Photography Class Reading

Read ALL of this material and take notes on what you read. This is the basic technical information you will need to know to do well in photography. When completed take the quiz at the bottom of the section.

THE CAMERA 

A camera is a device that directs LIGHT focused by a lens or other optical system onto a photosensitive surface housed in a light-tight enclosure or BODY. In this very basic sense, these components perform the same function today that they did when photography was invented nearly 150 years ago. The first camera was a simple hole in a light tight box invented by artist / inventor Leonardo daVinci in the 1700's. In simple cameras the lens is generally of the fixed-focus variety: no provision is made to focus on objects at varying distances from the camera. More complicated cameras have a system to achieve good focus that is manually or automatically actuated, in order to vary the lens-to-focal-plane distance. (The focal plane is the point behind the lens where the image comes to focus.)  The photographic surface used in modern cameras is almost exclusively light-sensitive film Flexible roll film may be housed in a cassette or on a paper-backed spool. A gear mechanism built into the camera advances the film between exposures. On professional, large-format cameras the film is a fairly stiff sheet that is carried in a holder to be inserted into the focal-plane area after the image has been focused.  Cameras are manufactured in a variety of types and sizes. Miniature instruments producing incredibly small images are used in medical research. Commercial portrait studios may use large-format view cameras that produce a film image as large as 11 x 14 inches.  The electronics revolution has had an immense impact on camera design, making possible instruments of remarkable sophistication in almost every price range.      

THE PARTS OF THE CAMERA   

Lens

Diaphragm - Aperture  One of the two factors that determines correct film exposure is the amount of light allowed to pass through the lens. The aperture is the camera adjustment that controls how much light enters the camera. Mechanically reducing the aperture improves optical performance, particularly toward the edge of the picture, and increases the DEPTH OF FIELD, which is the zone of good focus. Most cameras use an iris-type diaphragm, which consists of a number of very thin metal blades. They are so mounted that by rotating a ring or moving a lever, the size of the lens opening can be varied. On automatic cameras the diaphragm is adjusted by a built-in mechanism to produce the optimum exposure over a wide range of lighting conditions.  The various openings of the diaphragm--called f-stops--are stamped on the lens mounting. Each change of diaphragm opening changes the amount of light passing through the lens by a factor of 2. For example, the amount of light allowed through the lens at a setting of 2 is twice the amount allowed through the lens at a setting of 2.8. The standard diaphragm settings found on most lenses are 2, 2.8, 4, 5.6, 8, 11, 16, 22, and so on. The smallest lens opening on a lens whose f-stops end in 22 is, in fact, 22.  

Shutter - second exposure control factor is the shutter, a mechanical device that acts as a gate, controlling the duration of time that light is allowed to pass through the lens and fall on the film. Two types of shutters are in general use. The leaf type, like the diaphragm, is made up of a number of thin metal blades that are opened and closed either by a spring-driven clockwork mechanism, or--in many recent models--by an electromechanical device. Shutters of this type usually have a maximum speed of 1/500th of a second.  The focal-plane shutter in modern cameras usually consists of two pieces of rubberized fabric that move across the focal plane. The spacing between the fabric edges and the speed of transit determine the effective shutter speed. Some recent models use ultrathin pieces of titanium instead of fabric. Shutters of this type are capable of very high speeds, in some cases 1/4,000th of a second. The entire shutter mechanism is independent of the optical system, and it is therefore ideal for cameras with interchangeable lenses.    

Exposure Control-  Many professional photographers still use exposure meters, which are instruments that measure light intensity, indicated what aperture and shutter speed are appropriate to the film type used, under prevailing light conditions. Completely automatic exposure control, however, is now virtually standard on all snapshot cameras, although many new professional instruments offer an automatic system that permits the photographer to retain a great deal of individual control.  On nonreflex instruments  selenium cell mounted adjacent to the lens measures the incoming light and selects a combination of lens aperture and shutter speed that will produce a negative of good quality. Single-lens reflex cameras without exception are fitted with through-the-lens metering systems (TTLs) that offer the ultimate in automated control of exposure. A light-sensing cell is located in the optical path inside the camera and gives an extremely accurate reading of the prevailing light conditions. The information is processed by an electronic circuit built into the camera, and the aperture and shutter speed are set accordingly.  The newest 35-mm cameras can use film cassettes that are magnetically encoded with numbers that tell the camera what type of film is in the cassette, and then adjust the camera speed accordingly.  

The Viewfinder -  For the photographer, the viewfinder defines the area covered by whatever lens is in use on the camera. The photographer looks through the viewfinder to frame the picture. The most primitive type is a simple wire frame mounted just over the lens. Proper eye position is determined by a vertical post mounted at the rear of the camera. The view seen through the frame with the post in the center is equal to the area covered by the lens.  The type of viewfinder in most frequent use today is actually a reversed telescope on all cameras except single and twin-lens reflex instruments. On a typical high-grade 35mm camera with interchangeable lenses, a bright line in the viewfinder outlines the area covered by the lens in use, and changes size automatically to correspond with the lenses of different focal lengths. In a single-lens reflex camera the image focused by the camera lens is reflected by a mirror onto a ground-glass screen, usually through a special prism arrangement. Twin-lens reflex cameras have two coupled lenses; one of them acts as a viewfinder and, like the single-lens reflex, reflects the image it sees on a ground-glass screen.  

Focusing Methods - On adjustable-lens cameras, a sharp picture requires accurate positioning of the lens system. Although its use has declined sharply, the optical-coupled rangefinder is one of the best methods of achieving good focus quickly. If the camera is out of focus, the user sees a double image in a portion of the viewfinder field. Focusing the lens brings the two images together, until--as the lens moves into focus--they are perfectly aligned.  In the single- and twin-lens reflex cameras, the image is visually focused on the ground glass in the viewfinder. Ground glass is used, whether or not the camera is fitted with a prism system for eye-level viewing. Because of the very slight distance between the picture-taking lens and the viewfinder lens in a twin-lens reflex camera, in close-ups the view seen by the photographer does not precisely match the view focused on the film. This very slight difference is called "parallax," and there are various devices available to correct for it.  Many modern cameras used by the casual snapshotter are fitted with automatic focusing systems. There are two general types, active and passive. In the active system, a circuit so elaborate that it is actually a complete miniature computer sends out an infrared beam. This beam bounces off the photographic subject and is reflected back to the camera. By electronically measuring the angle of the beam, the distance to the subject can be determined. A servomotor than adjusts the lens appropriately. The passive system works on the principle that an in-focus subject will show more contrast than an out-of-focus subject. A CCD light sensor  mounted behind the lens will search out the point of greatest contrast and set the lens. Single-lens reflex cameras often use this type of automatic focusing.      

CARE OF YOUR CAMERA 

A camera needs to be protected from shock and moisture. Vibrations from being put on the back of a motorcycle can shake the lens out of focus. Moisture from the ocean or from breathing on the lens can harm the special coating on the lens that protects the camera from flare from the sun. If the lens is dirty it should be cleaned with a soft cloth, preferably a special lens cleaning cloth or tissue designed for a lens. If the lens is very dirty a special lens cleaning liquid can be used that will clean the dirt without harming the coating on the lens. Extreme heat will also harm a camera and of course an old, dead battery can eat away the inside of the camera body.  Always keep the lens cap on the camera. For some cameras like the Pentax K1000 used in this class the light meter is always on unless the cap covers the lens to keep light out. To protect the lens may photographers put a skylight filter on the lens. This lens filters out ultra violet light which can mess up the exposure of a photo while. Ultra violet does not effect the colors of a photo at all and is a cheap way to protect the lens.    

Notes on composition

Definition of composition: The pleasing arrangement of subjects or objects within the picture area. It is the photographers choice of camera angle and object placement that leads the viewers eye to the center of interest. 

2. First a good composition must have a subject. The subject is the key element of design. The subject is the center of interest or the reason for taking the picture. There should only be one center of interest. It should be where the viewers eye comes to rest. Keep the composition simple to make the subject obvious.This is best done by getting CLOSE to your subject and looking at the rest of the frame to be sure that there isn't anything in it that needs to be eliminated. Keep your pictures SIMPLE including only those things that make the picture interesting. 

3. Treatment of the subject is the second part of good composition. How you arrange it within the frame is considered to be treatment. 

4. The Rule of Thirds is the main composition rule to follow. It divides the picture area into thirds both horizontally and vertically. The subject or center of interest should be placed on one of these lines for best balance in a photo. 

5. Camera angle and position has a lot to do with how the subject is viewed. Be aware of the horizon line in your picture. It should follow the rule of thirds. Be aware of objects in the background and move the camera position as needed to control what is visible in the background. 

6. Motion can be implied by the angle of lines in a composition. Horizontal or flat lines are peaceful while 45 degree or slanted lines place motion emphasis on an object. 

7. Leading lines use objects such as a fence or rail road tracks to catch the viewers eye and lead it into the subject. Leading lines can also be a row of objects such as cows that directs the viewer. Objects that are the same type but appear smaller and smaller as the go off into the distance lead the viewers eye also. 

8. Look for framing or the use of objects such as trees or door frames to surround the subject of our picture and add depth.

 9. Avoid mergers or the joining together of objects in the background with our subject. Items like telephone poles, flag poles, etc. in the background are a distraction on a 2 dimensional print while hardly noticed in real life in our 3 dimensional vision. Close one eye to view a scene and look for mergers.  10. Contrasting shapes, textures, or colors can be used to direct the viewer to the subject. The eye is naturally attracted to contrast points such as a black object in a white frame or a white object in a black frame. Lighting is important in creating light or dark areas in a print.   

PHOTOGRAPHIC MATERIALS - Analog / Film Photography

Photographic film is essentially a thin plastic base coated with an emulsion. The emulsion is composed of gelatin within which tiny particles of light-sensitive salts have been suspended. The salts used are usually silver HALIDES, such as silver iodide. The stored reaction to light (after the film has been exposed in the camera) is called the latent image and can be seen only after the film has been processed, or developed. A glass base may be coated with an emulsion for a special scientific or research purpose.  An antihalation backing is applied to the underside of the base to prevent a halo effect or flare around bright objects when light bounces back and passes through the film a second time. Overcoats are applied to the film to minimize abrasion when the film moves through the camera and when it is processed.  Because of the nature of the silver halides in the emulsion, all light-sensitive photographic emulsions are sensitive to the violet and blue end of the visible spectrum. By adding different types of sensitizing dyes to the emulsion, film can be made to react to the entire spectrum or to limited portions of it. This response to different wavelengths of light is called color sensitivity. Film that is sensitive to light over the entire visible spectrum is called panchromatic and is the type used for most general photography.  By varying the amount and type of sensitizing dye used, the film's sensitivity to light intensity, which is called emulsion speed, may be adjusted. The speed figures were devised to indicate the minimum exposure necessary to produce a specified degree of blackening of the film. The American Standards Association (ASA) is one organization that has developed a system for measuring this speed. In this system, known as the ASA Exposure Index or simply ASA, the higher the numerical rating, the faster the film's speed. Thus, a film rated at ASA 100 is twice as fast as and will require only half the exposure of a film rated at ASA 50. For the most part, the faster a film is, the more grainy it appears.

 In a film negative, those areas containing the lightest objects (highlights) will have the greatest amount of density after processing, while the darkest objects (shadows) will have relatively less. Contrast is the intermediate range of tones between the very light and very dark elements in the original photograph. A high-contrast film will record only the highlights and shadows, or just white and black, whereas a medium- or low-contrast film will also record the intermediate tones.  Black-and-white negative film generally has only one emulsion layer, which is sensitive more or less equally to all the colors in the visible spectrum. After processing, the highlights appear as solid black on the negative, the shadows as clear, and the middle tones as gray.   

COLOR - White light can be created by superimposing, or adding together, equal amounts of red, green and blue light, the additive primary COLORS. Any two of these primary colors, when combined, form yet another color, the complement, or opposite, of the third primary. For example, green and blue produce the color cyan, which is the opposite of red; red and blue produce magenta, the opposite of green; and green and red produce yellow, the opposite of blue. The colors cyan, magenta, and blue are referred to as the subtractive primaries because each represents the remaining color after one primary color has been subtracted from white light.  Color negative film emulsion is composed of three dye layers, each one sensitive to a separate component of light--red, green, or blue. During processing, these three layers form, respectively, the dye colors cyan, blue, and magenta. Thus, red will appear as cyan, green as magenta, and blue as yellow on the negative. 

PHOTO PAPER - Photographic paper is similar to film in composition with a major difference in sensitivity and base material. Put on a paper base photo paper can be coated with a plastic material called Resin Coating or RC paper that keep the chemicals from soaking into the fibers during processing. Photo paper is made sensitive only to blue light so that it can be handled under a red safelight in the darkroom. Paper contrast can be controlled by the chemical additives put into the emulsion. Most photographers purchase a single or fixed contrast paper for their use because of the rich black tones they produce. In the SCHS lab we will use a contrast #3 paper. Another type of paper is called Polycontrast that has been created so that its emulsion reacts to a purple colored light during exposure. As the color of purple gets stronger the paper contrast increases. We do not use this type of paper in the SCHS lab because of the expense of the filters needed to make the process work.

PHOTO CHEMISTRY

The photographic industry, the largest single user of silver, depends on the chemical reactions of the element.  Photographic film is composed of an acetate film upon which has been spread a thin gelatin layer, the emulsion, containing a silver halide (as well as organic and inorganic sensitizing compounds). Silver iodide is used for fast films, silver bromide for slower films and fast-printing papers, and silver chloride for most printing papers.  These silver salts are light-sensitive.    When struck with light an electron reacts with the silver ion, forming an elemental silver atom that is suspended in the gelatin emulsion;  the more light striking any portion of the film, the more elemental silver atoms are suspended.This image is not visible and is called a Latent image.  The silver and bromide ions that are photooxidized (the electron is released) represent only a very small portion of those present in the emulsion, probably only one or two per tiny crystal of AgBr (Silver Bromide).  This number is too small to be useful, so the film is bathed in a developer, which is designed to continue the oxidation in those crystals in which it has already been started by light energy but which has no effect on crystals as yet unaffected.  The film is still light-sensitive, and further exposure would cause all silver to be converted to the elemental state; therefore, it is fixed in a bath containing sodium thiosulfate.  This chemical coordinates with the silver to form ions that can be washed away, leaving a negative image from which the positive print can be made.

Photographic film processing converts the exposed but invisible image (the latent image) into a visible one. This step is mandatory before a re-creation on film of the original scene is possible. Although processing is usually carried out in total darkness, some materials used in black-and-white photography are suitable for use with an appropriate safelight--a light source of a color that does not affect the sensitive material.

Black-and-White Film Processing

In order to process black-and-white negative film, three solutions are required. The first and most important, the developer, converts the exposed portion of the silver halides in the film emulsion into black metallic silver, which is what actually forms the image . The amount of time the film is immersed in the developer solution is critical and must be accurately measured. The second step is the stop bath, or rinse. Its function is to stop the action of the developer remaining in the film. This helps to control the exact period of time the developer is allowed to work. The stop bath also helps to prevent the formation of bubbles of carbon dioxide gas on the surface of the film, which would show up as black spots in the final print.

The film is next placed into a fixing bath. This solution removes the unused silver halides in the film by forming a soluble solution of a silver salt, rendering the image permanent and insensitive to light. The fixer must then be removed either by washing the film in running water or by using some form of chemical neutralization. If this is not done, the constituents in the fixer will, in time, cause the image to fade. After washing, the film is immersed in a wetting agent, usually ethylene glycol, which reduces the surface tension of the water remaining on the film and helps it to dry without leaving any spots or marks. Finally, the film is placed in a dust-free enclosure to dry; forced air or heat may be used to accelerate the drying step.

QUESTIONS to test your knowledge