Basic principles

Basic camera design is based on the principle of the Camera Obscura. Essentially a camera is a lightproof box with an aperture that allows light into the interior. A modern SLR (single lens reflex) camera primarily consists of a body, lens, aperture and shutter.

The lens directs the light into the camera, the aperture controls how much light reaches the film plane, the shutter controls the time the incoming light falls on the film plane and the body provides the lightproof environment for the film; supports the attachment of the lens and all the associated mechanical and electrical functions of the camera.

We use the camera to expose light sensitive film, thereby producing a latent image suitable for developing. This image when developed, is called a negative.

Exposing a balanced negative is integral to producing a good print. Good exposure is determined by combination’s of film ISO, aperture and shutter speed. Film sensitivity will be dealt with separately a little later, however it’s worth noting that a working understanding of film speed will help you determine how best to manage aperture and shutter speed combination’s.

Aperture has a dual function in photography. Whilst it is one of the factors that determines the amount of light reaching the film plane it also governs depth of field (DOF). There is also an inverse relationship between f stop number and aperture size. For example when the aperture is open to it’s maximum setting, the depth of field is the smallest e.g., f2.8.

Much is dependent on the camera/lens combination;

For example; a Canon 600D set to a focal length of 50mm and an aperture of 2.8 when focused on a subject 3m away will have an effective DOF of 30cm. This means that near focus will be 2.8m, focus 3m and far focus 3.2m. Near hyper-focal will be 23.2m, hyper-focal will be 46.5m and far hyperfocal will be infinity. Whereas at f22 for example the same settings will produce a DOF of 4m, with near focus being 1.9m, focus 3m and far focus 6m. Near hyperfocal will be 2.9m, hyperfocal will be 5.8m and far hyperfocal will be infinity. By comparison a Nikon d600 with the same settings @ f22 will yield a DOF of 13.4m with near focus being 1.6m, focus 3m and far focus 15m and at f2.8 will yield a DOF of 60cm, with near focus being 2.7m, focus 3m and far focus being 3.3m. Near hyperfocal will be 14.7m, hyperfocal will be 29.5m and far hyperfocal will be infinity.

The hyperfocal distance is defined as the focus distance which places the furthest edge of a depth of field at infinity.

All DOF involve some near and far unsharpness, even at f64 there will be fall-off at the nearest and furthermost ends of the zone of focus.

Effective use of DOF (depth of field) often requires an understanding of ‘zone of focus’, a parallel term for DOF (depth of field) but one that enables you to think about where to place the focal point within the selected depth of field. This will often be determined by how you want the image to look, i.e., whether you want to soften the foreground or background in a shot with f11 or higher selected as your DOF. This is different to thinking about using apertures like f2.8 to create an area of selective focus with the foreground or background out of focus.

Understanding ‘zone of focus’ and ideas such as placing the focal point at the beginning, mid or end point of the zone of focus within a selected DOF is part of growing in awareness as a photographer.

Using Nikon SLR’s

A variety of Nikon cameras from SLR to DSLR are available for you to use. Primarily, the preliminary course will focus on using SLR (single lens reflex) cameras. The Nikon SLR  cameras available for you vary a little but not significantly.

to be cont…..

In the interim here’s some useful reading

Understanding Camera Lenses

Camera Exposure, Aperture and ISO

Understanding Depth of Field

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