WK 02

PHOTOGRAPHY TERMS

SHUTTER SPEED 
Shutter speed is a photography term that indicates the length of time the shutter is open to allow light exposure to the film or image sensor. Used in conjunction with aperture size (f-stops), shutter speed determines total exposure and can be changed to create different effects. Shutter speed is measured in seconds, typically fractions of seconds. Shutter speed is adjusted automatically when a camera is being used in automatic mode. However, shutter speed can be adjusted manually on most SLR film and digital cameras. Conditions that typically account for determining shutter speed include lighting and movement. A slower shutter speed is used in low lighting, while a short, or quick, shutter speed is typically used to capture moving objects. To create dramatic effects, such as intentional blurring or other artistic effects, the shutter speed may be adjusted to a typical speeds for the given conditions.


APERTURE
The main function of a camera lens is to collect light. The aperture of a lens is the diameter of the lens opening and is usually controlled by an iris. The larger the diameter of the aperture, the more light reaches the film / image sensor.
Aperture is expressed as F-stop, e.g. F2.8 or f/2.8. The smaller the F-stop number (or f/value), the larger the lens opening (aperture).

Note: Many camera user manuals today will refer to the aperture in terms of "aperture value" instead of f/value. I'm not sure when this trend started but don't get confused between "aperture" and "aperture value." Aperture value" is simply another way of saying f/value.]
In practice, unless you are dealing with a fixed-aperture lens (many simple point-and-shoot cameras have only one fixed aperture), the aperture of a lens is usually expressed as a range of fstops.
When you read the specifications of a camera, the aperture may be expressed in a number of different ways, the following three being the most common:

• Maximum Aperture:

Max. Aperture

F2.8

This simply states that the maximum aperture for the lens is F2.8.

• Aperture Range:

Aperture Range

F2.8-F8.0

This states the max. and min. aperture, the assumption being that there are standard increments between them.

• Maximum Wide-Angle and Telephoto Apertures:

Aperture

F2.8-3.5 or F2.8(W)-F3.5(T)

This gives the max. aperture for the wide-angle (F2.8) and telephoto (F3.5) focal lengths of a zoom lens.

It is usually not too difficult to figure out that a stated range deals with maximum apertures and not max and min apertures: the mimimum aperture should be quite small at F8, F11, F16 or F22.
A "fast" lens is one that has a large maximum aperture (F2.4, F2.0 for current digital cameras; F1.4, F1.2 for 35mm film cameras).


So, which lens has a larger opening (aperture): one with an aperture of F1.8 or one with an aperture of F2.8?
Ans : F1.8 (remember, the smaller the F-stop, the larger the aperture)



BOKEH 
Bokeh is the quality of out-of-focus or “blurry” parts of the image rendered by a camera lens – it is NOT the blur itself or the amount of blur in the foreground or the background of a subject. The blur that you are so used to seeing in photography that separates a subject from the background is the result of shallow “depth of field” and is generally simply called “background blur”. The quality and feel of the background/foreground blur and reflected points of light, however, is what photographers call Bokeh. Take a look at the following of BOKEH image:

Bad bokeh : Open up the larger version of the above image and see for yourself – the quality of the blur is not pleasant to the eye, with sharp edges of the circles and double lines.

Pay attention to the smooth background behind the child’s face. The out-of-focus areas look creamy and the circles are round and soft with beautiful transitions between the blurry areas. That’s exactly what you would call good bokeh!