IndexIntroductionDiscussionVisual perception and bottom-up processingContrast, contour, and colorMotion and sizeDesign caseDesign recommendationsConclusionReferencesIntroductionVisual perception is how we give a meaning to the world around us the light that enters our eyes. Throughout evolution, the act of processing signals and distinguishing them from surrounding noise has allowed humans to take necessary actions in response to environmental changes. These signals processed by the retina and visual cortex are vital aspects of cognition, because knowing how to distinguish between targeted signals and background noise is what allows humans to survive. This review examines theories and concepts focused on visual perception and analyzes the most important aspects for signal processing: contrast, color and size. When applied narrowly to user experience, these concepts have significant implications, as this understanding can distinguish a usable and effective interface from one that is not. By examining a real-world design example, Boston's iconic Citgo sign, we can begin to recognize how a critical understanding of visual perception, the biology of the human eye, and bottom-up design has major implications for the experience of user. plagiarism. Get a tailor-made essay on "Why Violent Video Games Shouldn't Be Banned"? Get an Original Essay Discussion Visual Perception and Bottom-Up Processing Visual perception is how humans process signals through visible light and its interaction with environmental stimuli. The act of picking up signals from our environment allows humans to take necessary precautions and actions in response to environmental changes. Although the nervous system is very good at recognizing and interpreting signals, these are not always clear. Signals are very often ambiguous, so determining the strength of the signal will allow better discrimination between a signal and noise. The stronger the signal, the easier it will be to process it compared to background noise. Bottom-up processing. The human eye, due to its numerous connections with the optic nerve, is very sensitive to signals. Light enters the eye through the cornea, then the lens focuses the light onto the photoreceptors (i.e. rods and cones) within the retina. Cones are “densely packed in the fovea” to help produce high resolution and color vision, while rods are located in the periphery of the retina to aid in the processing of light and motion under variable environmental conditions. Through a series of rapid eye movements, humans can process many signals simultaneously. With a single glance, the eye detects contrast, color, contour, motion, and size, all of which will be discussed in the following sections. Contrast, Contour and ColorContrast is one of the most important factors in determining the strength of a signal. Contrast is the degree to which a stimulus is different from other stimuli around it. Detects change between foreground and background. Just as our brain processes signals, the higher the contrast, the more the stimulus is perceived by the brain. In relation to design, it is critical to find a balance between maximum (strongest) contrast and threshold (weakest) contrast to produce the optimal signal. Over-designing or designing at the edge of barely noticeable differences (JND) is a fine balance and should be weighed heavily, as visual perception variesgreatly depending on the viewer and viewing conditions. Luminance and contour. Luminance is considered the most influential on contrast. Luminance is defined as the reflection or emission of visible light on a surface, and is also described as the measurement of perceived brightness (although luminance and brightness are not the same thing in practice). Due to the larger number of light-processing rods within the retina, humans are consequently more sensitive to luminance. This sensitivity to luminance allows humans to easily detect changes and adapt to a variety of lighting conditions. Over the course of evolution, humans have evolved to identify changes within the environment through improvements in contours (edges) or changes in luminance levels. Edges are created when the luminance of an object changes rapidly, creating a high contrast between the stimulus and its background. Once an edge is detected, nerves within the eye exaggerate and amplify it, allowing the visual cortex to process the object in our field of vision. This edge detection allows humans to recognize objects in our environment and assign them value and meaning based on appearance. Hue and saturation. Hues are how humans distinguish one spectral color from another in the visible light spectrum. Saturation, or purity of a hue, is the intensity of a hue at its dominant wavelength. When a hue is in its purest form, it is the most saturated and consequently has a great influence on the contrast and intensity of the signal. In contrast, an unsaturated hue would have “contributions from many other wavelengths” and much lower contrast. It is common practice to avoid using highly saturated hues in drawings, or at least use it sparingly, as pure hues can strain the eye due to strong contrast. In general, humans find pleasure and attractiveness in the most saturated hues, but it is important to keep in mind the disadvantages of using a hue with the highest saturation. Movement and Movement Size. Motion detection is one of the most important functions in visual perception, as it has a significant impact on sensitivity to contrast, depth and luminance. The human eye is very sensitive to movement, as it is processed and calculated by nerve endings located in the periphery of the retina. Movement “reflects a change in one's visual environment” and has a direct impact in understanding how real-world stimuli are formed and help with behavioral responses and actions. Since movement is by design, its overuse can cause overstimulation, since humans cannot block it. Designers should use change and movement deliberately and strategically to convey meaning. Dimensions. The size of a stimulus, along with luminance and contour, is equally important for signal processing. The size of a stimulus has a direct relationship with the signal. As the size of a stimulus increases, the strength of the signal also increases. Size can be heavily influenced by other influencing factors and complicating factors, such as viewing distance, viewing angle and environmental conditions. When comparing viewing distance and size, an inverse relationship exists; as the distance increases the perceived size appears smaller. In contrast, viewing angle and size have a direct relationship: as viewing angle increases, so does the size of the stimulus. Case designWhile each concept is relativeto signal processing has been described separately in the previous sections, in reality, they all affect one. each other. Through examining a real-world design case while observing the Citgo sign in Boston while driving at night, an analysis will be conducted to determine whether its design adheres to or runs counter to bottom-up visual perception. Luminance and edges. The sharp horizontal and vertical edges that form the signal boundaries are one of the first signals the driver will process. These abrupt changes in luminance along the edges add a stark contrast to the dark background, making only the mark more visible and the signal more intense. Likewise, the red triangle also has a strong contrast with the white background due to its shape and sharp edges. Because humans are neurologically tuned to detect contoured edges, nerves within the eye will amplify the edges both along the sides of the mark, and around the triangle, and strengthen the perceived contrast. At night, the luminance emitted by the LED lights inside the sign is incredibly intense, sending an equally strong signal to the visual cortex. With the Citgo sign located in the driver's field of vision while heading west on Storrow Drive, strong perceived brightness levels can be hazardous to driver safety. Especially in adverse weather conditions, the glare from bright lights can increase the likelihood of accidents, as the perceived brightness can temporarily blind the driver or cause "afterimages", which result in momentarily blurry and blurry vision. Since humans are generally more sensitive to changes in luminance, it is not surprising that looking at the Citgo sign while driving can interfere with drivers' safety. Saturation and hue. The LEDs inside the Citgo sign not only contain strong luminance contrast but also possess high saturation. The red and blue hues used in the Citgo logo have the greatest intensity, as both are at their dominant wavelength within the visible light spectrum. It is common practice to use saturation sparingly in interface design, as pure hues can strain the eye due to strong contrast. Red generally has good visibility due to the large number of red-sensitive cones within the fovea, but has poor visibility in low light conditions. The retina is less sensitive to blue than to red, but despite having only fewer blue-sensitive cones, the human eye tends to shift towards the blue end of the color spectrum at low levels of illumination, making it appear to have a higher luminance value. Although both red and blue are at two ends of the visible light spectrum, placing them close to each other, especially at full saturation, is a poor design decision. Red hues typically push towards the foreground of a stimulus and blue fades into the background. Because of this proximity, in addition to the strong luminance of the white background, the red and blue lights create a flickering effect, similar to movement at the periphery of the eye. While the Citgo sign already utilizes motion through several flashing, high-contrast patterns, the excess motion created by the saturated hues will only cause more distraction. Boston's Citgo sign can be seen from many parts of the city, as the large sixty-foot tall sign sits high above the buildings surrounding it. Because of the size and placement of the sign, motorists heading west on Storrow Drive have an especially good view of it. For a driver at night, the signal still stands outmore between the surrounding buildings, showing a strong contrast with the night sky and the buildings in its vicinity. No matter the viewing angle or distance, the contrast of the signal is so strong that even from a distance the signal sends a powerful signal to the driver. Especially when driving, this high contrast can prove incredibly dangerous, as the onset of these strong signals can quickly fatigue the sensory system due to rapid eye movement. LEDs with their higher amounts of luminance and saturation typically have much more abrupt activation times, compared to other light sources. Design Recommendations The Citgo sign's use of strong contrast, while achieving the goal of visibility, may present dangerous driving conditions for drivers, particularly at night. Creating such strong signals through the combination of intense luminance, large size, moving patterns, and highly saturated hues will eventually tire the sensory system. For interface designers, the overall goal of interaction design as it relates to visual perception is to find the optimal contrast. One suggestion is to use divided complement theory to reduce the saturation of the red and blue hues in the Citgo logo. Alternatively, mixing a few darker shades with your existing red and blue can also help reduce the intensity. Furthermore, reducing the luminance, especially at night, will reduce the strength of the signal sent to passers-by. This reduction can reduce perceived brightness and minimize glare caused by bright lights. Both of the suggested changes to contrast will allow for a more controlled and predictable result. Please note: this is just an example. Get a custom paper from our expert writers now. Get a Custom Essay Conclusion Visual perception is how humans understand and process our environment through the light that enters our eyes. By understanding signals and noise, the biology of the eye, and how visual contrast relates to the psychology and behavior of signal processing, designers will be able to apply these principles to exert greater control over user response to the design. Designers strive to produce predictable results, and the way to do this is to apply psychological and perceptual concepts related to signal strength and contrast. While each of these factors plays its own role in determining signal and contrast strength, it is important to know how the combination of these concepts impacts visual perception and design. Through examining the iconic Citgo sign in Boston, we can see how this combination of influencers can have a very strong and negative effect on the human eye. Understanding how each factor is at play will only make a designer more effective. By understanding how each factor is at play, designers should strive to reduce the burden we place on users by making designs even more effective and visually appealing. References Abdi, H. (1966). Signal_detection_theory[1].pdf (pp. 1–9). pp. 1–9.Albers, J. (1975). Color interaction (revised ed). Retrieved from http://www.amazon.co.uk/dp/0300018460Anderson, B. L. (2003). The role of occlusion in the perception of depth, lightness and opacity. Psychological Review, Vol. 110, pp. 785–801. https://doi.org/10.1037/0033-295X.110.4.785Aydin, T., Čadík, M., Myszkowski, K., & Seidel, H. P. (2010). Visually significant edges. ACM Transactions on Applied Perception, 7(4), 1–15. https://doi.org/10.1145/1823738.1823745 Brenner, E., & Van Damme, W. J. M. (1999). Perceived distance, shape and size. Research on, 1 (212), 69–76./10.1145/2072298.2071997