The old 8-bit industry standard has become 16 and even 24 bits. A series of frames is taken, and then the images are compiled to increase the total image content of each pixel. This requires a very stable image and camera to prevent blurring. In this way, long exposures of very dim images can be taken without risk of saturation and blooming. A video rate camera and framegrabber are usually necessary for this operation.
Optics play an important role in image quality.
The degree of diffraction and light scattering affects the ability to distinguish close points in the image. For low-end applications such as most electrophoretic imaging, this is of minimal concern. CCDs are rated in terms of their defect content on a scale from zero to three, zero being the highest quality. The major categories are point, cluster, column, hot, and charge type defects. A point defect occurs when a single pixel has a response profile that differs from that of its neighbors.