the unexposed silver halide remaining on the photographic film or photographic paper, leaving behind the reduced metallic silver that forms the image. By fixation, the film or paper is insensitive to further action by light. Without fixing, the remaining SILVER HALIDE would darken and cause fogging of the image. Fixation is commonly achieved by treating the film or paper with a solution of thiosulfate salt. Popular salts are sodium thiosulfate—commonly called hypo—and ammonium thiosulfate—commonly used in modern rapid fixer formulae.[1] Fixation involves these chemical reactions (X = halide, typically Br-):[2]

AgX + 2 S2O32- → [Ag(S2O3)2]3- + X-

AgX + 3 S2O32- → [Ag(S2O3)3]5- + X-

Fixer is used for processing all commonly used films, including black-and-white films, Kodachrome, and chromogenic films. In chromogenic films, the remaining silver must be removed by a chemical mixture called a bleach FIX, sometimes shortened to blix. This mixture contains ammonium thiosulphate and ferrous EDTA, a powerful chelating agent.

After fixation, washing is important to remove the exhausted chemicals from the emulsion. Otherwise they cause image deterioration. Other treatments of the remaining silver-based image are sometimes used to prevent "burning".

Hypo was apparently first used in PHOTOGRAPHY by the Rev. Joseph Bancroft Reade in 1837.[3]

3) WATER

Water use to washing. In photography and printing, washing is an important part of all film processing and printmaking processes. After materials have been fixed, washing removes unwanted and exhausted processing chemicals which, if left in situ, may cause deterioration and destruction of the image.[1]

A disadvantage of the use of thiosulfate as a fixer is its ability to dissolve elemental silver at a very slow rate. If films or papers are inadequately washed after fixing, any residual fixer can slowly bleach or stain the photographic image. For prints on high grade fibre papers, a period of continuous washing in clean, cold water for up to 40 minutes may be required. For modern plastic (resin) coated papers, washing for as little as 2 minutes in warm water can be sufficient to eliminate residual fixer. Washing aids (also called hypo clearing agents) can be used to make the process of removing fixer faster and MORE thorough.

A quick, water-saving, and archival technique for washing film fixed with nonhardening fixer in a spiral tank is the popular "Ilford method":[2]

Fill the developing tank with tap water at the same temperature as the fixer (+/-5 °C or 9°F)—maintaining a CONSTANT bath temperature during processing is necessary to avoid reticulation of the emulsion;

Invert the tank five times and drain it completely; Fill the tank again, invert it ten times, and drain it completely; Fill the tank again, invert it twenty times, and drain it completely. The film is now washed.

More conventional darkroom practice recommends washing film for 30 minutes or longer, with a flow of water sufficient to change the water in the washing container at least three times. This is not needed when non-hardening fixers are used.

Over-washing can actually reduce the archival properties of film, as thiosulfate in very small concentrations has been shown to have a beneficial effect on film image stability.[3]

FILM1) NEGATIVE FILMIn photography, a negative is an image, usually on a strip or sheet of transparent plastic FILM, in which the lightest areas of the photographed subject appear darkest and the darkest areas appear lightest. This reversed order occurs because of the extremely light-sensitive chemicals a camera film must use to capture an image quickly enough for ordinary picture-taking, which are darkened, rather than bleached, by EXPOSURE to light and subsequent photographic processing.

In the case of color negatives, the colors are also reversed into their respective complementary colors. Typical color negatives have an overall dull orange tint due to an automatic color-masking feature that ultimately results in improved color reproduction.

Negatives are normally used to make positive prints on photographic paper by projecting the negative onto the paper with a photographic enlarger or making a contact print. The paper is also darkened in proportion to its exposure to light, so a second reversal results which restores light and dark to their correct order.

Negatives were once commonly made on a thin sheet of glass rather than a plastic film, and some of the earliest negatives were made on paper.

It is incorrect to call a photograph a negative solely because it is on a transparent material. Transparent prints can be made by printing a negative onto special positive film, as is done to make traditional motion picture film prints for use in theaters. Some films used in cameras are designed to be developed by reversal processing, which produces the final positive, instead of a negative, on the original film. Positives on film or glass are known as transparencies or diapositives, and if mounted in small frames designed for use in a slide projector or magnifying viewer they are commonly called slides.

2) POSITIVE FILMA positive is a film or paper record of a scene that represents the color and luminance of objects in that scene with the same colors and luminances (as near as the medium will allow). Color transparencies are an example of positive photography: the range of colors presented in the medium is limited by the tonal range of the original image (dark and light areas correspond). It is opposed to a negative where colors and luminances are reversed: this is due to the chemical or electrical processes involved in recording the scene. Positives can be turned into negatives by appropriate chemical or electronic processes. Often, with the use of digital imaging, computers can automatically complete this process.