Photoreceptor cell cell depends upon only the number of photons absorbed. The different responses of the three types of cone cells are determined by the likelihoods that their respective photoreceptor proteins will absorb photons of different wavelengths. So, for example, an L cone cell contains a photoreceptor protein that more readily absorbs long wavelengths of light (i.e., more "red"). Light of a shorter wavelength can also produce the same response, but it must be much brighter to do so. The human retina contains about 120 million rod cells, and 6 million cone cells. The number and ratio of rods to cones varies
Kodak Retina Reflex is coupled to the aperture ring - moving the shutter ring automatically moves the aperture ring, so that the same exposure value is maintained. In other words, when in use, the camera is normally locked into one EV setting until the aperture release tab is pressed. Needless to say this can be confusing to those unfamiliar with the camera. All the Retina Reflex cameras are remarkably complex instruments and quite heavy for their size. The Retina Reflex originally sold for $215 USD (app. $1,820 USD in 2014). Approximately 65,000 were made. The Retina Reflex can be fitted with four different