Spatial Integration of Objectively Equiluminous Chromatic Gratings

Perception ◽  
1997 ◽  
Vol 26 (1_suppl) ◽  
pp. 200-200
Author(s):  
M I Kankaanpää ◽  
J Rovamo ◽  
H T Kukkonen ◽  
J Hallikainen
Keyword(s):  
Spatial Frequency ◽  
Contrast Sensitivity ◽  
Spatial Integration ◽  
Chromatic Contrast ◽  
Shape Difference ◽  
Sensitivity Functions ◽  
Spatial Frequencies ◽  
Low Pass ◽  
Chromatic Aberrations ◽  
Chromatic Contrast Sensitivity

Contrast sensitivity functions for achromatic and chromatic gratings tend to be band-pass and low-pass in shape, respectively. Our aim was to test whether spatial integration contributes to the shape difference found at low spatial frequencies. We measured binocular chromatic contrast sensitivity as a function of grating area for objectively equiluminous red - green and blue - yellow chromatic gratings. Chromatic contrast refers to the Michelson contrast of either of the two chromatic component gratings presented in counterphase against the combined background. Grating area ( A) varied from 1 to 256 square cycles ( Af2) at spatial frequencies ( f) of 0.125 – 4.0 cycles deg−1. We used only horizontal gratings at low and medium spatial frequencies to minimise the transverse and longitudinal chromatic aberrations due to ocular optics. At all spatial frequencies studied, chromatic contrast sensitivity increased with grating area. Ac was found to be constant at low spatial frequencies (0.125 – 0.5 cycles deg−1) but decreased in inverse proportion to increasing spatial frequency at 1 – 4 cycles deg−1. Thus, spatial integration depends similarly on spatial frequency for achromatic (Luntinen et al, 1995 Vision Research35 2339 – 2346) and chromatic gratings, and differences in spatial integration do not contribute to the shape difference of the respective contrast sensitivity functions.

Investigation of Chromatic Contrast Sensitivity Based on Different Color Directions and Spatial Frequencies

2011 ◽  
Vol 31 (1) ◽  
pp. 0133002 ◽  
Author(s):  
吕玮阁 Lü Weige ◽  
徐海松 Xu Haisong ◽  
汪哲弘 Wang Zhehong ◽  
M. Ronnier Luo M. Ronnier Luo
Keyword(s):  
Contrast Sensitivity ◽  
Chromatic Contrast ◽  
Spatial Frequencies ◽  
Different Color ◽  
Chromatic Contrast Sensitivity

scholarly journals Are Spatial Chromatic Contrast Sensitivity Band-pass or Lowpass Functions?

2020 ◽  
Vol 2020 (28) ◽  
pp. 125-129
Author(s):  
Qiang Xu ◽  
Stephen Westland ◽  
Marcel Lucassen ◽  
Dragan Sekulovski ◽  
Sophie Wuerger ◽  
...  
Keyword(s):  
Contrast Sensitivity ◽  
Threshold Method ◽  
Colour Difference ◽  
Chromatic Contrast ◽  
Experimental Conditions ◽  
Colour Centres ◽  
Spatial Frequencies ◽  
Wide Range ◽  
Band Pass ◽  
Chromatic Contrast Sensitivity

The goal of this research is to generate high quality chromatic Contrast Sensitivity Function (CSF) over a wide range of spatial frequencies from 0.06 to 3.84 cycles per degree (cpd) surrounding 5 CIE proposed colour centres (white, red, yellow, green and blue) to study colour difference. At each centre, 6 colour directions at each of 7 frequencies were sampled, from 0.06 to 3.84 cycles per degree (cpd) corresponding to the number of cycles: from 2.3 to 144.4 respectively. A threshold method based on forced-choice stair-case was adopted to investigate the just noticeable (threshold) colour difference. The results revealed that the chromatic CSF under the present experimental conditions having many lower spatial frequencies covering five colour centres to be band pass, whereas previous results indicated it was low pass. However, this could be caused by the present experimental conditions such as fixed-size stimuli and constant luminance. The new chromatic CSF for R-G and Y-B channels were also developed.

A Comparative Study of the Spatial-Frequency Spectrum of Different Letter Optotypes and its Role in Target Recognition

Perception ◽  
1997 ◽  
Vol 26 (1_suppl) ◽  
pp. 214-214 ◽  
Author(s):  
S A Koskin ◽  
V F Danilichev ◽  
Y E Shelepin
Keyword(s):  
Spatial Frequency ◽  
Contrast Sensitivity ◽  
Frequency Spectrum ◽  
Brain Diseases ◽  
Sinusoidal Grating ◽  
Sensitivity Functions ◽  
Spatial Frequencies ◽  
Wide Range ◽  
Narrow Frequency Band ◽  
Spatial Frequency Spectrum

We studied the contrast sensitivity functions (CSFs) in patients with different eye and brain diseases using a computerised sinusoidal grating test with a wide range of frequencies (0.4 – 19.0 cycles deg−1), the Pelli - Robson chart and a new chart with frequency-filtered Snellen optotypes. The patients had different CSF curves with a decrease of contrast sensitivity in the low, middle, or high frequencies depending on their main disease (refraction anomalies, cataract, glaucoma, neuritis of optic nerve, brain tumours, etc). Analysis showed that optotypes in the Pelli - Robson chart have a wide-range spatial-frequency spectrum, and optotype recognition is determined not only by low spatial frequencies. We find that the recognition of standard Sloan's optotypes is determined mostly by sensitivity in the range of 9.4 – 14.0 cycles deg−1. At the same time we measured contrast sensitivity using the new filtered Snellen optotypes. Our calculations support our earlier suggestions that the new filtered optotypes have a narrow-band spatial-frequency spectrum, thus enabling selective measurement of contrast sensitivity in each narrow frequency band.

Acuity and contrast sensitivity of the bluegill sunfish and how they change during optic nerve regeneration

2007 ◽  
Vol 24 (3) ◽  
pp. 319-331 ◽  
Author(s):  
D.P.M. NORTHMORE ◽  
D.-J. OH ◽  
M.A. CELENZA
Keyword(s):  
Optic Nerve ◽  
Spatial Frequency ◽  
Contrast Sensitivity ◽  
Cutoff Frequency ◽  
Lepomis Macrochirus ◽  
High Spatial Frequency ◽  
Contrast Threshold ◽  
Bluegill Sunfish ◽  
Sensitivity Functions ◽  
Spatial Frequencies

Spatial vision was studied in the bluegill sunfish, Lepomis macrochirus (9.5–14 cm standard length) to assess the limitations imposed by the optics of the eye, the retinal receptor spacing and the retinotectal projection during regeneration. Examination of images formed by the dioptric elements of the eye showed that spatial frequencies up to 29 c/° could be imaged on the retina. Cone spacing was measured in the retina of fresh, intact eyes. The spacing of rows of double cones predicted 3.4 c/° as the cutoff spatial frequency; the spacing between rows of single and double cones predicted 6.7 c/°. Contrast sensitivity functions were obtained psychophysically in normals and fish with one regenerating optic nerve. Fish were trained to orient to gratings (mean luminance = 25 cd/m2) presented to either eye. In normals, contrast sensitivity functions were similar in shape and bandwidth to those of other species, peaking at 0.4 c/° with a minimum contrast threshold of 0.03 and a cutoff at about 5 c/°, which was within the range predicted by cone spacing. Given that the optical cutoff frequency exceeds that predicted by cone spacing, it is possible that gratings could be detected by aliasing with the bluegill's regular cone mosaic. However, tests with high contrast gratings up to 15 c/° found no evidence of such detection. After crushing one optic nerve in three trained sunfish, recovery of visual avoidance, dorsal light reflex and orienting to gratings, were monitored over 315 days. At 64–69 days postcrush, responses to gratings reappeared, and within 2–5 days contrast sensitivity at low (0.15 c/°) and medium (1.0 c/°) spatial frequencies had returned to normal. At a high spatial frequency (2.93 c/°) recovery was much slower, and complete only in one fish.

Modeling chromatic contrast sensitivity across different background colors and luminance

2021 ◽  
Vol 2021 (29) ◽  
pp. 99-104
Author(s):  
Marcel Lucassen ◽  
Dragan Sekulovski ◽  
Marc Lambooij ◽  
Qiang Xu ◽  
Ronnier Luo
Keyword(s):  
Spatial Frequency ◽  
Contrast Sensitivity ◽  
Constant Stimulus ◽  
Stimulus Size ◽  
Experimental Paradigm ◽  
Chromatic Contrast ◽  
Data Set ◽  
Contrast Model ◽  
Model Based ◽  
Chromatic Contrast Sensitivity

In this research we compare chromatic contrast sensitivity models for two separate datasets and for the pooled dataset. They were obtained from two studies employing a very similar experimental paradigm. The data represent threshold visibilities of chromatic Gabor patterns varying in spatial frequency, background chromaticity, direction of color modulation and luminance, at constant stimulus size. Using the extended data set, we reconfirm our previously reported finding that a model based on coloropponent contrast signals is an improvement over a cone contrast model. However, when linear background scaling in classic cone contrast is replaced by nonlinear background scaling, an improvement of almost similar size is obtained. The results of this study can be of interest for the development of vision models employing the processing of spatio-chromatic information.

scholarly journals Are Contrast Sensitivity Functions Impaired in Insulin Dependent Diabetics Without Diabetic Retinopathy?

1999 ◽  
Vol 42 (4) ◽  
pp. 133-138 ◽  
Author(s):  
Vladimír Liška ◽  
Miroslav Dostálek
Keyword(s):  
Visual Acuity ◽  
Diabetic Retinopathy ◽  
Spatial Frequency ◽  
Contrast Sensitivity ◽  
Dependent Diabetes Mellitus ◽  
Control Group ◽  
Study Group ◽  
Sensitivity Functions ◽  
Spatial Frequencies ◽  
Insulin Dependent

Purpose: To confirm the influence of multilevel metabolic disturbance of insulin dependent diabetes mellitus (IDDM) on the vision even before the onset of the other changes routinely evaluated by ophthalmologists. Methods: Contrast sensitivity functions (CSFs) were estimated using the VCTS 6500 board. The standardised measurement procedure was performed. The value of the threshold contrast sensitivity was obtained for five spatial frequencies (1.5 - 3 - 6 - 12 - 18 c/deg). Other data was collected (duration of diabetes, BCVA, funduscopy, fluoresceine angiography, HbA1C). The study group consisted of 48 IDDM patients (94 eyes) without diabetic retinopathy and with Snellen BCVA > 1.0. The control group (56 normals, 98 eyes) was age and BCVA matched. Results: Highly statistically significant decrease of the CSFs in all spatial frequencies in the study group was obtained. Correlation between duration of the diabetes and impaired degree of CSFs was present in the middle spatial frequency. No significant changes in CSFs were found among patients with pathological value of glycated hemoglobin HbA1c (>7.8 %). Conclusions: If compared with routinely used Snellen visual acuity, the CSFs are more complex descriptors of the subjects vision abilities. IDDM has an influence on these sensitive functions, especially during examination in the middle spatial frequency of 6 and 12 c/deg, before disturbing visual acuity and before changes in the retinal morphology. Decrease of CSFs was influenced mainly by the patients’ age and partially (in the middle spatial frequency) by the IDDM duration.

Measurement of CIELAB spatio-chromatic contrast sensitivity in different spatial and chromatic directions

2019 ◽  
Vol 2019 (1) ◽  
pp. 326-330
Author(s):  
Vlado Kitanovski ◽  
Alastair Reed ◽  
Kristyn Falkenstern ◽  
Marius Pedersen
Keyword(s):  
Contrast Sensitivity ◽  
Low Frequency ◽  
Published Data ◽  
Psychophysical Experiment ◽  
Frequency Range ◽  
Chromatic Contrast ◽  
Vertical Orientation ◽  
Spatial Frequencies ◽  
The Impact ◽  
Chromatic Contrast Sensitivity

This paper presents data on CIELAB chromatic contrast sensitivity collected in a psychophysical experiment. To complement previously published data in the low-frequency range, we selected five spatial frequencies in the range from 2.4 to 19.1 cycles per degree (cpd). A Gabor stimulus was modulated along six chromatic directions in the a*-b* plane. We also investigated the impact on contrast sensitivity from spatial orientations – both vertically and diagonally oriented stimuli were used. The analysis of the collected data showed lowest contrast sensitivity in the chromatic direction of around 120° from the positive a*-axis. The contrast sensitivity in the diagonal spatial orientation is slightly lower when compared to the vertical orientation.

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