Discuss how the light reflected from a subject through the lens to a focal plane will produce an image on light sensitive materials. The pinhole camera is an example of this type of camera.

The basic leaf shutter and simple film advance system should be explained at this point.

Demonstrate that as the shutter speed is increased or decreased by one step, the amount of time that light can enter the camera is halved or doubled. (e.g. 1/125th second allows twice the light to reach the film allowed by 1/250th second). The minimum shutter speed that can be successfully handheld is about 1/30th of a second. The slightest camera movement will cause the image on the film to be blurred. In situations when a moving subject is panned the background will be blurred suggesting motion. Conversely, intentionally holding the camera still will blur a moving subject if slow shutter speeds are used. To take pictures at slower shutter speeds use a tripod. Have the students watch a moving shutter in an opened camera. This will make the fractional time concept of shutter speed easier to understand.

Explain and demonstrate the differences between focal plane and leaf shutters and the advantages of the different types.

The f in f-stop refers to the focal length of a lens. For example a lens with a focal length of 50mm opened to a diameter of 6mm will produce an aperture (or f- stop) of f/ 8 or 1/8th of the focal length of that lens.

Discuss f stop as the measure of aperture opening. Explain that as the lens is adjusted from f /2.8 to f /4 the area of the aperture is decreased by half; f /2.8 will allow twice as much light as f /4 to reach the film due to larger aperture area.

The camera shutter speeds and f-stop settings can be paired and are known as equivalent exposure settings. For example, an exposure of 1/125th of a second with an aperture of f-11 will produce an image with the same exposure on the film as the camera set at 1/60th of a second with an aperture of f-16.

The aperture and shutter speed pairs that produce equivalent film exposure create the same image density on the film. This is called the Law of Reciprocity. It states, the resulting film density for a particular shutter speed and aperture setting will produce the same film density when the aperture is halved and the shutter speed doubled, provided the same subject and lighting are compared. The law fails at very long or short exposures and delivers less density on the film than might be expected. Reciprocity failure can be corrected by increasing the exposure time or aperture.

It is important that students understand that using f /8 @ 1/250 will allow the same amount of light to pass through the lens as f /11 @ 1/125.

The larger the lens aperture (f/8 has a larger area than f/11) the faster the shutter speed will need to be due to the larger lens opening area for the light to enter the camera.

Have the students make a series of exposures changing the aperture and then setting the shutter speed to correspond for a correct exposure. The resulting images will have the same density but different depths of field.

Discuss the various methods that are used to ensure the image is in sharp focus.

There are a number of different focusing screens available depending on camera style and format.

Some electronic cameras will automatically advance the film to the first frame whereas other cameras will require manually advancing the film with the shutter advance lever and the shutter release.

Remind students to rewind the film fully before they open the camera to remove the film cassette.

Film speed is a measure of light sensitivity and is indicated by the International Standards Organization number (ISO), formerly called the American Standards Association (ASA) or Deutsche Industrie Normen (DIN) number. (See Module 4, Learning Objective 3 in this guide.)

Electronic cameras will set the film speed according to the coding information that is printed on the film cassette. Cassettes that are used for bulk loading film may not be coded or the code may not match the film in the cassette. See the owner's manual for instructions on setting the film speed for uncoded cassettes.

The students may need to review aperture and shutter speed in order to understand how the relationship between the two affects the amount of light that enters the camera. (TL)

Have the students practice setting the light meter using a variety of light and dark subjects to observe the differences in exposure times and aperture openings and the relationship between them.

The depth of field (range of acceptable sharpness between the nearest and furthest subjects in the exposure) depends on the aperture selected, how distant the main subject is from the camera and the focal length of the lens being used.

Have students select a subject with a number of elements positioned at different locations within the subject area. Focus on an object in the center of the subject group, then by changing only the aperture (or f-stop), photograph the scene with a large aperture. Then expose a second frame using the same focus and a small aperture. Have the students compare the resulting photographs.

The students can also use the aperture setting on the lens barrel to establish the point to place the infinity distance symbol. This is called the hyper-focal distance and provides the minimum distance where infinity will be within the depth of field (in focus). This is valuable when there is no time to tight focus but the subject is within the range of the current depth of field setting.

These controls might include the preview control, motor drive, tripod mount, electronic flash hot shoe, rewind crank and electronic priority features, plus others, depending on the type of camera being used by the students.

Shooting a short roll of bulk loaded film with eight frames is sufficient to see if students understand the use of camera controls (for a 35mm camera, for example).

Suggest a variety of subjects, perhaps a landscape, a close-up, a well lit (bright sunlight) and a dimly lit (shadow) situation, a moving subject and a portrait.

Some cameras are very automated. Students need to learn that they can direct some automatic systems. Show examples where photographers have overexposed or underexposed a subject, used a fast shutter speed to freeze motion or chosen a specific f stop to control the depth-of-field.

Calendar photography is a good source of materials for discussions around camera settings and the reasons for the setting selection.

The priorities to be examined should include shutter speed and aperture settings. Discuss the effect of choosing one system as it relates to the other in terms of the results obtained when the same scene is exposed once for aperture priority and again with shutter priority.

Students can choose aperture priority modes that allow them to take pictures at the f stop they prefer (see above discussion of depth-of-field), or they can choose the shutter speed priority mode to shoot at the shutter speed they prefer.