The viewfinder in this camera was designed for the standard lens which is the focal lengths of 35mm. So, in case you use other lenses, you have to prepare the supplementary viewfinders for them and attach it to the accessory shoe (where the yellow-colored arrow points in the picture).
Available lenses for this camera are as follows:

• Standard lens; Tricor F2.7/35mm, F3.5/35mm, Wollensak Univex-Hexar F2/35mm
• Tele lens; 75mm, 125mm

Lens mounts of all them are screw-in mount.