My Science School

Printing converts the negative image of the film into a positive image on paper. Light is shone through the film onto light-sensitive paper. Passing the light through lenses makes the image larger. The print is then developed and fixed just as the film was.

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; with most papers the image density from exposure can be sufficient to not require further development, aside from fixing and clearing, though latent exposure is also usually present. The light-sensitive layer of the paper is called the emulsion. The most common chemistry was based on silver salts but other alternatives have also been used.

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 (forming a contact print) or by projecting the shadow of the negative onto the paper (producing an enlargement). The initial light exposure is carefully controlled to produce a gray scale image on the paper with appropriate contrast and gradation. Photographic paper may also be exposed to light using digital printers such as the Light-jet, with a camera (to produce a photographic negative), by scanning a modulated light source over the paper, or by placing objects upon it (to produce a photogram).

Despite the introduction of digital photography, photographic papers 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.

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After an image has been recorded on light-sensitive film in a camera, the film is moved along, so that the next photograph will be taken on a fresh piece of film. No more light must hit the exposed film until it is developed, or the picture would be spoiled. When all the photographs on a roll of film have been taken, the film is wound into its case, which is lightproof. The development process then takes place in a darkroom, or in a specially made machine.

Photographic processing or photographic development is the chemical means by which photographic film or paper is treated after photographic exposure to produce a negative or positive image. Photographic processing transforms the latent image into a visible image, makes this permanent and renders it insensitive to light.

All processes based upon the gelatin-silver process are similar, regardless of the film or paper’s manufacturer. Exceptional variations include instant films such as those made by Polaroid and thermally developed films. Kodachrome required Kodak’s proprietary K-14 process. Kodachrome film production ceased in 2009, and K-14 processing is no longer available as of December 30, 2010. llfochrome materials use the dye destruction process.

All photographic processing use a series of chemical baths. Processing, especially the development stages, requires very close control of temperature, agitation and time.

1. The film may be soaked in water to swell the gelatin layer, facilitating the action of the subsequent chemical treatments.


2. The developer converts the latent image to macroscopic particles of metallic silver.


3. A stop bath, typically a dilute solution of acetic acid or citric acid, halts the action of the developer. A rinse with clean water may be substituted.


4. The fixer makes the image permanent and light-resistant by dissolving remaining silver halide. A common fixer is hypo, specifically ammonium thiosulfate.


5. Washing in clean water removes any remaining fixer. Residual fixer can corrode the silver image, leading to discolouration, staining and fading.

The washing time can be reduced and the fixer more completely removed if a hypo clearing agent is used after the fixer.

1. Film may be rinsed in a dilute solution of a non-ionic wetting agent to assist uniform drying, which eliminates drying marks caused by hard water. (In very hard water areas, a pre-rinse in distilled water may be required – otherwise the final rinse wetting agent can cause residual ionic calcium on the film to drop out of solution, causing spotting on the negative.)


2. Film is then dried in a dust-free environment, cut and placed into protective sleeves.

Once the film is processed, it is then referred to as a negative. The negative may now be printed; the negative is placed in an enlarger and projected onto a sheet of photographic paper. Many different techniques can be used during the enlargement process. Two examples of enlargement techniques are dodging and burning. Alternatively (or as well), the negative may be scanned for digital printing or web viewing after adjustment, retouching, and/or manipulation.

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A camera is a lightproof box containing light-sensitive film. To take a picture, the photographer presses a button to open a shutter and let light pass through the aperture, a hole in the front of the camera. The camera’s lens focuses the light so that it forms a sharp image on the photographic film, just as the lenses in our eyes focus the light onto our retinas. Then the shutter closes again so that no more light reaches the film. The whole process usually takes just a fraction of a second.

A still film camera is made of three basic elements: an optical element (the lens), a chemical element (the film) and a mechanical element (the camera body itself). As we'll see, the only trick to photography is calibrating and combining these elements in such a way that they record a crisp, recognizable image.

There are many different ways of bringing everything together. In this article, we'll look at a manual single-lens-reflex (SLR) camera. This is a camera where the photographer sees exactly the same image that is exposed to the film and can adjust everything by turning dials and clicking buttons. Since it doesn't need any electricity to take a picture, a manual SLR camera provides an excellent illustration of the fundamental processes of photography.

The optical component of the camera is the lens. At its simplest, a lens is just a curved piece of glass or plastic. Its job is to take the beams of light bouncing off of an object and redirect them so they come together to form a real image -- an image that looks just like the scene in front of the lens.

But how can a piece of glass do this? The process is actually very simple. As light travels from one medium to another, it changes speed. Light travels more quickly through air than it does through glass, so a lens slows it down.

When light waves enter a piece of glass at an angle, one part of the wave will reach the glass before another and so will start slowing down first. This is something like pushing a shopping cart from pavement to grass, at an angle. The right wheel hits the grass first and so slows down while the left wheel is still on the pavement. Because the left wheel is briefly moving more quickly than the right wheel, the shopping cart turns to the right as it moves onto the grass.

The effect on light is the same -- as it enters the glass at an angle, it bends in one direction. It bends again when it exits the glass because parts of the light wave enter the air and speed up before other parts of the wave. In a standard converging, or convex lens, one or both sides of the glass curves out. This means rays of light passing through will bend toward the center of the lens on entry. In a double convex lens, such as a magnifying glass, the light will bend when it exits as well as when it enters.

This effectively reverses the path of light from an object. A light source -- say a candle -- emits light in all directions. The rays of light all start at the same point -- the candle's flame -- and then are constantly diverging. A converging lens takes those rays and redirects them so they are all converging back to one point. At the point where the rays converge, you get a real image of the candle. In the next couple of sections, we'll look at some of the variables that determine how this real image is formed.

The first person to take a photograph was a Frenchman, Joseph Nicephore Niepce, in 1822. However, as is often the case with new inventions, many other scientists had been experimenting with light, lenses and light-sensitive chemicals. Working with Niepce was a man called Louis Daguerre, who later improved on Niepce’s process. Some early photographs were called daguerreotypes.

Around 1717 Johann Heinrich Schulze captured cut-out letters on a bottle of light-sensitive slurry, but he apparently never thought of making the results durable. Around 1800 Thomas Wedgwood made the first reliably documented, although unsuccessful attempt at capturing camera images in permanent form. His experiments did produce detailed photograms, but Wedgwood and his associate Humphry Davy found no way to fix these images.

In the mid-1822s, Nicephore Niepce first managed to fix an image that was captured with a camera, but at least eight hours or even several days of exposure in the camera were required and the earliest results were very crude. Niépce's associate Louis Daguerre went on to develop the daguerreotype process, the first publicly announced and commercially viable photographic process. The daguerreotype required only minutes of exposure in the camera, and produced clear, finely detailed results. The details were introduced to the world in 1839, a date generally accepted as the birth year of practical photography. The metal-based daguerreotype process soon had some competition from the paper-based calotype negative and salt print processes invented by William Henry Fox Talbot and demonstrated in 1839 soon after news about the daguerreotype reached Talbot. Subsequent innovations made photography easier and more versatile. New materials reduced the required camera exposure time from minutes to seconds, and eventually to a small fraction of a second; new photographic media were more economical, sensitive or convenient. Since the 1850s, the collodion process with its glass-based photographic plates combined the high quality known from the Daguerreotype with the multiple print options known from the calotype and was commonly used for decades. Roll films popularized casual use by amateurs. In the mid-20th century, developments made it possible for amateurs to take pictures in natural color as well as in black-and-white.

The commercial introduction of computer-based electronic digital cameras in the 1990s soon revolutionized photography. During the first decade of the 21st century, traditional film-based photochemical methods were increasingly marginalized as the practical advantages of the new technology became widely appreciated and the image quality of moderately priced digital cameras was continually improved. Especially since cameras became a standard feature on smartphones, taking pictures (and instantly publishing them online) has become a ubiquitous everyday practice around the world.

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Glueing, sewing or stapling pages together and placing them within a cover is called binding. Several pieces of card and paper are required to bind a hardback book. It is also possible to add bookmark ribbons and little pieces of fabric called headbands at the top and bottom of the spine (back) of the book.

A hardcover or hardback (also known as hardbound, and sometimes as case-bound) book is one bound with rigid protective covers (typically of binder’s board or heavy paperboard covered with buckram or other cloth, heavy paper, or occasionally leather). It has a flexible, sewn spine which allows the book to lie flat on a surface when opened. Following the ISBN sequence numbers, books of this type may be identified by the abbreviation Hbk.

Hardcover books are often printed on acid-free paper, and they are much more durable than paperbacks, which have flexible, easily damaged paper covers. Hardcover books are marginally more costly to manufacture. Hardcovers are frequently protected by artistic dust jackets, but a "jacketless" alternative has increased in popularity: these "paper-over-board" or "jacketless hardcover" bindings forgo the dust jacket in favor of printing the cover design directly onto the board binding.

Hardcovers typically consist of a page block, two boards, and a cloth or heavy paper covering. The pages are sewn together and glued onto a flexible spine between the boards, and it too is covered by the cloth. A paper wrapper, or dust jacket, is usually put over the binding, folding over each horizontal end of the boards. Dust jackets serve to protect the underlying cover from wear. On the folded part, or flap, over the front cover is generally a blurb, or a summary of the book. The back flap is where the biography of the author can be found. Reviews are often placed on the back of the jacket. Many modern bestselling hardcover books use a partial cloth cover, with cloth covered board on the spine only, and only boards covering the rest of the book.

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Pages in a book are not printed one by one. They are printed on huge sheets of paper that then pass through another machine to be folded. When the book is bound (put into its cover), the edges of the pages are cut on a guillotine. A piece of paper folded in half creates four pages. Larger sheets of paper are folded to make 16, 32 or even 64 pages.

Most booklets are created with the Saddle-Stitch binding method. This method uses printed sheets that are folded and nested one inside the other and then stapled through the fold line with wire staples. The staples pass through the folded crease from the outside and are clinched between the centermost pages. The result is a very simple yet professional looking document.

Despite its relative simplicity, saddle-stitch booklets often pose a challenge for someone new to graphic design. This is because the page set-up for saddle-stitched booklets requires a different approach than for other types of bound books.

Saddle-stitched booklets are constructed of folded sheets. As such, each folded sheet joined within the finished booklet will form four pages of the booklet. This means the page count of every saddle-stitched booklet must always be a multiple of four (4). It is not possible to create a 7-page, 10-page, or 25-page saddle-stitched booklet. All saddle-stitched booklets must contain 4 pages, 8 pages, 12 pages, 16 pages, 20 pages, 24 pages and so on. Even if a page in the booklet is blank, it still counts as a page.

Needless to say, creating the layout file properly at the onset will help optimize your booklet’s press run…saving time, effort, and expense for all involved. The software you use to create the booklet will likely give you file layout choices, such as Reader Spreads or Printer Spreads. Because printing presses and production methods vary from print shop to print shop, do not automatically set up your booklet file in a particular spread or configuration without first consulting the printer you intend to use for producing your booklet.

A typeface is an alphabet that has been specially designed for printing. It can usually be used in a variety of sizes and styles. The typeface chosen has a huge effect on how a printed page looks. Some typefaces are designed to be easy to read. Others are meant to catch the eye in headings and titles. Today, computers make it easy to manipulate type, stretching it or squashing it, for example, to create special effects. It is also easy to adapt typefaces or create your own. Each set of letters, numbers and symbols in a type-face is called a font.

A typeface is a set of characters of the same design. These characters include letters, numbers, punctuation marks, and symbols. Some popular typefaces include Arial, Helvetica, Times, and Verdana. While most computers come with a few dozen typefaces installed, there are thousands of typefaces available. Because they are vector-based (not bitmaps), typefaces can be scaled very large and still look sharp. The term "typeface" is often confused with “font,” which is a specific size and style of a typeface. For example, Verdana is a typeface, while Verdana 10 pt bold is a font. It's a small difference, but is good to know.

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The page to be printed passes between inked rollers or plates four times, each time with a different coloured ink being used. In order to make sure that the final image is clear and sharp, the four printings must line up exactly on top of each other. This is known as registration. Registration marks, at the corners of a page, help the printer to position the images accurately. You may have seen a strip of coloured shapes on the edge of a printed food- packet. These also enable the printer to see at a glance if the four printings have been properly positioned.

Four color process printing uses four ink colors – Cyan, Magenta, Yellow and Black. These four colors are applied one after the other on a printing press. They overlap each other in various concentrations on the paper to create the visual effect we know as full color printing. Because these four colors combine to make an image, the proper registration of these colors is crucial to produce a sharp image. Even a slight position shift in one of the four colors will cause the printed image to appear blurred or fuzzy.

For the same reason as above, proper registration is also a concern for two-color and three-color printing. One-color printing is not concerned with ink registration since only one ink color is used (but like all printing jobs, the ink must be properly registered to the paper so that the image transfers to its intended location – i.e., not closer to one edge of the paper than intended).

A term related to ink registration is Close Registration, which means that the printed image has two or more ink colors that touch or are very near each other. By its nature, four color process printing always has close registration. Two-color and three-color printing may or may not have close registration, it just depends on the intended design. Jobs with close registration should be printed in a single pass through a printing press to ensure the ink colors align properly with each other.

Proper registration is also an important consideration for multi-part forms. Each ply of the form must be assembled in the same relative position so entries made on the top ply transfer properly to each subsequent ply. Have you ever filled out a multi-part form only to notice that what you wrote on the top was slightly out of position on a different ply? This is because the form’s ply-to-ply registration was off.

Some printed images use one solid colour. These words are printed in solid black ink, for example. The dots are so close together that no background colour shows through. Using increasingly widely spaced dots creates the impression of paler tones of grey.

The color model (process color, four color) is a subtractive color model, based on the CMY color model, used in color printing, and is also used to describe the printing process itself. CMYK refers to the four ink plates used in some color printing: Cyan, Magenta, Yellow, and Key (black).

The CMYK model works by partially or entirely masking colors on a lighter, usually white, background. The ink reduces the light that would otherwise be reflected. Such a model is called subtractive because inks "subtract" the colors red, green and blue from white light. White light minus red leaves cyan, white light minus green leaves magenta, and white light minus blue leaves yellow.

In additive color models, such as RGB, white is the "additive" combination of all primary colored lights, while black is the absence of light. In the CMYK model, it is the opposite: white is the natural color of the paper or other background, while black results from a full combination of colored inks. To save cost on ink, and to produce deeper black tones, unsaturated and dark colors are produced by using black ink instead of the combination of cyan, magenta, and yellow.

With CMYK printing, half-toning (also called screening) allows for less than full saturation of the primary colors; tiny dots of each primary color are printed in a pattern small enough that humans perceive a solid color. Magenta printed with a 20% halftone, for example, produces a pink color, because the eye perceives the tiny magenta dots on the large white paper as lighter as and less saturated than the color of pure magenta ink.

Without half-toning, the three primary process colors could be printed only as solid blocks of color, and therefore could produce only seven colors: the three primaries themselves, plus three secondary colors produced by layering two of the primaries: cyan and yellow produce green, cyan and magenta produce blue, yellow and magenta produce red (these subtractive secondary colors correspond roughly to the additive primary colors), plus layering all three of them resulting in black. With half-toning, a full continuous range of colors can be produced.

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However colourful a page in a book may be, it is probably made up of only four colours. Tiny dots of yellow, blue, red and black inks are used to print the page. The dots are so small that they cannot usually be seen with the naked eye. Instead, they “mix” visually to form all the colours on the final page.

4-Color Process is the most widely used method for printing full-color images. All commercial printers use the 4-Color Process method for projects that contain multi-colored designs or photographs. This includes books, catalogs, manuals, magazines, brochures, postcards and any other printed items that contain full color images. Because of its widespread use in both offset and digital printing, 4-Color Process is much more affordable today than in years past.

As its name implies, 4 ink colors are used in 4-Color Process printing. These four colors are Cyan, Magenta, Yellow, and Black…which are known collectively as CMYK. In fact, 4-Color Process printing is frequently referred to as CMYK printing. It is also known as Four Color Printing, 4CP, Full Color Printing, or simply Process Printing.

Full-color images are created on the printing press by applying separate layers of the Cyan, Magenta, Yellow and Black inks. Thousands of colors can be reproduced by overlapping these CMYK colors in various concentrations. Applied as tiny dots on the paper (or other substrate), the four CMYK colors combine to create the visual effect we know as full color printing. Look at the photographs in a printed magazine or brochure under strong magnification and you will see the distinct CMYK dots.

No. Sometimes there are certain colors that cannot be reproduced exactly using the 4-Color Process method. In this case, PMS colors (also known as Spot colors or Pantone Matching System colors) are used to create a particular color. PMS colors are specific color formulas that will reproduce accurately in print. Instead of simulating colors by layering multiple ink colors with the CMYK 4-Color Process, PMS ink colors are pre-mixed from existing color formulas and assigned a standardized number.

PMS colors are often used in conjunction with the four CMYK process colors on certain projects. These are referred to as 5-color or 6-color projects because they use the four CMYK colors plus one or two PMS colors (or more) for certain elements of the design, such as a corporate logo. PMS colors generally involve an upcharge, so they are usually reserved for projects that require a specific color (or colors) that cannot be reproduced accurately by layering the four CMYK colors.

Only a small percentage of full-color projects necessitate the addition of PMS colors because most graphic designers refer to a Pantone Process Book and then use the process color formula that is closest to the desired PMS Spot color. So if you intend to print the entire piece using CMYK 4-color process, it is important that you don’t designate PMS Spot colors in your artwork design. Otherwise when your PMS Spot color is converted to a CMYK process color to create printed output, it could yield a result you weren’t anticipating. If in doubt, always consult with your printer before getting too deep into your project.

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Printing—producing identical copies of a picture or piece of writing by pressing an inked block onto a surface — was introduced by the Chinese over a thousand years ago. However, the breakthrough of movable type, which meant that a new block could be made up from existing pieces of type, without having to carve it from scratch, was developed in 1438 by Johannes Gutenberg, in Germany. This was still a fairly slow, manual method, although much faster than the alternative of writing documents out by hand. It was not until the invention of steam and, later, electrical machinery to power the presses that documents could be printed rapidly on a large scale.

Nearly 600 years before Gutenberg, Chinese monks were setting ink to paper using a method known as block printing, in which wooden blocks are coated with ink and pressed to sheets of paper. One of the earliest surviving books printed in this fashion — an ancient Buddhist text known as "The Diamond Sutra" — was created in 868 during the Tang (T'ang) Dynasty (618-909) in China. The book, which was sealed inside a cave near the city of Dunhuang, China, for nearly a thousand years before its discovery in 1900, is now housed in the British Library in London.

The carved wooden blocks used for this early method of printing were also used in Japan and Korea as early as the eighth century. Private printers in these places used both wood and metal blocks to produce Buddhist and Taoist treatises and histories in the centuries before movable type was invented.

An important advancement to woodblock printing came in the early eleventh century, when a Chinese peasant named Bi Sheng (Pi Sheng) developed the world's first movable type. Though Sheng himself was a commoner and didn't leave much of a historical trail, his ingenious method of printing, which involved the production of hundreds of individual characters, was well-documented by his contemporary, a scholar and scientist named Shen Kuo.

But all that changed in the middle of the 15th century, when Johannes Gutenberg established himself as a goldsmith and craftsman in Strasbourg, Germany.

Like Bi Sheng, Wang Chen and Baegun before him, Gutenberg determined that to speed up the printing process, he would need to break the conventional wooden blocks down into their individual components — lower- and upper-case letters, punctuation marks, etc. He cast these movable blocks of letters and symbols out of various metals, including lead, antimony and tin. He also created his own ink using linseed oil and soot — a development that represented a major improvement over the water-based inks used in China.

But what really set Gutenberg apart from his predecessors in Asia was his development of a press that mechanized the transfer of ink from movable type to paper. Adapting the screw mechanisms found in wine presses, papermakers' presses and linen presses, Gutenberg developed a press perfectly suited for printing. The first printing press allowed for an assembly line-style production process that was much more efficient than pressing paper to ink by hand. For the first time in history, books could be mass-produced — and at a fraction of the cost of conventional printing methods.

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