Zoom finder

A zoom finder including an objective optical system of a positive power having a first lens group of negative power, a second lens group of positive power and a third lens group, and an eyepiece optical system of positive power through which an image formed by said objective optical systme is observed, comprising:

• power-varying means for moving said second lens group along the optical axis of said objective optical system to vary the power;
• diopter-adjusting means for moving said first lens group in association with said second lens group in order to maintain a constant diopter;
• and
• means for producing a field flattening effect with said third lens group for correcting a curvature of field,
• wherein a focal length f3 of said third lens group and a focal length f.sub.t of said objective optical system satisfy .vertline.f.sub.T /f3.vertline.<0.5 at a telephoto extremity.

A zoom finder, including at least one movable lens group, said zoom finder comprising:

• an objective optical system of positive power having a first lens group of negative power, a second lens group of positive power, and means for producing a field flattening effect for correcting a curvature of field;
• and
• an eyepiece optical system of positive power through which an image formed by said objective optical system is observed
• said means for producing a field flattening effect comprising a third lens group and wherein a focal length f3 of said third lens group and a focal length f.sub.T of said objective optical system at a telephoto extremity satisfy the following relationship:
• .vertline.f.sub.T /f3/<0.5.