Gdes 73 Terms
A barrier that opens and closes to control the amount of time the film or light sensor is exposed to light.
A thin opaque structure with an opening (aperture) at its centre. The role of the diaphragm is to stop the passage of light, except for the light passing through the aperture. Used to regulate the amount of light that enters the lens.
Sometimes used in leau of a shutter in digital cameras.
Analogous to an Iris.
|Iris||Most modern cameras use a type of adjustable diaphragm known as an iris diaphragm, and often referred to simply as an iris.|
Typical whole shutter speed scale:
The diameter of the opening in the diaphragm
A number derived from the focal length of the lens divided by the aperture diameter.
Used to set the aperture, which controls the size of the opening for light to pass through.
Each larger f stop number describes a smaller aperture that lets through 1/2 the light of the previous whole f stop.
Each smaller f stop number describes a bigger aperture that lets through 2 times the light of the previous whole f stop.
Typical whole fstop scale:
|Program/Auto Mode||The camera selects both the aperture and the shutter speed.|
|Shutter-Priority Mode||You set the shutter speed, and the camera sets the aperture.|
|Aperture-Priority Mode||You set the aperture, and the camera sets the shutter speed.|
|Manual Mode||You set the aperture and the shutter speed.|
A standard number used to rate Film Speed.
Also used to describe sensitivity of light sensors.
As ISO doubles, so does light sensitivity.
The image sensor.
No lens is perfect.
The subject is composed of small points at various distances.
Each point is small disc called circle of confusion.
When they are small enough, the eye sees them as points, and that part of the image will appear to be sharp (in the depth of field).
The larger the circles of confusion, the more likely an object will be out of focus. Points located in front or back of point have larger circles, and appear out of focus.(Depth of Field)
Longer focal lengths have larger relative aperture and resulting larger circles of confusion.The nearer you are to the subject, the more critical is the focus.
The distance from the point where the light makes its last bend after passing through the lens element (called the rear nodal point) to the point at which the light focuses perfectly onto the film(called the focal plane) when the lens is focussed at infinity.
Focal length effects magnification and angle of view
A longer lens has more magnification and less angle of view.
The shorter the focal length of the lens, the greater the depth of field
|Depth of Field||
The range of distance in front of and in back of the subject that objects still appear sharp.
More depth of field sometimes refered to as deeper depth of field.
Less depth of field sometimes refered to as a more shallow depth of field.
|Levels||A dialogue in Photoshop which allows you to adjust brightness and contrast.|
Increases the sensitivity of the image sensor.
Can result in noise(stray pixels of incorrect colors).
The amount of digital information used to store the color of a pixel
8 bits=256 colors
|angles of view||The amount of a scene that is visible in an image.|
|hyper focal distance||Setting a camera for maximum depth of field at a given f-stop.|
|zoom||A lens with variable focal lengths.|
A focal length longer than a normal lens.
Has less depth of field
Tends to flatten image(distances look compressed)
A focal length shorter than a normal lens.
Has more depth of field
Tends to distort image as focal length gets shorter.
|interpolation||Deriving pixels from nearby pixels.|
|RGB||Red, green and blue.|
|Resolution||The number of pixels per inch(example:72 dpi) or the number of total pixels on an image(example:3.5 megapixels)|
greyscale areas for color separations.
Complementary metal-oxide semiconductor
Alternative to CCD based cameras.