Optics and vision conscious sense organ, the eye allows vision. Rod and cone cells in the retina allow conscious light perception and vision including color differentiation and the perception of depth. The human eye can distinguish about 10 million colors. The human eye's non-image-forming photosensitive ganglion cells in the retina receive the light signals which affect adjustment of the size of the pupil, regulation and suppression of the hormone melatonin and entrainment of the body clock. Visual acuity is acuteness or clearness of vision, especially form vision, which is dependent on the sharpness of the retinal focus within the eye and the sensitivity
Kodak Retina Ausf. II Retina IIc, which is later mounted on the Type 019 Ausf. II Retina IB and Type 028 Retina IIIC. The second generation Type 034 Retina Reflex S of 1959 shared "S" type lenses with the Type 027 Retina IIIS (below), and offered fully coupled metering. With these the entire lens detached allowing for a wider range of focal lengths, 28mm to 200mm. At this point economical Japanese SLRs were becoming available and the Nikon F of 1959 would set the standard for future camera system. The Reflex III of 1961 and Reflex IV of 1964 brought minor improvements