Photographic paper

Photo paper or photo paper (short for photographic paper ) in the classical sense is a light- sensitive coated material, the backing is usually made of paper, for the production of black and white or colored supervision images on optical- photochemically.

Inkjet printers and laser printers can deliver with the help of special art paper prints photo -like quality. These special papers for photographic purposes are also referred to as photo paper, but not discussed in this article.

• 2.1 color negative paper ( formation of color images from color negatives )
• 2.2 color positive paper ( formation of color images of color slides )

• 3.1 Shiny
• 3.2 Matt
• 3.3 silk screen

Classic photo paper designed for black and white images

Black and white photo paper is produced in various gradations or degrees of hardness, typically there are papers with gradations from 0 ( soft) to 5 ( hard). Variable contrast paper is photo paper with wandelbarem contrast behavior. Depending on the color, is illuminated, a softer or harder gradation can be achieved.

Variable contrast papers are composed of two layers. A layer having a hard gradation is sensitive only to blue light. The second layer has a smoother gradation is only sensitive to green light. By matching the appropriate light shares with a so-called variable contrast filters (either colored plastic films or by setting a specific color of light in Color enlarger ) outweighs either the exposure in the hard-working or those in the soft -working layer. This means that all gradations from 0 to 4 or 0 and 5 can be generated.

Baryta

1866 developed Martinez - Sanchez and J. Laurent in Madrid barytierte paper as a base for photo-sensitive emulsions. The classic photo paper for a black and white image consists of a solid, a cardboard carrier, on a white layer of barium sulfate ( barite also called ) and then a photosensitive layer has been applied. The photosensitive layer, as in the classic photography usual, from slurried in gelatine ( technical term: suspended ) silver halide grains, mainly silver. The photosensitive layer, as in the other photographic materials, also referred to as an emulsion, while it is actually a suspension.

The silver of the photographic paper is sensitive only to blue and violet light, so it can be processed at a red or yellow-green safelight.

After the exposure (ie, the projection of a black and white negative with white light onto the light- sensitive surface of the photographic paper, duration and intensity are precisely control in order to achieve a correct exposure ) in a so-called Enlargement ( looks like and has for example, the function of a beam from top to bottom slide projector ) is the photographic paper developed, fixed, washed and dried. However, the paper images are not particularly true to size, because it passes through the wet processing and subsequent drying, the paper backing warping. For drying, therefore, a press is often used. In conjunction with a reflective foil thus shiny surfaces can be produced. The durability of these images is the highest of all conventional photographic materials, it is 100 years and more.

The main disadvantage of baryta papers is their high processing overhead. The last wet phase, particularly the watering, regularly has to last at least 30 minutes, as in the previous development and Fixage the papierne carrier sucks full of chemicals that need to be removed in the final wash, otherwise the picture is not tenable. When the power of a Sodabades before the final rinse it may however be reduced to 15 to 20 minutes.

Baryte papers are therefore now mostly used only for higher-quality photo - elaborations and lovers purposes. For bulk copies they have lost all meaning, at least in the Western world.

PE papers

With PE - paper of the paper support is on both sides with a layer of the plastic is polyethylene (abbreviated as PE) laminated. The PE coating prevents penetration of chemicals and water in the paper layer, thereby significantly reduce the processing times, in particular at the final rinse. You will need is a few minutes with running water. Drying can be done in the air, for example newsprint in the course of a few hours. Should it go faster, there are devices (PE- dryer) that will do this with hot air in a few minutes.

PE deductions are much more dimensionally stable than baryta prints. A decided disadvantage is the lower shelf: The polyethylene endures an estimated 30 years, after which is expected to chapping and peeling.

Also the picture of silver ( the blackening of a true black and white image consists of finely divided and therefore black -appearing silver ) is less well preserved, the paper layer in Barytabzügen can have harmful substances that act on the image silver and change it or can destroy, to one in PE deductions absorb some degree and so keep away from the image silver.

Classic photo paper for color images ( color papers )

Color papers differ from black and white papers by the type of light-sensitive layer:

To view all colors reproduce as faithfully as possible, ( top to bottom ) one blue-, green - and red-sensitive layer. When processing arise in these layers dyes in the respective complementary color, ie yellow, purple (also called magenta) and cyan (also called cyan ).

Accordingly, the processing considerably more complex: The individual processing steps must be strictly adhered to in terms of duration and processing temperature in order to avoid color casts.

In color photography, PE-coated papers have completely replaced the baryta papers.

Color negative paper ( formation of color images from color negatives )

By far the largest proportion of color images is produced by color negatives. The image quality is generally significantly better than for color images according to slides, as negatives for the subsequent production of color images is particularly adapted ( soft gradation, color masking for compensating for defects of the layer absorption dyes).

Color positive paper ( formation of color images of color slides )

The role of color positive paper is to produce a usable image formats from the high-contrast color slide presentation. This is more difficult than it might first appear. The positive paper has to work very soft to mitigate the high contrasts, because in contrast to the slide ( about 1:1000 ) can be a photo only a considerably lower contrast ratio ( about 1:100 ). In contrast flattening the saturation of colors suffers. Nevertheless, the color image often contains blown-out lights and tapered blacks.

Therefore, in this niche area held the digital technology early collection: the slides are Ever since the early 90s to produce color images by Dias first digitally scanned, the scan finds an automatic contrast correction, then the corrected digital image is exposed on color negative paper.

A notable special case of the color positive paper forms the Ilfochrome Paper ( formerly Cibachrome ). It operates on a different physicochemical methods than any other color films and papers, this method is called silver dye bleach process, while the dyes are bleached during the process, depending on the exposure more or less strong. The dyes used are so-called azo dyes, they are brighter and more light than any other photo dyes.

A disadvantage of the method, the relatively low sensitivity of the material and the high material price of the prints is ( for photo paper plus processing chemicals, equipment not counted ), so it was never used on the mass market.

Surface structure

Because the gelatin layer, which serves as a carrier for the color pigments, a higher refractive index than air, occur on the surface of unwanted reflections of the incident light. There are different ways to deal with these reflections.

The most widespread is the glossy photo paper and is now offered by many service providers photo as the only option when Ausbelichten of photos. The surface is substantially smooth and reflexes are sharp, similar to a film or a glass plate. With glossy photos, the colors are more vibrant and contrast perceived as dull in photos. Objectively, however, this impression is based on an illusion. Under optimal light conditions, such as a lighting from the side frontal view of the image, a matt equivalent of a glossy photo with the eye can not distinguish. Looking at a shiny photo at the sharp reflexes occur with both eyes, the human brain is due to the spatial vision able to filter out these partly because they are in a virtual image plane behind the image. The subjective contrast range again includes the photo including the interfering reflections. Therefore, the image appears as a high contrast, it is actually.

Mate

In matte photo paper, the surface consists of a disordered relief. Thus, the reflection is distributed over a larger angular range. The reflections are diffuse. When the light source is far enough away ( a multiple of the image size) to unfavorable light conditions do not act directly in the visible reflections from, but in a uniform reduction of the contrast and color saturation of the entire image, since white light is added. Mat photos so see also view directions from which brilliant photos already show strong reflections, still good, even though they no longer have their full radiance. Under optimal light conditions are matte and glossy photos equivalent.

Silk screen

Is also used so-called Silk or silk screen photo paper with a hexagonally ordered surface structure. It also produces diffuse reflections and to protect the photo against copying. The price of the copy protection is that the coarse structure is clearly visible to the eye.