Back to basics: Focus and exposure

Peter Rowlands · Issue 13, Jun/Jul 2003 · pp. 48–53

Products mentioned: Nikonos III, Nikonos IVa, Nikonos V

48 Back to basics Focus and exposure by Peter Rowlands FOCUS Most lenses can be adjusted to alter the point of focus. This is usually done by rotating the barrel of the lens to move the internal elements in relation to the film. The further away the lens is from the film, the closer the point of focus will be. A good example of this is with extension tubes on a Nikonos where the 35mm lens is placed further away from the film by putting an extension tube between the camera body and 35mm lens. With reflex cameras you can see the changing effect in the view-finder but with non-reflex cameras you have to estimate how far away you want the point of focus to be and set the lens accordingly. As we will see later, there are additional criteria which make the exactness of the point of focus much less critical. EXPOSURE There is little point in having a sharp subject if the film is incorrectly exp…