An aperture is a hole which light travels through and is used to control the amount of light reaching the film or image sensor.
Typically a fast shutter speed will require a larger aperture while a slow shutter speed will require a smaller aperture to avoid excessive exposure.
A device called a diaphragm usually serves as the aperture stop, controlling the aperture. Its main job is to control the effective diameter of the lens opening. Reducing the aperture size increases the depth of field and vice-versa which describes the extent to which subject matter lying closer than or farther from the actual plane of focus appears to be in focus.
A technical aspect strongly linked with aperture is shutter speed. The term shutter speed refers to the time a shutter is open. The amount of time of this exposure is critical to taking a good picture and having the right aperture with the correct shutter speed is equally important.
Following the adoption of a standardized way of representing aperture so that each major step exactly doubled or halved the amount of light entering the camera (f/2.8, f/4, f/5.6, f/8, f/11, f/16, etc.), a standardized 2:1 scale was adopted for shutter speed so that opening one aperture stop and reducing the shutter speed by one step resulted in the identical exposure. The agreed standards for shutter speeds are:
- 1/1000 s
- 1/500 s
- 1/250 s
- 1/125 s
- 1/60 s
- 1/30 s
- 1/15 s
- 1/8 s
- 1/4 s
- 1/2 s
- 1 s
Focus Point
n geometrical optics, a focus, also called an image point, is the point where light rays originating from a point on the object converge. Although the focus is conceptually a point, physically the focus has a spatial extent, called the blur circle. This non-ideal focusing may be caused by aberrations of the imaging optics. In the absence of significant aberrations, the smallest possible blur circle is the Airy disc, which is caused by diffraction from the optical system’s aperture. Aberrations tend to get worse as the aperture diameter increases, while the Airy circle is smallest for large apertures.
For a lens, or a spherical or parabolic mirror, it is a point onto which collimated light parallel to the axis is focused. Since light can pass through a lens in either direction, a lens has two focal points—one on each side. The distance in air from the lens or mirror’s principal plane to the focus is called the focal length.
Focal Length
The focal length of an optical system is a measure of how strongly it converges (focuses) or diverges (defocuses) light.
In telescopy and most photography, longer focal length or lower optical power is associated with larger magnification of distant objects, and a narrower angle of view. Conversely, shorter focal length or higher optical power is associated with a wider angle of view.
ISO
ISO (I.S.O.) is the abbreviation for the International organisation for standardisation, a governing body based in Europe that provides the standards for a wide variety of subjects. For photographers the key standard is Film Speed ratings.
Digital Manipulation
Digital manipulation involves editing photos using tools such as photoshop to improve and change images for the better and give them a better effect.
It can be used to create an illusion or deception to create a new effect on the picture, possibly changing the original use or meaning of the image.
