Contrast is a sensory trait that makes stimuli stand out. Writers, designers and musicians all use contrast to emphasize striking differences in text, visual displays and melodies. In the vision, the brightness contrast describes the difference in light intensity between a stimulus and its environment.
This is what makes a dark letter easier to read than a gray letter on a white page. Vision research has been under the assumption for decades that the brightness contrast does not change with light intensity. That is, a dark letter in a white page outside the contrast (under the brightest light) as indoors (under the darkest light) has the same contrast. Of course, such contrast resistance seems to be important. How can it be otherwise? If contrast were not maintained over different light intensities, a black letter would turn white indoors because it reflects much more light.
New York University College of Optometry researcher Hamed Rahimi-Nasrabadi, PhD, and associates now point out that these decades-old assumptions are wrong and can cause important measurement errors that have general implications for basic research, the eye clinic and the multiple disciplines depend on accurate estimates of the visual contrast.
This could lead, for example, to inaccurate measurements of visual sensitivity in eye diseases, the rendering of contrast in medical images or the architectural design of spaces for the visually impaired and the elderly.
The new findings show that counter-sensitivity, depending on the sharpness, is strongly dependent on the amount of light. As you increase the amount of light, the contrast sensitivity to dark and light stimuli (ie stimuli darker or lighter than their surroundings) shifts in opposite directions. It improves the discrimination of the darkest contrasts (makes it easier to see subtle differences in the eye shadow), while seriously undermining the discrimination of the brightest contrasts (eg makes it harder to see the brightness differences between the brightest mirror reflections of a shiny car to distinguish).
The opposite shifts of dark and light contrast with the light intensity can be shown in neurons of the visual cortex, natural scenes, and it seems to be well preserved in different species of mammals. The new findings can also be used to improve the current algorithms of image processing and visual contrast criteria.
The findings from the investigation conclude that you can now feel good if you decide to read your favorite book outdoors. You can say that it has been scientifically proven that the visual contrast in the outdoors increases, and therefore under bright light you read your visual brain more effectively, you can see the letters better and help your eyesight.
Reference: “Image Brightness Turns Contrast Sensitivity Into Visual Cortex” by Hamed Rahimi-Nasrabadi, Jianzhong Jin, Reece Mazade, Carmen Pons, Sohrab Najafian, and Jose-Manuel Alonso, February 2, 2021, Self-reports.
DOI: 10.1016 / j.celrep.2021.108692
The study was conducted by Dr. Hamed Rahimi-Nasrabadi and collaborators in the laboratories of Jose Manuel Alonso, MD, PhD, at the State University of New York College of Optometry.