B&W Black and white.
(Bulb) - letter on the shutter dial indicating that the shutter will stay open while the release is depressed.
Back focus - distance between the back surface of the lens and the image plane, when the lens is focused at infinity. Background - area shown behind the main subject in a picture. ....Lets read more
Abbe number - denotes the degree of refraction of light of different wavelengths to different extents, given by a transparent material, such as glass. The lower the Abbe number, the greater the dispersion of colors.
Aberration - the inability of a lens to produce a perfect, sharp image, especially towards the edge of the lens field. These faults can be reduced by compound lens constructions, and the use of small apertures.
Abrasion marks - marks on the emulsion surface of a film, caused by scratching. It can be due to traces of dirt trapped between layers of film as it is wound on the spool, or to grit on the pressure plate. ....Lets read more
