Midterm Flashcards
Define bit
0 or 1 (binary digit)
define byte
8 bits or one word
normal display amount of bits
8 bit = 2^8= 256
true color
8 bits per color or 256 ^3
what is a digital image made of
pixels arranged in rows and columns on a matrix defined by its height and width
explain sampling and quantization
sampling is essentially the number of pixels while quantization is the value given to the pixels
nyquist theorem
Must sample at twice the highest frequency present in subject to visualize
in digital imaging how is sampling frequency determined
by pixel size and spacing (resolution)
Theoretical vs actual resolutions
MTF (modulation transfer function) yields actual resolutions of 1/2 to 3/4 of theoretical
causes of noise
Sensor related: Pixel cross-talk, Dark current, Excessive gain
System related: Scatter radiation, Collimation, Photon output
dynamic range
the largest possible signal divided by the smallest possible signal it can generate. The largest possible signal is directly proportional to the full well capacity of the pixel. The lowest signal is the noise level when the sensor is not exposed to any light, also called the “noise floor”.
types of image enhancements
spatial domain (point and group) and frequency domain
what does spatial frequency measure
how rapidly parts of the image change brightness
loss pass filter, smooths high frequency areas (softens the abrupt changes in brightness)
adds together the adjacent boxes and multiplies by the inverse of the number of boxes (ie for a 3 x 3 boxcar, add all up and multiply by 1/9)
high pass filter
sharpens image, removes low frequencies
