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Contrast sensitivity is typically expressed as the reciprocal of the threshold contrast for detection of a given pattern (i.e., 1 ÷ contrast threshold). [15] Using the results of a contrast sensitivity exam, a contrast sensitivity curve can be plotted, with spatial frequency on the horizontal, and contrast threshold on the vertical axis.
Ordinary people have better reading performance using high-frequency (20–60 kHz) electronic ballasts than magnetic ballasts, [10] although the effect was small except at high contrast ratio. The flicker of fluorescent lamps, even with magnetic ballasts, is so rapid that it is unlikely to present a hazard to individuals with epilepsy . [ 11 ]
The contrast of each may be measured by inspection and recorded, giving a plot of attenuation vs. frequency. The NTSC3.58 multiburst pattern consists of 500 kHz, 1 MHz, 2 MHz, 3 MHz, and 3.58 MHz blocks. 3.58 MHz is important because it is the chrominance frequency for NTSC video.
Often the contrast reduction is of most interest and the translation of the pattern can be ignored. The relative contrast is given by the absolute value of the optical transfer function, a function commonly referred to as the modulation transfer function (MTF). Its values indicate how much of the object's contrast is captured in the image as a ...
Emits strong radio frequency electromagnetic radiation [45] None, although control circuitry may emit radio interference Size Up to 43 in (1.1 m) [46] Up to 120 in (3.0 m) [47] Up to 150 in (3.8 m) [48] (152 in experimental) [49] Up to 97 in (2.5 m) [50] Maintenance Hazardous to repair or service due to high-voltage,
[23] [24] The HDR display must have either a peak brightness of over 1000 cd/m 2 and a black level less than 0.05 cd/m 2 (a contrast ratio of at least 20,000:1) or a peak brightness of over 540 cd/m 2 and a black level less than 0.0005 cd/m 2 (a contrast ratio of at least 1,080,000:1).
The effect of the contrast transfer function can be seen in the alternating light and dark rings (Thon rings), which show the relation between contrast and spatial frequency. The contrast transfer function (CTF) mathematically describes how aberrations in a transmission electron microscope (TEM) modify the image of a sample.
The "luminance contrast" is the ratio between the higher luminance, L H, and the lower luminance, L L, that define the feature to be detected.This ratio, often called contrast ratio, CR, (actually being a luminance ratio), is often used for high luminances and for specification of the contrast of electronic visual display devices.