Definition

1. Aperture/F-stop- We often see on a camera brochure that says "Lens: 35-105mm f-3.5-f8". The "f-3.5-f8" is called the F-stop or the maximum aperture of the lens. This figure is derived from dividing the focal length of the lens by the aperture opening of the lens. The aperture is the opening formed by a system of metal leaves in the lens that open up and close down to control the volume of light passing through the lens. It is the lens's equivalent of the iris of our eye.
2. Aperture Priority- is a setting on some cameras that allows the user to choose a specific aperture value while the camera selects a shutter speed to match. The camera will ensure proper exposure. This is different from manual mode, where the user must decide both values, shutter priority where the user picks a shutter speed with the camera selecting the aperture to match, or program mode where the camera selects both.
3. Ambient Light- Ambient light is the available light in a room, whether by natural or mechanical sources.
4. Artificial Light- Artificial lighting is any lighting that is not sunlight.
   Generally speaking, artificial lighting is lighting which is man made, such as fluorescent, tungsten, mercury vapor, sodium vapor, halogen, compact fluorescent, et cetera. It can be turned on and off at a flick of a switch.
   There are also very special types of artificial light for specific purposes Such as infared heat lamps, ultraviolet lights for plant growth and tanning, et cetera.
   In photography, different light sources have a different color temperature which can be compensated for with special filters or simulated with special lighting. A flash simulates the light of the sun for a fraction of a second.
5. ASA/ISO/Film Speed- Film speed (ASA or ISO) is a standardized way of measuring the light sensitivity of a certain film. ISO 400 speed film is twice as sensitive to light as ISO 200 speed. Therefore, if your camera meter indicates 1/4 second shutter speed at f3.5 with ISO 200 film, it would indicate 1/8 second shutter speed at f3.5 for the same scene with ISO 400 film.
6. Bracket- Exposure bracketing is a simple technique professional photographers use to ensure they properly expose their pictures, especially in challenging lighting situations
7. Depth of Field- In optics, particularly as it relates to film and photography, depth of field (DOF) is the distance between the nearest and farthest objects in a scene that appear acceptably sharp in an image. Although a lens can precisely focus at only one distance at a time, the decrease in sharpness is gradual on each side of the focused distance, so that within the DOF, the unsharpness is imperceptible under normal viewing conditions.
8. Exposure Triangle- writing with light in Greek, and exposure is the combination of three factors that determine what the light writes… hence the Exposure Triangle.
9. How to Control Depth of Field- Three factors affect depth of field – lens aperture, distance from camera to subject and lens focal length. Aperture is most often used to control depth of field. To make as much of the scene as sharp as possible, set as small an aperture (f-stop) as the lighting will allow. To single out a subject, set as wide as aperture as possible; you’ll have to change the shutter speed to compensate in both instances.
10. Light Meter- a light meter is often used to determine the proper exposure for a photograph. Typically a light meter will include a computer, either digital or analog, which allows the photographer to determine which shutter speed and f-number should be selected for an optimum exposure, given a certain lighting situation and film speed. Light meters are also used in the fields of cinematography and scenic design, in order to determine the optimum light level for a scene. They are used in the general field of lighting, where they can help to reduce the amount of waste light used in the home, light pollution outdoors, and plant growing to ensure proper light levels.