Invertible film

A invertible film (also called very usually slide , slide , ekta , or even scala if it is a black and white process) is a photographic type of film which records the Lumière in its emulsion directly into positive, i.e. without inversion of the values (contrary to a negative Film).

The resulting image can be thus observed directly, either on a luminous table, or by projection. There exist processes color like black and white.

Characteristics & interest

The base of film being transparent and without coloured mask, the resulting image can be observed directly either on a luminous table, or by projection. It is this direct side which many photographers like - indeed, the image does not need to be reinterpreted in laboratory to find the colors of origin (as with negative films color).

An invertible film color can be as drawn on paper, as it is via the use of internégatif or processes such as the Ilfochrome (color) or the digitalization followed by the pulling of the file.

One can assemble each individual image within a framework (out of plastic or paperboard) of 5x5 cm facilitating the projection - one speaks then about Diapositive. This format also is very adapted to the photojournalists and the agencies, which made a basic tool of it:

  • One can register easily within the framework of the data concerning the catch of sight (date, place and/or subject).
  • One can individually classify the best images by topic or subject.
  • Each image is ready with the use and does not require additional treatment of laboratory.

With the arrival of numerical (to digitize and manage the files initially, for directly taking the photographs in a second) invertible films color lost of their professional attraction.

Contrary to negative films, the contrast of these films is in general high - it is thus necessary to expose to just, by knowing that there will not be (or little) of space of interpretation to pulling.

Invertible color: types & proceeded

The films of the type Ektachrome (using the Treatment E-6 defined by Kodak) are very majority today. This process is regarded as universal and usable with all the marks of film.

This said, the films of the type Kodachrome are still on sale (although not easily findable and more expensive) and use a different process.

Kodachrome

dedicated Article: Kodak Kodachrome

Ektachrome

dedicated Article: Kodak Ektachrome
The name Ektachrome is a registered trademark by Kodak and indicates professional invertible films of the mark. But by extension, it is often by this name (or by Ekta ) that one indicates films using a E6 treatment (for Ektachrome n°6 ) whatever the mark.

History

(to be supplemented…)

Historically, compared to Kodachrome, it is the introduction in 1936 by Agfa of couplers within the emulsion of sound Agfacolor Neue (contrary to the Agfacolor of 1932, similar to the Autochrome) which succeeded the simplification of the treatment.

Structure

Development

dedicated Article: Treatment E-6
The development of the film slide is close to that of the black and white (the first revealing one is a revealing black and white) and especially of the Négatif color but what makes the difference it is that the film is “buckled” (chemically or by exposure to the light) to obtain an positive image.

The first revealing one reveals the negative silver latent image of each of the 3 (or 4 in certain emulsions) layers of color. It is simple revealing for negative black and white. It is with this stage that it is possible to catch up with a certain under-exposure at the time of the catch of sight.

The bath of inversion makes it possible to expose (veil of film) the not developed parts of the first bath and thus to create in each layer an positive image.

The color appears then after the passage in a developer chromogene. The quality of chemistry, its temperature, its agitation like its age influence the neutrality of the colors. A very great care must be brought to avoid the dominant ones.

Bleaching will destroy the silver compounds to preserve only the positive layers color which form the slide. After washing and drying, the film is ready for its exploitation (projection, digitalization).

Here the table of the E6 treatment from Kodak used for the development of the films slides: Most demanding will let film take the temperature of treatment (38  °C) before plunging it in the first bath and will maintain the baths of washing (after revealing), inversion and chromogene at a temperature of 38  °C (± 1  °C).

Invertible black and white: characteristics & uses

Especially used by professional photographs (for the same invertible reasons as the color), this type of film is less and less current, as well because of the now current use of numerical as of the high price of the specialized emulsions and the difficulties (relative) for the photo hobbyist of treating oneself this film.

To obtain an invertible black and white, there are 2 methods:

  1. To use a dedicated film. Most important (Agfa Scala 200X) is treated in France by only one laboratory in Paris (Arka-Dupon, which also does it by correspondence) and is very appreciated for its returned. There exist also films less known and little distributed like the Foma R100.
  2. To use films negative black & white " classiques" supplemented by a particular treatment (like the Treatment C4, or then sometimes provided in kit by the manufacturer, like Kodak with the T-max 100). This type of treatment requires sometimes a fall of the sensitivity of film.

But with the disappearance of Agfa, only the 2nd method remains really usable - to note however that the Arka-Dupon laboratory bought an important stock of Scala 200X and that the latter thus remains there still on sale for some time.

See too

Articles on Wikipédia

External bonds

  • On the Web site Exprmntl:
    • Explanation of the development E6
    • Explanation of the process C4
  • Tutoriel for the film black inversion & white on the site Gallery-Photo .

Simple: Slide

Random links:Carentan | Lección de música | Lever (mechanical) | Rebuild off Evangelion | Harrison Page | Stephan Demol | Monastère_de_Gelati