Photographic Paper

                                     In this Article we will discuss about Photographic Paper.Photographic paper is a Paper Coated with a light-sensitive chemical formula, used for making Photographic prints. When photographic paper is exposed to light it captures a latent image that is then developed to form a visible image. The light-sensitive layer of the paper is called the emulsion.

The print image is traditionally produced by interposing a photographic negative between the light source and the paper, either by direct contact with a large negative or by projecting the shadow of the negative onto the paper (producing an enlargement). The initial light exposure is carefully controlled to produce a grey scale image on the paper with appropriate contrast and gradation. Photographic paper may also be exposed to light using digital printers such as the lightjet, with a camera by scanning a modulated light source over the paper, or by placing objects upon it.

Despite the introduction of digital photography, photographic papers and are still sold commercially. Photographic papers are manufactured in numerous Standard Sizes,Paper Weights and Surface Finishes. A range of emulsions are also available that differ in their light sensitivity, color response and the warmth of the final image. Color Papers are also available for making Color Images.

                                                                           

                                                                        History

The effect of light in darkening a prepared paper was discovered by M. Charles in 1800 or by Thomas Wegdwoodin 1802. Photographic papers have been used since the beginning of all negative–positive.

After the early days of photography, papers have been manufactured on a large scale with improved consistency and greater light sensitivity.

Types of Photographic Paper

Photographic papers fall into one of three sub-categories:

• Papers used for negative-positive processes. This includes all current Black and white papers and chromogenic color papers.
• Papers used for positive-positive processes in which the "film" is the same as the final image
• Papers used for positive-positive film-to-paper processes where a positive image is enlarged and copied onto a photographic paper.

                                                                 Structure

All photographic papers consist of a light-sensitive emulsion, consisting of silver halide salts suspended in a colloidal material - usually gelatin- coated onto a paper, resin coated paper or polyester support. In black-and-white papers, the emulsion is normally sensitised to blue and green light, but is insensitive to wavelengths longer than 600 nm in order to facilitate handling under red or orange safelightning. In Chromogenic color papers, the emulsion layers are sensitive to red,green and blue light, respectively producing cyan,magenta and yellow dye during processing.

                                                              Base materials

Modern black and white papers are coated on a small range of bases;baryta-coated paper, resin-coated paper or polyester. In the past, linen has been used as a base material.

                                            Fiber-based papers (FB)

Fiber-based (FB or Baryta) photographic papers consist of a paper base coated with baryta. Tints are sometimes added to the baryta to add subtle color to the final print; however most modern papers use optical brightners to extend the paper's tonal range. Most fiber-based papers include a clear hardened gelatin layer above the emulsion which protects it from physical damage, especially during processing. This is called a supercoating. Papers without a supercoating are suitable for use with the bromoil process. Fiber-based papers are generally chosen as a medium for high-quality prints for exhibition, display and archiving purposes. These papers require careful processing and handling, especially when wet. However, they are easier to tone,hand-color and retouch than resin-coated equivalents.

   

              

                                                           Resin-coated papers (RC)

The paper base of resin-coated papers is sealed by two polyethene layers, making it impenetrable to liquids. Since no chemicals or water are absorbed into the paper base, the time needed for processing, washing and drying durations are significantly reduced in comparison to fiber-based papers. Resin paper prints can be finished and dried within twenty to thirty minutes. Resin-coated papers have improved dimensional stability, and do not curl upon drying.

                                                                     Color papers

All color photographic materials available today are coated on either RC (resin coated) paper or on solid polyester. The photographic emulsion used for color photographic materials consists of three color emulsion layers along with other supporting layers. The color layers are sensitised to their corresponding colors. Although it is commonly believed that the layers in negative papers are shielded against the intrusion of light of a different wavelength than the actual layer by color filters which dissolve during processing, this is not so. The color layers in negative papers are actually produced to have speeds which increase from cyan (red sensitive) to magenta (green sensitive) to yellow (blue sensitive), and thus when filtered during printing, the blue light is "normalized" so that there is no crosstalk. Therefore the yellow (blue sensitive) layer is nearly ISO 100 while the cyan (red) layer is about ISO 25. After adding enough yellow filtration to make a neutral, the blue sensitivity of the slow cyan layer is "lost".

In negative-positive print systems, the blue sensitive layer is on the bottom, and the cyan layer is on the top. This is the reverse of the usual layer order in color films.

The emulsion layers can include the color dyes, as in Ilfochrome; or they can include color couplers, which react with color developers to produce color dyes, as in type c prints or chromogenic negative–positive prints. Type R prints, which are no longer made, were positive–positive chromogenic prints.

Photographic Film

This article is mainly concerned with still photography film.

Photographic film is a sheet of plastic coated with an emulsion containing light-sensitive silver halide salts with variable crystal sizes that determine the sensitivity, contrast and resolution of the film. When the emulsion is sufficiently exposed to light, it forms a latent (invisible) image. Chemical processes can then be applied to the film to create a visible image, in a process called film developing.

In black-and-white photographic film there is usually one layer of silver salts. When the exposed grains are developed, the silver salts are converted to metallic silver, which blocks light and appears as the black part of the film negative.

Color film uses at least three layers. Dyes, which adsorb to the surface of the silver salts, make the crystals sensitive to different colors. Typically the blue-sensitive layer is on top, followed by the green and red layers. During development, the exposed silver salts are converted to metallic silver, just as with black-and-white film. But in a color film, the by-products of the development reaction simultaneously combine with chemicals known as color couplers that are included either in the film itself or in the developer solution to form colored dyes. Because the by-products are created in direct proportion to the amount of exposure and development, the dye clouds formed are also in proportion to the exposure and development. Following development, the silver is converted back to silver salts in the bleach step. It is removed from the film in the fix step. This leaves behind only the formed color dyes, which combine to make up the colored visible image.

Newer color films, like Kodacolor II, have as many as 12 emulsion layers, with upwards of 20 different chemicals in each layer.

Due to film photography's long history of widespread use, there are now around one trillion pictures on photographic film or Photographic Paper in the world, enough to cover an area of around ten thousand square kilometres (4000 square miles), about half the size of Wales.

First Camera photography

Invented in the first decades of the 19th century, photography (by way of the camera) seemed able to capture more detail and information than traditional mediums, such as painting and sculpting. Photography as a usable process goes back to the 1820s with the development of chemical photography. The first permanent Photoetching was an image produced in 1822 by the French inventor Nicephore Niepce, but it was destroyed by a later attempt to duplicate it. Niépce was successful again in 1825. He made the first permanent photograph from nature with a camera obscura in 1826.

Because his photographs took so long to expose (eight hours), he sought to find a new process. Working in conjunction with Louis Daguerre, they experimented with silver compounds based on a Johann henrich Schultz discovery in 1816 that a silver and chalk mixture darkens when exposed to light. Niépce died in 1833, but Daguerre continued the work, eventually culminating with the development in 1837. Daguerre took the first ever photo of a person in 1838 when, while taking a daguerreotype of a Paris street, a pedestrian stopped for a shoe shine, long enough to be captured by the long exposure (several minutes). Eventually, France agreed to pay Daguerre a pension for his formula, in exchange for his promise to announce his discovery to the world as the gift of France, which he did in 1839.

Passion of Photography

First of we will discuss about what is Passion?
Answer-Passion is a very strong feeling about a person,thing,game etc. Passion is a emotion compelling feeling or desire for something.The term is also often applied to a lively or eager interest in or admiration for a proposal, cause, or activity or love – to a feeling of unusual excitement,enthusiasm or compelling emotion, a positive affinity or love, towards a subject. It is particularly used in the context of romance or sexual desire though it generally implies a deeper or more encompassing emotion than that implied by the term lust.

In this we will discuss about a Photography: A Passion.

Photography is the art,science and practice of creating durable images by recording light  or other elctromagnetic radiation, either chemically by means of a light-sensitive material  such as photographic films, or electronically by means of an image sensor. Typically, a lens  is used to focus the light reflected or emitted from objects into a real image on the light -sensitive  surface inside a camera during a timed exposer. The result in an electronic image sensor is  an electrical charge at each pixel, which is electronically processed and stored in a digital  image  file for subsequent display or processing. The result in a photographic emulsion is an invisible latent image, which is later chemically  developed into a visible image, either negative or positive depending on the purpose of  the photographic material and the method of processing. A negative image on film is  traditionally  used to photographically create a positive image on a paper base, known as a print,  either by  using an enlarger or by contact printing.Photography has many uses for business, science, manufacturing,art,recreational purposes,and mass communication.