Vision deficiency

Seeing Is Not What It Seems

Gianni Sarcone

Color is energy—an electromagnetic phenomenon shaped by how light is reflected from objects. What we call vision is not innate. It is largely learned, built through a slow and demanding process. We tend to take it for granted, yet someone born blind who later gains sight must spend years learning how to organize and interpret what now enters the eyes.

Seeing is neither simple nor passive. When we look at a landscape, color information reaches the visual cortex in roughly 30 milliseconds (in the occipital lobe, V1). Only a fraction later—around 70 milliseconds—shape, depth, and motion begin to emerge. In these brief intervals, the brain filters, compares, and reconstructs fragments of data, assembling them into a coherent image. What we perceive is not a direct recording of reality but a refined interpretation—an internal best guess shaped for meaning and action.

The way we see

I’ve long been intrigued by the way people with partial or total visual loss engage with the world. Any serious reflection on perception or optical illusion eventually meets its counterpoint. Understanding how they “see” without sight reveals the real weight of vision itself—and how inseparably it works with the other senses, each one calibrating the rest.

When we see, move, speak, and feel at once, what actually binds sight to touch or hearing? The truth is, we notice far less than we assume. We attend only to what matters in the moment. Without the constant support of the other senses, perception would collapse into confusion, because they operate quietly in the background, guiding everyday behavior.

A striking example comes from research on inattentional blindness. In a well-known 1999 experiment by Daniel Simons and Christopher Chabris, participants watched a video and counted basketball passes between two teams. Nearly 40 percent failed to notice a person in a gorilla suit walking through the scene, pausing, even dancing, before exiting. The demonstration is disarming in its simplicity: we do not see what we do not attend to—even when it stands directly in front of us.

→ Source.

Magic Tic-Tac-Toe

Gianni Sarcone

Our visual system can interpret colors and shades in surprising ways. This 3×3 Tic-Tac-Toe grid, for example, showcases how easily our perception of brightness can be fooled.
Do you notice anything unusual in the grid below?

Show / Hide the Trick

The looping animation below brings the illusion to life, revealing the trick in action. That large green square behind the grid isn’t actually uniform—it’s made up of alternating dark and light green squares.

Our visual system works like a “comparative computer”. In fact, we never see colors in isolation, as the appearance of any color is affected by the colors surrounding it. So, under certain conditions, colors that are identical may appear different, while colors that are different may look the same. In our visual system there is a mechanism that enhances the contrast of the outline of an object relative to its background: it is called “lateral inhibition”.
Thus, even small differences in brightness between adjacent zones, or objects, are deliberately increased by our visual system and the brain to better distinguish them. But something strange happens when the brightness boundaries of the color zones are concealed: the cues the brain needs to trigger the lateral inhibition no longer exist and consequently we become blind to variations in color brightness, as shown in the animated gif.

Recognitions
My optical illusion “Magic Tic-Tac-Toe” has been chosen to be among the top 10 finalists for the “2019 Best Illusion of the Year Contest”

Emerson’s Secret

Gianni Sarcone

When Crayola‘s senior designer Emerson Moser retired in 1990—after 37 glorious years of loyal service—he finally confessed to a little secret: he was color vision deficient! Moser went on to produce a record 1.4 billion crayons during his career…
While any type of color vision deficiency (color blindness) could make crayon production difficult, complete color vision deficiency, where someone can only see in shades of gray, is extremely rare. About 99% of color vision deficiency involves just the inability to distinguish between some pairs of complementary colors.
So, if you’re wondering about your own color vision, feel free to take the test on my website.

crayola crayons

What color does it look to you?

Gianni Sarcone

1 in 12 people have some sort of color blindness that makes them unable to distinguish certain colors or shades of colors from others. Color blindness is, however, an inaccurate term to describe a lack of perceptual sensitivity to certain colors; a more precise term is: Color Vision Deficiency (CVD). Color blindness is the most commonly used term though it is misleading if taken literally, because colorblind people CAN see colors, albeit they cannot make out the difference between some couples of complementary colors. Color vision deficiency is not related to visual acuity at all and is most commonly due to an inherited condition. Red/Green color vision deficiency is by far the most common form, about 99%, and causes problems in distinguishing reds and greens. There is no treatment for color vision deficiency, nor is it usually the cause of any significant disability.

The most commonly used test to detect color vision deficiencies is the Ishihara Color Test.

Color vision deficient people have a tendency to better night vision and, in some situations, they can perceive variations in luminosity that color-sighted people could not. In fact, most color blind people can easily read what is written in the dotted pattern below… If you fail the test, that means you probably have the full range of color sensitivity that is attributed to color-sighted people.
[Highlight the blank space to see the answer: NO]

Reverse Ishihara Color Test