Perceiving color across scale: great and small, discrete and continuous.

We generalize, to images with continuously varying colors, our previously published model for comparing color differences of spatially discrete visual fields (icons, symbols) of disparate sizes. Our model is structural, including scattering of light by the intraocular media, followed by sparse retinal cone cell sampling of each physiological color primary. We use our model to show that small subtense of less than half a degree drastically reduces the number of discriminable colors available within a color gamut. The proposed generalization predicts and explains appearance of color fields having a wide range of subtenses (from 1/8 deg to 44 deg in examples given).

Observer performance using virtual pathology slides: impact of LCD color reproduction accuracy.

The use of color LCDs in medical imaging is growing as more clinical specialties use digital images as a resource in diagnosis and treatment decisions. Telemedicine applications such as telepathology, teledermatology, and teleophthalmology rely heavily on color images. However, standard methods for calibrating, characterizing, and profiling color displays do not exist, resulting in inconsistent presentation. To address this, we developed a calibration, characterization, and profiling protocol for color-critical medical imaging applications. Physical characterization of displays calibrated with and without the protocol revealed high color reproduction accuracy with the protocol. The present study assessed the impact of this protocol on observer performance. A set of 250 breast biopsy virtual slide regions of interest (half malignant, half benign) were shown to six pathologists, once using the calibration protocol and once using the same display in its "native" off-the-shelf uncalibrated state. Diagnostic accuracy and time to render a decision were measured. In terms of ROC performance, Az (area under the curve) calibrated = 0.8570 and Az uncalibrated = 0.8488. No statistically significant difference (p = 0.4112) was observed. In terms of interpretation speed, mean calibrated = 4.895 s; mean uncalibrated = 6.304 s which is statistically significant (p = 0.0460). Early results suggest a slight advantage diagnostically for a properly calibrated and color-managed display and a significant potential advantage in terms of improved workflow. Future work should be conducted using different types of color images that may be more dependent on accurate color rendering and a wider range of LCDs with varying characteristics.