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Biomedical subjects

K Knoblauch

Publications and source records attributed to K Knoblauch.

24 records · Page 2Linked to original sources
PubMed1987

On quantifying the bipolarity and axis of the Farnsworth-Munsell 100-Hue test.

A simple method is introduced for analyzing error score distributions from the Farnsworth-Munsell 100-Hue test. The method involves fitting a sine wave directly to the error distribution, and produces estimates of three parameters that characterize the severity of the defect, the degree of bipolarity, and the orientation of the axis of bipolarity, if one is present. The method produces good estimates of the orientation of the axes for congenital defects. It is also amenable to statistical analysis.

Color Perception Tests↗
PubMed1985

Linearity of hue cancellation in sex-linked dichromacy.

The results of several recent studies concur in the finding that for normal trichromats red-green hue-cancellation data obey linearity properties over rather general conditions, but for most observers yellow-blue hue-cancellation data do not. It is of interest to examine the question of cancellation linearity in sex-linked dichromats under the assumption that they represent reduced systems. We measured both the wavelength of the spectral achromatic point over a large range of intensities and yellow-blue hue-cancellation functions over the full spectrum and at several luminance levels in protanopes and deuteranopes. Both sets of data for the two types of dichromat satisfy linearity properties. These results are consistent with a model in which both cone receptor response functions have the same form. Implications for trichromatic opponent-response functions are considered.

Color Perception Tests↗
PubMed1978

Color vision testing: an alternative 'source' of Illuminant C.

The objective of this project was to evaluate an alternative procedure for administering reflective-type color vision tests. In this procedure, the tests are illuminated by a low color-temperature, 100 W, incandescent lamp (i.e. an improper illuminant) and the patient then views the illuminated test elements through an inexpensive gelatin filter placed before his eye (e.g. a Wratten 78AA costing about $4). Since the relative transmittance of this filter is quite similar to that used in the Macbeth Easel Lamp, the tests should still be valid. In fact, this alternative procedure yields test performances for normal and deficient subjects on the 100-hue, panel D-15, and AO H-R-R tests that are virtually identical to those obtained using a standard Macbeth Easel Lamp.

Color Perception Tests↗
PubMed1977

Validity of Pinckers' 100-Hue version of the Panel D-15.

Fifteen normal and 18 red-green-deficient subjects were tested with the Farnsworth Dichotomous Test of color vision (Panel D-15) and with an alternative version of the dichotomous test consisting of selected color chips from the Farnsworth-Munsell 100-Hue Test. Results indicate that the 100-Hue version of the dichotomous test is equivalent to the standard Panel D-15 with respect to detecting and differentiating among the more severe red-green deficiencies. These results confirm A. Pinckers' previous suggestion that the 100-Hue Test contains the components necessary for a Farnsworth Panel D-15.

Color Perception Tests↗
PubMedDate not supplied

Relating cone signals to color appearance: failure of monotonicity in yellow/blue.

Observers performed red-green and yellow-blue hue cancellation tasks for a 0.8-deg circular test field on a dark surround, by manipulating the excitation level of one cone class while the other two classes were held constant. The results of the red-green judgments conformed to classical opponent color theory in that both L- and S-cone excitation levels were antagonistic to M-cone signals. The yellow-blue judgments revealed a nonmonotonic nonlinearity in which the S-cone signal could act either antagonistically or synergistically with M- and L-cone signals. These results demonstrate that fixed hue sensations should not be associated with a given class of cone, even at the level of opponent neural coding.

Color Perception↗