Photographic printing

From Wikipedia, the free encyclopedia

Photographic printing is the process of producing a final image on paper for viewing, using chemically sensitized paper. The paper is exposed to a photographic negative, a positive transparency (or slide), or a digital image file projected using an enlarger or digital exposure unit such as a LightJet printer. Alternatively, the negative or transparency may be placed atop the paper and directly exposed, creating a contact print. Photographs are more commonly printed on plain paper, for example by a color printer, but this is not considered "photographic printing".

Following exposure, the paper is processed to reveal and make permanent the latent image. Printing on black-and-white paper

The process consists of four major steps, performed in a photographic darkroom or within an automated photo printing machine. These steps are:

Exposure of the image onto the sensitized paper using a contact printer or enlarger;

Processing of the latent image using the following chemical process: o Development of the exposed image reduces the silver halide in the latent image to metallic silver; o Stopping development by neutralising, diluting or removing the developing chemicals; o Fixing the image by dissolving undeveloped silver halide from the light-sensitive emulsion: o Washing thoroughly to remove processing chemicals protects the finished print from fading and deterioration.

Optionally, after fixing, the print is treated with a hypo clearing agent to ensure complete removal of the fixer, which would otherwise compromise the long term stability of the image. Prints can be chemically toned or hand coloured after processing.[ Enlarger

From Wikipedia, the free encyclopedia

An enlarger is a specialized transparency projector used to produce photographic prints from film or glass negatives using the gelatin silver process, or from transparencies. Construction

All enlargers consist of a light source, normally an incandescent light bulb, a condenser or translucent screen to provide even illumination, a holder for the negative or transparency, and a specialised lens for projection. The light passes through a film holder, which holds the exposed and developed photographic negative or transparency.

Prints made with an enlarger are called enlargements. Typically, enlargers are used in a darkroom, an enclosed space from which extraneous light may be excluded; some commercial enlargers have an integral dark box so that they can be used in a light-filled room.

The parts of the enlarger include baseboard, enlarger head, elevation knob, filter holder, negative carrier, glass plate, focus knob, girder scale, timer, bellows, and housing lift.

Enlarger lens: using the diaphragm - aperture ring the photographer adjusts the iris.

The image from the negative or transparency is projected through a lens fitted with an adjustable iris aperture, onto to a flat surface bearing the sensitized photographic paper. By adjusting the ratio of distance from film to lens to the distance from lens to paper, various degrees of enlargement may be obtained, with the physical enlargement ratio limited only by the structure of the enlarger and the size of the paper. As the image size is changed it is also necessary to change the focus of the lens.

An easel is used to hold the paper perfectly flat. Some easels are designed with adjustable overlapping flat steel "blades" to crop the image on the paper to the desired size while keeping an unexposed white border about the image. Paper is sometimes placed directly on the table or enlarger base, and held down flat with metal strips.

The enlargement is made by first focusing the image with the lamp on, the lens at maximum aperture and the easel empty, usually with the aid of a focus finder. The lamp is turned off, or in some cases, shuttered by a light-tight mechanism.

The image is focussed by changing the distance between the lens and the film, achieved by adjusting the length of a light-tight bellows with a geared rack and pinion mechanism

Electronic timer: photographers choose exposure time.

The lens is set to its working aperture. Enlarging lenses have an optimum range of apertures which yield a sharp image from corner to corner, often around f8. The lens is normally set to this aperture and any color filtration dialed in, if making a color print or one on variable-contrast black-and-white paper.

The enlarger's lamp or shutter mechanism is controlled either by an electronic timer, or by the operator - who marks time with a clock, metronome or simply by counting seconds - shuttering or turning off the lamp when the exposure is complete. The exposed paper can be processed immediately or placed in a light-tight container for later processing. Paper processing

After exposure, photographic paper is developed, fixed, washed and dried using the gelatin silver process.

Assignment Directions:

Open both the Chapter 8 Worksheet link and print yourself a new copy to fill out, or you can use the worksheet passed out in class. Read the general overview on the previous page after reading Chapters 8 in your text book, and answer the questions on the worksheet as completely and as best as you can. All answers can be found in the above information as well as the text.

If you have any questions…feel free to email me at [email protected]