Camera Basics

The Lens
    In front of the aperture, a camera usually has a lens.  The lens are pieces of ground glass designed by a computer to collect light rays reflected from a subject and focus them into a sharp image on a segment of film.  From the point of view of equipment, it is normally the lens that gives the image its character; how sharp it appears, how much of it is in focus, the contrast, the impression of perspective, and more.  SLR (Single Lens Reflex) cameras offer a greater range of creative expression and control because of their interchangeable lenses.
     The mechanism of a lens is concerned chiefly with two functions:   focusing and changing the aperture size.  The aperture controls the amount of light passing through the lens, and at the same time the depth of field.  Depth of field is the distance range between the nearest and farthest subjects that will appear in acceptably sharp focus.  The size of the aperture is indicated by an f-number (also known as an f-stop) which is the scale of the aperture. The smaller the number, the larger the aperture, so f 1.8 is wider than f11.  Also the larger the aperture, the less depth of field, so f1.8 has less depth of field than f11.
     Focal Length
     Of all the features designed into a camera lens, none makes such an obvious difference to the image as focal length.  Practically, focal length can be thought of in terms of three types:  wide-angle, standard and telephoto.  This is normal terminology, although wide-angle lenses are short-focus, and telephoto lenses long-focus.
     There are two main effects of changing from a lens of one focal length to another: Magnification and angle of view.  One important reason for using a different focal length is to give a particular visual style and this is ultimately connected to perspective.  Yet perspective stays the same as long as the camera is not moved, regardless of what lens is used.

Aperture
   The Lens aperture shares with the shutter the control of the amount of light reaching the film.  A second major function of the aperture is the control of the depth of field.
     Remember that correct exposures come in pairs.  Your aperture (f-stop) and shutter speed work together.  A change of one f-stop equals a change of one shutter speed, and vice versa.  Once you have an accurate setting, you can speed up the shutter one stop and open the lens one stop an still have an accurate setting.  In other words, if you halve the light admitted by the aperture and double the light admitted by the shutter speed, the exposure remains the same.   You may also do just the opposite, slow the shutter and close down the lens and the exposure remains the same.
     It is best to pre-select aperture or shutter speed before making camera settings.  This is determined by your subject and lighting conditions   For example, say you need a lot of depth of field so all objects in your composition are in sharp focus.  You will need to pre-select a small aperture (Large f-stop), f-11 or higher, and then adjust the shutter speed to add or remove light that enters the camera.  If you have a lot of movement in your composition and it is important that you freeze the action, you will use shutter speed pre-selection.   Pre-select a fast shutter speed  1/125 or faster (depends on the action), then adjust your lens aperture to add or remove light that enters the camera.

Shutter Speed 1.  Shutter speed dial - adjusts the length of time the shutter is opened 2.  On most 35mm cameras, the shutter speed dial is located near the film advance lever. 3.  The B setting allows you to make exposures longer than what is marked on the shutter speed dial. 4.  The number begins at 1 or 2 and goes to 500, 1000, this will very depending on the camera. 5.  The numbers refer to fractions of a second.

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