Sensation is the process by which sensory receptors transduce physical stimulation in the environment into neural impulses: photoreceptor pickup of light. Perception is the process by which sensory input is interpreted to form a meaningful subjective percept. Contralateral organization: stimuli on left side are projected to right side of brain, vice versa. Early studies on brain laterally looked at processing differences between left and right hemispheres by presenting stimuli either in right or left visual fields. Although primary visual cortex receives bulk of visual input, subcortical pathways in the thalamus also receive input. The scientific study of how our subjective percept is related to the physical properties of environmental stimuli. Increase in stimulus intensity needed to perceive a change in intensity is proportional to origin al stimulus intensity. Contrast is the difference in luminance between adjacent elements of a scene. Orientation refers to direction information contained within an image.