Like the magnifying glass, the telescope, the image projectors and the microscope, the camera is also considered an optical instrument. Thus, we can characterize an optical instrument as any convenient combination of optical devices, such as mirrors, prisms and lenses. Optical instruments are intended to apply, capture, provide images, etc.
There are two types of optical instruments: projection and observation. Optical projection instruments are equipment whose purpose is to conjugate real final images. Optical observation instruments are those that combine final virtual images, which are observed directly by the observer.
The camera is also an optical instrument that fits the term projection instruments . Therefore, the camera is a projection instrument whose purpose is to capture and record the real image on a film sensitive to the light that falls on it. In this article we will be more concerned with the working part of the camera.
We can simplify a camera as being basically a camera obscura with an orifice, however, in place of the orifice, a converging lens is placed, that is, a lens that converges the rays of light that pass through it to a single point. The light-sensitive photographic film is attached to the face opposite the lens. Let’s take a look at the diagram below.
In the camera it is important to know how to focus the object, in order to have a clear image on the film. If the observed object is not focused correctly, the image will be completely out of focus. This focusing is done as follows: if the object is far from the lens, it must be very close to the film and vice versa.