Camera Fundamentals: Lenses, Focus, and Exposure
Camera Fundamentals
Basic Compact Camera
The target is fixed, the most frequent type of lens is a wide-angle. It has no focus ring and diaphragm, and has a lateral display.
Classic Reflex Camera
The aim is interchangeable and supports any type of lens. It has a ring focus and aperture, and a reflex viewfinder.
Viewfinder’s Objectives
The eye of the camera, lens, or set of lenses through which light enters the camera, allowing the formation of the image inside.
Luminosity
The usable space of a target, expressed as a fraction, is the luminosity. The greater this is, the greater the light that can enter the camera, and therefore, the more likely it is to take photographs.
The Focal Length
When a series of parallel rays impinge vertically on a lens, they focus after crossing it at one point called the focus. The distance between this point and the center of the lens is the focal length. The focal length matches the distance between the center and the objective plane on which the image is formed.
Types of Objectives
- Normal Objective: Focal length around 50mm, it covers an angle of 48°.
- Wide Angle: Focal length below 35mm, it covers an angle above 60°.
- Telephoto Lens: Focal length above 70mm, it covers an angle less than 35°.
- Zoom: An objective lens system with variable focal lengths.
Focus
Focus is to graduate the distance of the objective lens so that the image occurs as clearly as possible in the plane where the film is set.
The Viewfinder and Systems Approach
Side Viewfinder
With the objective, you look at a place different from that used by the camera’s objective. The focus on these cameras either does not exist, as it is not very necessary for a wide-angle lens, or is done automatically, using infrared autofocus or marks on the center of the viewfinder that are placed at the selected point.
Reflex Viewfinder
Through a pentaprism, the image that comes through the target to the viewer is not lost, thus avoiding the parallax error and allowing you to see the image with the same degree of focus as the camera itself. The focusing system is the focusing screen.
The Diaphragm
The amount of light entering a camera is controlled by a set of slides that open or close the circle through which light passes. (The opening the objective has, and the time the light is allowed to penetrate).
Depth of Field
Depth of field is the distance in front of and behind the focus point that remains sharp. (The closer the subject is approached, the greater the depth of field. The higher the focal length, the lower the depth of field).
The Shutter
Controls the time during which light enters the inside of the chamber. In compact cameras, it is situated in the center of the target and consists of a series of slides that open from the center. In SLR cameras, the shutter is not positioned on the objective, but in the body of the camera, just in front of the film. This allows the objective to be changed at any time. It consists of metal or black cloth curtains that move up and down at the time of shooting.
Relationship Between Aperture and Speed
Overexposure
The resulting photograph will be too clear, missing lines, contours, and colors.
Underexposure
The effect is the opposite: a picture that is too dark, preventing full appreciation of the characteristics of the subject.
A spectrophotometer measures the intensity of light reaching them. To shorten the time in which light penetrates the chamber, you will open the aperture in the same proportion so that the amount of light is the same. Depth of field: the higher the value of f, the greater the depth of field.
The Film
Format
The most common in amateur photography is the 35mm or universal format.
Sensitivity to Light
The speed with which the film reacts to light.
IRIS: 42 32 22 16 11 8 5.6 4 2.8 1.4 1 (less to more)
SPEED: 1″ 1/2 1/4 1/8 1/15 1/30 1/60 1/125 1/250 1/500 1/1000 1/2000 (less light to more light)
DIN: 6º 9º 12º 15º 18º 21º 24º 27º 30º
ASA: 3 6 12 25 50 100 200 400 800 (less to more)
DISTANCES: 0.5 0.75 1m 1.5 2 3 4 6 8 (in relation to the diaphragm)