kontrastfølsomhetsfunksjon

A kontrastfølsomhetsfunksjon, often abbreviated as CSF, is a psychophysical measurement that describes a person's ability to detect differences in luminance, or contrast, across a range of spatial frequencies. In simpler terms, it quantifies how well someone can see details of varying sizes, from broad shapes to fine textures. The CSF is typically plotted as a graph with spatial frequency on the x-axis and the minimum detectable contrast (or sensitivity) on the y-axis.

The shape of the CSF is generally bell-shaped. At very low spatial frequencies (large objects), a relatively low contrast is needed for detection. As spatial frequency increases (objects become smaller and finer), the required contrast rises, meaning sensitivity decreases. This is the decreasing limb of the curve. Beyond a certain point, at very high spatial frequencies (extremely fine details), detection becomes impossible even at maximum contrast. This represents the high-frequency cut-off. The peak sensitivity usually occurs at intermediate spatial frequencies.

Factors influencing the CSF include age, visual pathology (such as glaucoma or cataracts), lighting conditions, and the presence of chromatic aberrations. Measuring the CSF is a valuable tool in ophthalmology and optometry for diagnosing and monitoring visual impairments, as changes in CSF can indicate underlying visual system dysfunction. It provides a more comprehensive assessment of visual function than simple visual acuity measurements, which primarily assess the ability to resolve high-contrast details at a specific size.