focal-plane shutter

The high speeds of the focal-plane shutter incorporated into such a camera will rarely be utilised by the average user; but its other features are admirable.

For the 3 1/4 x 4 1/4:   One lens 4 or 4 1/2 focus   One lens 6 or 7 focus   One lens telephoto or telecentric 9 to 12 focus The camera should be made of metal and fitted with focal-plane shutter and direct view-finder.