Rapid fixer is a fixing solution that uses ammonium thiocyanate or thiosulfate instead of hypo. Rapid rectilinear is a lens system composed of two matching doublet lenses, symmetrically placed around the focal aperture. It was introduced by Dallmeyer and Sternheil and removed many of the aberrations present in more simple constructions. Rear curtain sync is when the flash fires an instant before the second or rear curtain of the focal plane shutter begins to move. When slow shutter speeds are used, this feature can create a blur effect from the ambient light, i.e., patterns following a moving subject with subject movement frozen at the end.
Rear focus refers to the focused area behind the picture's subject.
Rear focusing system is a system where only the rear lens group moves during focusing. It eliminates changes in the physical length of the lens during focusing. Rebate is the margin on photographic film surrounding the image area. Reciprocity failure in photographic emulsions occurs when exposure times fall outside a films normal range. At these times an increase in exposure is required in addition to the assessed amount.