Shutter Release Button The  shutter  release  button  opens  the  shutter  and initiates the exposure. Shutter Speed Dial The  shutter  speed  dial  indicates  optional  shutter speeds and sets the length of time the shutter remains open during an exposure. Shutter speeds are indicated in  fractions  of  a  second;  for  example,  60  =  1/60  of  a second (also expressed as 1/60"). The higher the number on the dial, the faster the shutter speed and the shorter the exposure. ISO Indicator The   ISO   (International   Standards   Organization) indicator  allows  you  to  compensate  for  the  particular “speed” of your film. For example, if you are shooting black-and-white film with an ISO of 400, you will set your ISO indicator to 400. The higher the ISO, the more light sensitive the film. Aperture Control The aperture control is a ring around the lens with a scale listing aperture numbers (2.8, 3.5, 4, 5.6, etc.). These  numbers  are  also  known  as  “f/stops.”  The  ring sets the f/stop on the lens to control the amount of light entering the lens. Film Rewind Knob The film rewind knob is used to rewind the film into the  cassette  (film  canister),  to  tighten  slack  in  loaded film and to open the back of the camera. You turn the knob in the direction of the arrow to rewind the film, and lift it to open the back of the camera. LENSES AND APERTURES As  noted  previously,  most  35mm  SLRs  have interchangeable lenses. The “final length” of a lens is the distance from the optical center of the lens to the final  plane  (film  plane)  when  the  camera  is  focused upon an object at itifinity. A 50mm final-length lens is considered  the  “normal”  lens  because  when  you  look through   the   viewfinder,   objects   appear   at   their approximate normal size. A smaller than normal focal length (such as 28mm) means a wider angle of view. A longer than normal final length (such as 135mm) is a telephoto lens. Focal length affects film image size. 11-6 Figure 11-5.—Comparison of the iris diaphragm of a camera lens to the iris of the human eye. The  f/stop  (aperture)  ring  controls  the  amount  of light passing through the iris diaphragm of the lens and striking  the  film.  The  higher  the  f/stop  number,  the smaller the amount of light allowed to enter the camera lens. This principle works in the same manner as the iris of the human eye (fig. 11-5). OPERATING THE 35MM SLR CAMERA LEARNING   OBJECTIVE:   Determine   the proper operating procedures for the 35mm SLR camera. The components of a 35mm SLR camera are of little consequence  if  you  do  not  know  how  to  use  them together. In this section, you will learn how to perform the  following  functions: l l l l l l l l l Loading Holding the camera Focusing the camera Setting the film speed Activating the light meter Setting the shutter speed Setting the aperture control Shooting  the  picture Unloading the film LOADING You should load the camera in subdued light (not direct sunlight) and use the following method: