A Comparison of Photographic and Photoelectric Measurements of Atmospheric Attenuation of Brightness Contrast*

1949 ◽  
Vol 39 (12) ◽  
pp. 990 ◽  
Author(s):  
Howard S. Coleman ◽  
Harold E. Rosenberger
Keyword(s):  
Brightness Contrast ◽  
Atmospheric Attenuation ◽  
Photoelectric Measurements

Cosmetology treatments on human hair: An SEM study

1996 ◽  
Vol 54 ◽  
pp. 940-941
Author(s):  
D.F. Bowling
Keyword(s):  
High School ◽  
High Resolution ◽  
Human Hair ◽  
Optical Microscope ◽  
Convincing Evidence ◽  
Brightness Contrast ◽  
Sem Study

High school cosmetology students study the methods and effects of various human hair treatments, including permanents, straightening, conditioning, coloring and cutting. Although they are provided with textbook examples of overtreatment and numerous hair disorders and diseases, a view of an individual hair at the high resolution offered by an SEM provides convincing evidence of the hair‘s altered structure. Magnifications up to 2000X provide dramatic differences in perspective. A good quality classroom optical microscope can be very informative at lower resolutions.Students in a cosmetology class are initially split into two groups. One group is taught basic controls on the SEM (focus, magnification, brightness, contrast, specimen X, Y, and Z axis movements). A healthy, untreated piece of hair is initially examined on the SEM The second group cements a piece of their own hair on a stub. The samples are dryed quickly using heat or vacuum while the groups trade places and activities.

scholarly journals Asteroid Polarimetry: A Progress Report

1971 ◽  
Vol 12 ◽  
pp. 91-94
Author(s):  
J. Veverka
Keyword(s):  
Present Status ◽  
Progress Report ◽  
Polarization Curves ◽  
Photographic Method ◽  
Polarization Measurements ◽  
Partial Data ◽  
Low Sensitivity ◽  
Photoelectric Measurements

This is a brief report on the present status of asteroid polarimetry. A detailed paper is in preparation jointly with T. Gehrels.The first polarization measurements of asteroids were made by Lyot (1934), who photographically determined the polarization curves of Ceres and Vesta. These curves are reproduced by Dollfus (1961). Unfortunately, because of the low sensitivity of the photographic method, they do not agree very well with recent photoelectric measurements.The first photoelectric polarization measurements of asteroids were made by Provin (1955) (details of this work are given by Dollfus, 1961), and in recent years this work has been extended by Gehrels (unpublished) and by Veverka (1970). To date, fairly complete polarization curves for about a dozen asteroids have been obtained, and at least partial data are available for twice that number.

Illusory Reversal of Brightness Contrast

1968 ◽  
Vol 27 (3_suppl) ◽  
pp. 1169-1170 ◽  
Author(s):  
Whitman Richards
Keyword(s):  
Visual System ◽  
Visual Angle ◽  
Low Frequency ◽  
Brightness Contrast ◽  
Linear Behavior ◽  
Non Linear

An illusion analogous to Cornsweet's is used to demonstrate how the non-linear behavior of the visual system can be used to obscure low-frequency gradients. The result is a reversal of brightness—from light to dark—as the visual angle of the display is changed.

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