Patent ID: 7706682

Claim:
A wide-angle slip-on viewfinder for rangefinder cameras for analog and digital wide-angle recordings of different image recording formats with lenses of different focal lengths, comprising three lens groups, a frame/mask unit and a partially transmissive prism cube which comprises a combination element, wherein the first lens group arranged on the light entrance side in a viewfinder beam path has a negative refractive power and comprises two lenses of negative refractive power, wherein the first lens comprises a hollow meniscus with a convex surface arranged on the light entrance side and the second lens is a biconcave lens with an aspherical surface arranged on the light entrance side, the second and third lens groups have positive refractive power, wherein the second lens group comprises a first planoconvex lens, arranged downstream of the first lens group, with positive refractive power and a second biconvex lens with positive refractive power, the partially transmissive prism cube is arranged between the lenses and a planar surface of the first lens is cemented to the light-entrance-side surface of the partially transmissive prism cube, the third lens group is arranged in a mask imaging beam path which is at right angles to the viewfinder beam path between the frame/mask unit and the partially transmissive prism cube, a plurality of image field delimitation frames assigned to different lens focal lengths set by the frame/mask unit, wherein the image field delimitation frames have an outwardly curved shape which deviates from a rectangular shape of the image recording format for the compensation of distortions of the optical system of the third lens group and second lens of the second lens group, and the area ratio of a third to a first and smallest image field delimitation frame corresponds to the area ratio between an analog and digital image recording format.