Valonhankinta

Valonhankinta, literally "light acquisition" in Finnish, refers to the process by which an imaging system or a biological photoreceptor gathers photons from a scene to generate a measurable signal. In photography and digital imaging, valonhankinta encompasses the optical path, sensor characteristics, and exposure settings that determine how much light is collected and how it is converted into an electrical signal.

The main factors that influence valonhankinta are the optics, including aperture size, lens transmittance, and any filters; the sensor properties, such as pixel size, fill factor, quantum efficiency, and readout noise; and the exposure control, including shutter speed, exposure value, and sensor gain. The illumination of the scene and its dynamic range also play a critical role, as brighter scenes allow more light to be captured quickly, while dim scenes require longer exposure or higher sensitivity.

In practice, valonhankinta involves balancing brightness, noise, and motion. Underexposure leads to dark images with high noise or loss of detail in shadows, whereas overexposure causes highlight clipping and loss of detail in bright regions. In scientific imaging, accurate valonhankinta is essential for quantitative measurements and is often followed by calibration and radiometric correction to convert pixel values to physical units such as radiance or irradiance.

In vision science, valonhankinta also describes the initial transduction of light by photoreceptors, where photons are converted into neural signals and integrated over time according to the organism’s spectral sensitivity.

Related concepts include exposure, radiometry, imaging sensor, and photodetection.