These specialized cells are called photoreceptors. Rods are sensitive to light levels and cones are sensitive to colour. The cones secrete the pigment iodopsin and are most effective in bright light. The rods, which secrete a substance called visual purple, or rhodopsin, provide vision in dim light or semidarkness. Thus cones need high light levels to get activated and rods need low light levels to be activated.
Cones are more near the centre of the retina.
Rods are more near the periphery of the retina. But after a short while you can see . Of course you will never be able to see in complete darkness. There has to be some trace of light in a room for you to see in the dark. When you first enter a dimly lit room, the cones in your retina are in an activated state.