ABSTRACT
The camera viewfinder has progressed from a simple means of aiming the camera to a complex optical or opto-electronic device incorporating several major functions. The viewfinder aids composing, which is a matter of aesthetic and artistic consideration. The aspect ratio may dominate the picture as previewed, which is a criticism of some formats. The properties of human vision and its physiological disadvantages must be considered in viewfinder design. Retinal sensitivity to light varies and can be many thousand times greater in low light levels than in daylight. This increase is called dark adaptation, and is a slow process, requiring about 30 minutes to reach maximum. A viewfinder using the camera lens may be considered to be highly corrected in terms of image quality. Another form of interactive viewfinder is where an eyepiece attachment is used containing relay optics and a small video sensor system to convey the view-finder image to a remote observer for viewing on a monitor screen.
