Sometimes, it is remarkable how people stumble upon optical illusions. Optical illusions either accidentally appear to a person or when they are in the midst of their researching efforts in a particular field. For Professor Edward H. Adleson, the appearance of the Checker Shadow illusion was not accidental.

Studying anything mildly related to the field of visual perception was of great interest to him. During his research, he came upon the Checker Shadow illusion, and after carrying on an in-depth study of his own on the unusual finding, he published it for readers, scientists, professors, and his students so they too, could gain exposure to this optical illusion.

The Illusionary Effect of the Checker Shadow Illusion 
When he published the optical illusion, it appeared to be a checkerboard thus the name. In the picture, you will see that it is made up of both dark and light color squares. One square will appear darker in color than the other. Even though the two boxes appear to be a different color from each other, they are, in fact, the same shade. If you do not believe it, open it up in an image editing software.

The Proof of the Two Colors Being the Same
Copy the Checker Shadow illusion and paste it in an image editing software. Next, use the eyedropper tool to confirm that the two colors are the same. If you are upset over being proven wrong, take your frustration out on the illusion. 
You can take the effect of the optical illusion away by viewing patches of the black and white squares without the context surrounding it. You can even separate the squares from each other to eliminate the Checker Shadow illusion. Now, that you know that the colors are the same, you should know the working behind the optical illusion.

The Checker Shadow Illusion—the Explanation
According to Adelson, the visual system has one sole purpose—to distinguish the colors of the world. In his explanation, he writes that a cast shadow will dim an area in order to let a white area in a shadow reflect less light than a dark surface in complete brightness. In the Checker Shadow illusion, the light checkered boxes are surrounded by darker checkered boxes. Even if a checkered box is considerably darker, it is lighter when compared to its surrounding boxes and vice versa.  

Your visual system is ignoring the changes in the light level in order to determine the shade of the area without having the shadows misled it to thinking otherwise. Your visual system is breaking down the picture information into parts to view the nature of the object in front of it. 

The Checker Shadow illusion is one of the most sensational illusions, as it lets viewers perceive all the boxes as a different color when all of them are the same. You can feel free to dissect the optical illusion apart to see for yourself that the checkerboard is indeed one color.

Salvador Dalí, a Spanish painter and sculptor, has crafted several mesmerizing pieces in his lifetime, but one that stands out from the rest is the Hallucinogenic Toreador. The year was 1970 when the artist revealed his oil painting to the world. Just like his other artwork before this, the Hallucinogenic Toreador did not fail to impress the audiences. For art enthusiasts and fans of Dalí, there was something unusual about the oil painting, but in an artistic way.

The Hallucinogenic Toreador, One of Dalí’s Most Acclaimed Pieces 
Dalí’s inspiration for the subject of the painting was his wife. She loathed the idea of bull fighting, and Dalí used her hate as the basis for his painting. Using the paranoiac critical technique, he combined optical illusion, motifs, and symbolism. Once the oil painting was completed, it was time to share his unusual way of thinking with others.

The Hallucinogenic Toreador and How it Amazed People? 
Have you ever seen a bullfighting ring in real life? Perhaps, you have seen it in a movie or cartoon. If you really want to see a realistic depiction of a bullfighting ring, look no further than Dalí’s oil painting.

Since he used his wife’s hate for the sport of bull fighting, he drew her picture in the upper left corner of the painting. Her expression in the small portrait is rigid to show her hatred towards the sport. Every element of the oil painting is drawn inside a bullfighting ring. Through his painting, he also wanted to honor the Spanish flag. Hence, he ended up using yellow and red tones throughout the painting.

When the Painting Really Baffles You?
Those aspects of the painting do not stop the viewer dead in their tracks. It is the exaggerated version of blood and saliva dripping from the bull’s head that lies dying on the ground. In order for the viewer to look at the head as soon as they view the painting, Dalí drew a pattern of different colors, which force you to look down to see the bull’s agony. In front of your eyes, you see the blood transform into a bay. From the bay, arises a human sitting on a yellow colored raft. Below the bay, a visible outline of a Dalmatian appears.

The Peculiarity of the Painting Continues
However, that is not all, there’s more. The bull gradually transforms into the landscapes of Cap de Creus, which is where the painter resided with his wife. It is speculated that Dalí wanted to increase tourism in the area so he decided to paint the surroundings of the place he called home.

All the aspects of Dalí’s painting amazed people, as it was unlike any other painting they had ever come across. To this day, the Hallucinogenic Toreador attracts several visitors that come around from all over the world to look at it.

You can view the painting at Salvador Dalí Museum in St. Petersburg, Florida. The museum is dedicated to the work of Dalí and you will find plenty of his other thought provoking pieces on display. 

© opticalspy 2015

Celeste McCollough Howard, an American psychologist, was born in 1927. Throughout her career, she accomplished great feats. Out of all the feats she gained acclamation for, the McCollough effect was one of her greatest accomplishments. How did she come to discover the McCollough effect? For that, we have to look at how she arrived at it by going back to the beginning. 

Celeste McCollough:  Her Journey to become One of the Best 
Celeste McCollough was a driven and smart woman that wanted to excel at everything she put her mind to. Her knowledge of psychology led her to share it with others who had the same passion for the subject so she began to teach at Olivet College in Michigan.

After teaching from 1954-1956 at Olivet, Oberlin College awarded her with a full-time teaching position in the Department of Psychology, making her the first woman to join it. For research purposes, she left the college to visit Canada to research about perceptual effects of wearing glasses tinted with two colors. Her discovery became known as the McCollough effect.

What is the McCollough effect? 
The McCollough effect is a visual phenomenon where a person perceives colorless gratings as colored.  The person’s perception depends on the orientation and contingent of the gratings. In order to produce the effect, a person needs to be induced to see it. 

For instance, you look at a red vertical grating and a green horizontal grating for a few minutes, going back and forth between them. After a while, a black and white vertical grating will appear pinkish. For this reason, the effect has come to be known as one of the most remarkable effects to date.

The Popularity of the Effect Explained 
The McCollough effect is regarded as one of the most amazing illusions because its effects last for a long time. The effects might last for an hour or more, depending on the length of time you stare at it. In 1975, scientists, Holding and Jones, discovered that fifteen minutes of induction could increase the strength of the effect by three months. Furthermore, do not confuse the effect with colored afterimages, as both are two different phenomenons. 

Colored afterimages are superimposed and do not last a long time, whereas the McCollough effect does not do either of these. One thing in common between the two is that both require a period of induction to work. Due to the long duration of the effect lasting, scientists went into hysteria to find out how the effect was produced.

How the Effect Functions? 
With hundreds of explanations being thrown around about the McCollough effect, people narrowed down the barrage of explanations, saying that it was due to the sensitive neurons in lower monocular regions of the visual cortex. Additionally, another phenomenon came into existence, which was the anti-McCollough effect. 

Alternating pairs of grating in parallel alignment, one black and white and a single color either red or black induce the anti-McCollough effect. The perceived shade is the same as the inducer shade and the effect is weaker.

We bet you are now curious to try the McCollough effect, but do not stare at it too long, as you know what happens if you do.

Zoetrope is a type of pre-film animation device that creates the illusion of movement by producing a series of pictures or drawings to show progressive phases of a particular motion. The Zoetrope is made up of a cylinder with vertical cuts at the sides. When you look inside of the zoetrope, you will see a band with pictures from a set of pictures aligned in sequence.

The cylinder has to spin in order for the user to see the pictures move through the slits. Without the slits, the picture will blur together, preventing the user from seeing the picture clearly. With the slits, the user is able to see the images move when in fact, what they are actually seeing is an illusion of movement.

These types of devices have been in development since the 20th century such as 3D zoetropes and linear zoetropes. The type of zoetrope that will be discussed in detail is called the cylindrical zoetropes.

A Look Back in the History of the Zoetropes

Ding Huan, a Chinese inventor, invented a device called “a variety of zoetrope” in 100 BC. The function of this device remains unknown to this day. All people know is that something along the lines of moving pictures was invented. Next, came the British’s turn to invent something similar, which they accomplished in 1833 or 1834.

This time it was William George Horner, a British mathematician, who developed a drum-like shape of the zoetrope. By the time he came around to building it, he had prior knowledge of the phenakistoscope disc.

Horner’s version contained rotating discs with slits to view the pictures. He ended up calling his invention the daedaleum. His invention did not become a huge hit until the 1860s when an alternation to the device was made; allowing people replace the pictures with new ones. Milton Bradely, an English inventor, and William F. Lincoln, an American inventor, both filed a patent for it. The American inventor called his device zoetrope, which became an instant hit.

© opticalspy 2015 - Image sources unknown

At a young age, D.L. "Rusty" Rust was inspired to become one of the most accomplished artists in the United States. If someone asked what he wanted to be when he grew up, he was quick to reply—an artist. 

Born in Erie, Pennsylvania, Rusty influenced by the work of his grandfather, Emil Rust, received his grandfather’s ability and passion to draw and create work of art to impact people in a meaningful way. 

What better way is there to impact people than creating illusions? The artist in him recognized that. Therefore, he combined his passion for creating wildlife art and optical illusions, using oil on canvas to produce art that would resonate with viewers. 

The Wild Life of Rusty 
Growing up in Erie, Pennsylvania, Rusty was exposed to the wonders of outdoors—the beaver ponds, creeks, fishes, birds, grasslands, trees, swamps, and more. Wanting to incorporate the surroundings of the place he grew up in came naturally to him. 

The works of his grandfather and other artists such as Gil Elvgren, Norman Rockwell, and Bob Toombs also helped mold his work to what it is today. In fact, in his earlier paintings, you can see the influence of other artists, which he proudly claims to be one of his greatest assets in his growth as an artist. However, before he began to create wildlife, he painted circus and portraits, but since then he shifted his focus to reproduce nature in all of its glory. So far, his impressive resume includes wildlife, seascapes, illustrations, camouflage-type, pin-up, fantasy, still life, glamour, portraits, and nude paintings. 

You can revisit his earlier work, which is on display at the Ringling Museum of Circus in Sarasota, Florida, the National Portrait Gallery of the Smithsonian Institute in Washington, D.C., and the Norman Rockwell Museum in Philadelphia, Pennsylvania. 

If you would like to see more of Rusty's work take a look at our Donald Rust Gallery.