2 Previous Work

Acquiring satisfactory and usable images with a camera involves ensuring that the film or digital sensor in a camera is properly exposed given a scene’s illumination strength and color. Several camera parameters affect this process. To properly handle variations of lighting strength a camera’s exposure can be adjusted by varying three parameters: exposure time, aperture size, and film or sensor sensitivity (ISO). To properly color balance a photo, the lighting color needs to be offset by adjusting the camera white-balance. This white-balance setting affects the relative ratio of red, green, and blue so that photos can be captured that better reflect the human perception of an object’s color under varied lighting color. Each exposure adjustment has its own tradeoff that can lead to various image artifacts in low-light conditions. Long exposure times allow more light to be captured, but increase the chances of getting blurred images if an object or the camera moves during the exposure window. Large apertures allow more light to reach the film or sensor, but can cause depth-dependent blur as the depth of field is decreased. High ISOs increase image contrast; however, they increase image noise – for film cameras, larger ISOs correspond to larger film grain, thus noise appears as the large discrete film grains become visible, while for digital cameras, ISO represents a gain that amplifies sensor noise in addition to the image signal. As a result, acquiring high-quality images in low-light conditions can be quite challenging.