threshold contrast

threshold contrast

[′thresh‚hōld ¦kän‚trast]
(optics)
The smallest contrast of luminance (or brightness) that is perceptible to the human eye under specified conditions of adaptation luminance and target visual angle. Also known as contrast sensitivity; contrast threshold; liminal contrast.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
The Digit/Character Recognition Test measured the threshold contrast for each sized single digit.
Table 2 and Figures 5 to 9 present CSF, threshold contrast, and Barten SQRI results.
In comparison, a further analysis was done with the participants' best digit contrast sensitivity (at whatever size character was their individual best performance in threshold contrast sensitivity, which was always [greater than or equal to] 2[degrees]) (Figure 8).
Russian astronomer Vsevolod Sharonov, a pioneer in the field of planetary photometry, pointed out that reducing the difference in brightness between the disk of a planet and the background against which it is seen significantly improves the threshold contrast sensitivity of the eye.
With the threshold contrast set to 5% (CIE, 1987), this definition yields the following expression:
The threshold Contrast sensitivity function in strabismic amblyopia: Evidence for a two type classification.
ODM uses Clark's formulas to calculate a threshold contrast at which objects become visible, based on several parameters defined by the user: sky brightness, aperture, object brightness, and object size.
Log Object Contrast: +0.15 Log Threshold Contrast: -0.08 Log Contrast Difference: +0.23 ODM: 55X While for the urban setting,
Log Object Contrast: -1.45 Log Threshold Contrast: -0.82 Log Contrast Difference: -0.63 ODM: Not detectable Not surprisingly, ODM predicts the galaxy will not be visible in the urban environment.
How can light-polluted skies lower the threshold contrast? I believe this is caused by the eye's performance being closer to photopic (daytime vision) in a brightly lit urban environment.
Log Object Contrast: -1.45 Log Threshold Contrast: -1.42 Log Contrast Difference: -0.03 ODM: Not detectable If aperture is the equal of dark skies, then the 40-inch--with its 44-times advantage in light-gathering power--should perform just as well as the smaller scope--with its 4-magnitude (40-times) advantage in sky darkness.
One insight has been the realization that, as aperture increases, the threshold contrast at which galaxies emerge from the dark of night decreases.