Crazy Illusions

Some videos which physically show and explain different kinds of illusions.
































Reference:

Strange View Optical Illusion. 2009. Available at:

http://www.youtube.com/watch?v=2LtJn83aM1w&feature=fvwrel. [Accessed: 22 May 2011]

Lines of Confusion Illusion. Available at:

http://www.youtube.com/watch?v=llonA5RtpUM&feature=relmfu. [Accessed: 22 May 2011]

Crazy Mugs Illusion. Available at:

http://www.youtube.com/watch?v=87OclSF3NCY&feature=fvwrel. [Accessed: 22 May 2011] 

The Room Illusion - BBC Brain Story

Reference:

BBC Brain Story. 2002. The Room Illusion [online]. Available at:

http://www.youtube.com/watch?v=6aJlX0AEWys&feature=related. [Accessed: 22 May 2011] 

Depth Perception

Depth perception is the ability to see the world in three dimensions and to perceive distance. Although this ability may seem simple, depth perception is remarkable when you consider that the images projected on each retina are two-dimensional. From these flat images, we construct a vivid three dimensional world. To perceive depth, we depend on two main sources of information: binocular disparity, a depth cue that requires both eyes; and monocular cues, which allow us to perceive depth with just one eye.

Binocular Disparity 

Perhaps the most important perceptual cues of distance and depth depend on so-called binocular disparity. Because our eyes are spaced apart, the left and right retinas receive slightly different images. This difference in the left and right images is called binocular disparity. The brain integrates these two images into a single three-dimensional image, allowing us to perceive depth and distance. The phenomenon of binocular disparity functions primarily in near space because with objects at considerable distances from the viewer the angular difference between the two retinal images diminishes.

Monocular Cues 

Monocular cues are cues to depth that are effective when viewed with only one eye. Although there are many kinds of monocular cues, the most important are 

Interposition

The most important monocular cue is interposition, or overlap. When one object overlaps or partly blocks our view of another object, we judge the covered object as being farther away from us.

Atmospheric Perspective

The air contains microscopic particles of dust and moisture that make distant objects look hazy or blurry. This effect is called atmospheric perspective, and we use it to judge distance.

Texture Gradient

A texture gradient arises whenever we view a surface from a slant, rather than directly from above. The texture becomes denser and less detailed as the surface recedes into the background, and this information helps us to judge depth.

Linear Perspective

Linear perspective refers to the fact that parallel lines, such as railroad tracks, appear to converge with distance, eventually reaching a vanishing point at the horizon. The more the lines converge, the farther away they appear.

Size Cues

Another visual cue to apparent depth is closely related to size constancy. If we assume that two objects are the same size, we perceive the object that casts a smaller retinal image as farther away than the object that casts a larger retinal image. This depth cue is known as relative size, because we consider the size of an object's retinal image relative to other objects when estimating its distance. Another depth cue involves the familiar size of objects. Through experience, we become familiar with the standard size of certain objects. Knowing the size of these objects helps us judge our distance from them and from objects around them.

Height Cues

We perceive points nearer to the horizon as more distant than points that are farther away fom the horizon. This means that below the horizon, objects higher in the visual field appear farther away than those that are lower. Above the horizon, objects lower in the visual field appear farther away than those that are higher. This depth cue is called relative height, because when judging an object's distance, we consider its height in our visual field relative to other objects.

Motion Parallax

Motion parallax appears when objects at different distances from you appear to move at different rates when you are in motion. The rate of an object's movement provides a cue to its distance. The more distant objects appear to move in a more slower pace.

Ambiguous Depth Cues 

The methods of depth perception discussed above rely on different views from different eyes. However there are other more subtle ways to make a two dimensional image "feel" three dimensional. These methods are called ambiguous depth cues and are used by artists to make their pictures appear more realistic. These techniques are called ambiguous because there is more than one way to interpret them and the brain prefers to see them as three dimensional. While the other methods of depth perception occur in the eye, these methods occur in the brain. The primary forms of ambiguous depth cues are size, brightness, shadows, perspective, the use of the straight line and obstruction.

Size

When an object gets farther away it focuses on a smaller area on the retina. As a result, we generally associate a smaller object with being further away.

Brightness

If a light source illuminates closer objects more than those further away, we see different shades of brightness and assume different distances from a light source. Colour can have a similar effect as through changing colours artists can create the illusion of fog and make a piece of a picture appear further away. 

Shadows

When a light source illuminates an object, it will not illuminate objects behind it. Shadows make one object appear to be in front of another and the shadow size determines the depth between them.

Perspective

As we look at the horizon, straight lines appear to converge. By converging lines in a picture, an effect of making them appear to move further away can be created.

A good example of perspective is the Ames room or the distorted room constructed by the ophthalmologist Adelbert Ames. The room from the front appears to be an ordinary rectangular room with a back wall and two perpendicular parallel side walls. However, in reality this rectangular appearance is a trick of perspective. The true shape of the room is trapezoidal with slanted walls and the ceiling and floor at an incline. The room is observed through a peephole in order to create the best viewpoint and remove any sense of depth which would otherwise be created if viewed through both eyes. The perspective illusion is often enhanced by adding additional clues such as a checkered floor and rectangular windows on the back wall. 

There is nothing surprising in our perception of the empty room as normal, for the image we see through the peephole is identical to that which would be received from a normal rectangular room. However, when people stand in the room there is a conflict. The person in the further corner has a smaller image, due to their greater distance from the observer as compared to a person in the nearer corner. What is surprising is that observers see the people distorted in size and the room retains its rectangular shape, presumably because we are used to seeing rectangular not trapezoidal rooms. Thus, an adult in the further corner will appear smaller than a child in the nearer corner. Ames and subsequent researchers used this phenomenon to demonstrate the importance of experience in perception.

The Straight Line

By curving a "straight" line, a two dimensional picture may appear to be bending into three dimensions.

Obstructions

Because we can not see around corners, an object will block your view of everything behind it. In a picture, the object that blocks your line of site must be in front.


Reference: 

http://www.newworldencyclopedia.org/entry/Ames_room. [Accessed: 21 May 2010]

Depth Perception [online]. Available at:

http://library.thinkquest.org/27066/depth/nlindex.html. [Accessed: 21 May 2011]

Introduction to Perception [online]. Available at:

http://www.sapdesignguild.org/resources/optical_illusions/intro_depth.html. [Accessed: 21 May 2011]

Depth Cues [online]. Available at:

http://psych.hanover.edu/krantz/art/cues.html. [Accessed: 21 May 2011]

Ames Room. 1997. Available at: http://www.psychologie.tu-dresden.de/i1/kaw/diverses%20Material/www.illusionworks.com/html/ames_room.html. [Accessed: 21 May 2011]

Optical Illusions

Illusions are the triumph of intellectual foolery, a split between perception and cognition which induces a state of temporary confusion. Any one aspect of a visual scene is spatial ambiguous, these is an innate ambiguity in retinal input which relies on spatial processing for us to make sense of the world. Generally one can encode three-dimensional information from two-dimensional situations, a powerful capability in itself, however illusions introduce a heightened degree of difficulty to the process of perception. Inverse Optics result when our perception and our logic struggle to impose order on a situation and an alternating view of the world is ensured.


Optical illusions bear the trade marks of deliberate visual deception - perceptual error i.e. the incorrect coding of visual information. It is an interesting to present some information on this area within the context of this study as it is the improper visual interpretation of a stimuli that leads into a spatial cul de sac and hence the barrier to acquisition of efficient spatial skills. They play a prominent part in our appreciation of the physical world. Sometimes they must be avoided, but often they may be put to work in various arts. Their widespread existence and forcefulness make visual perception the final judge in decoration, in painting, in architecture, in landscaping, theatre and lighting. 


Optical illusions are some times called "errors of sense" and some of them are such, but often they are errors of the intellect. The senses may deliver correctly but error may arise from imagination, inexperience, false assumptions, in correct associations and the recency, frequency, and vividness of past experience. The direct data delivered by the visual sense are light, intensity, color, direction. 


Next is the distinction of outline-form and surface-contents. The perception of these by the eyes is so direct and so certain that it may be considered to be immediate. A ring of points is apparently very simple and it might be considered a direct sense perception, but it consists of a number of elemental directions. The perception of solid-form is far more complex than outline-form and therefore more liable to error. It is judged partially by binocular vision or perspective and partly by the distribution of light and shade. Colors may help to mold form and even to give depth to flat surfaces. For example, it is well known that some colors are "advancing" and others are "retiring."


Perhaps of still greater complexity are the judgments of size and of distance. Many comparisons enter such judgments. The unconscious acts of the muscles of the eye and various external conditions such as the clearness of the atmosphere play prominent parts in influencing judgment. Upon these are superposed the numerous psycho-physiological phenomena of color, irradiation, e.t.c.


In vision, judgments are quickly made and the process apparently is largely outside of consciousness. Higher and more complex visual judgments pass into still higher and more complex intellectual judgments. All these may appear to be primary, immediate, innate, or instinctive and thus certain, but the study of the psychology of vision has shown that these visual judgments may be analysed into simpler elements. Therefore, they are liable to error.


In a broad sense, any visual perception that does not harmonize with physical measurements may be termed an "optical illusion." Therefore, this term could include physical optical illusions obtained by means of lenses, mirrors and prisms and also optical illusions such as the mirage. It could also include the physiological illusions of light and color such as after images, irradiation, and contrast, and the psycho physiological illusions of space and the character of objects.
  
In a more common sense, attention is usually restricted to the last group; that is, to the psycho-physiological illusions that include the perception of space with reference to the character of objects and sometimes motion is also considered.

Many examples of optical illusions may be found around us. Alot of artists have worked with this concept to create scenarios that deceive the eyes and thus create thought provoking, interesting compositions and structures. It is the main area of interest in terms of artistic practice for some graphic artists like M.C. Escher who played around with quirks of perception and perspective to create intriguing images. 

Ascending and Descending by MC Escher - 1960, Lithograph

Belvedere by MC Escher - 1958, Lithograph

Swans by MC Escher - 1956, Woodengraving

Print Gallery by MC Escher - 1956, Lithograph

Three Worlds by MC Escher - 1955, Lithograph

The works of MC Escher take the art of optical illusion to an aesthetically precise level. Through clever and intricate geometrical formation and interpretation of the principals of mirroring, shade and shadow his works transport the viewer into a somewhat deluded perception.


Another artist with a similar artistic style is Oscar Reutersvard. Reutersvard is known as the ' Father of Impossible Figures' as he fathered the art of impossible objects i.e. objects which appear to be solid in an image but are impossible to construct in reality. He is often compared to Escher however, there is a distinct difference in the styles of both as Escher used to create inhabited worlds around impossible objects whereas Oscar Reutersvard created pure geometric forms. 

Reference: 

Illusions [online]. Available at:

http://www.ul.ie/~mearsa/9519211/illusion.htm. [Accessed: 18 May 2011] 

Optical Illusions of Brightness and Contrast [online]. Available at:

http://www.visualillusion.net/Chap08/Page01.php. [Accessed: 18 May 2011]

Escher, M.C. Pictures [online]. Available at:

http://www.mcescher.com/Gallery/gallery.htm. [Accessed: 18 May 2011] 

A Father to Impossible Figures [online]. Available at:

http://butdoesitfloat.com/45963/A-father-to-impossible-figures. [Accessed: 18 May 2011]  

What is Forced Perspective? - Examples

The Tunnel of Typography by Otherthings

Out for a Stroll by Kevin Eddy 

Gnome Alone by -RobW-

Warp by kitone

Johan is incredibly tall by mrlerone

What Is Forced Perspective? -- powered by ehow

Reference:

Wilkins, R. 1999-2011. What is Forced Perspective [online]. Available at:

http://www.ehow.com/video_4973371_forced-perspective_.html. [Accessed: 13 May 2011]

Forced Perspective

Forced perspective is a technique that uses optical illusions to make an object appear farther away, closer, larger or smaller than they actually are. It makes objects of vastly different sizes, that are at significantly different distances appear proportionate through manipulating human visual perception. This is achieved by using scaled objects and developing a correlation between them and the vantage point of the spectator or camera.
Function
   A small object very close to a camera appears large while a big object far away appears small. Our brains usually understand that something is close or far based on relative perspective. In a picture of a skyline, we see everything small but know that buildings are really large. Our brains, therefore, see everything as big from a distance. However, bringing a smaller object closer to the point of view and giving the illusion that it is larger can trick our brains. This

is forced perspective.
   Forced perspective can be made more believable when environmental conditions obscure the difference in perspective. For example, the final scene of the famous movie casablanca takes place at an airport in the middle of a storm, although the entire scene was shot in a studio. This was accomplished by using a painted backdrop of an aircraft, which was "serviced" by dwarfs standing next to the backdrop. A downpour (created in-studio) draws much of the viewer's attention away from the backdrop and extras, making the simulated perspective less noticeable.
Effects and Features
   In photography, forced perspective can be achieved by positioning objects of different sizes and distances so that they appear to be right next to each other. An example would be placing a toy car close to the camera with a car dealership in the background. If placed correctly, the toy will appear to be a full-sized car. It is also a common photographic effect to make a person appear to be touching something large that is far away. For example, holding the moon in his hand or touching the top of a tall building.

 
   Forced perspective is a commonly used trick in films. Movie sets and location shoots are expensive. It is much cheaper to film actors in front of paintings, photographs or miniature models giving the illusion that they are in a much bigger place. Small objects can also appear to be very large by placing them close to the camera and shooting actors from far away. Old-time monster movies used to use this trick.
   This is a practical technique for shooting a scene in a studio with less space than might be required. How can that happen? Isn't the size of a studio predetermined by the number of sets scheduled to occupy the space? Initially, it is. Then any number of things could happen; the schedule changes or a critical location is lost or an additional series of shots are added to forward the storytelling. At that point, a forced perspective set might be squeezed into the empty space previously occupied by a set already shot and wrapped.
Role of Light 
   Early instances of forced perspective used in low-budget motion pictures showed objects that were clearly different from their surroundings, often blurred or at a different light level. The principal cause of this was geometric. Light from a point source travels in a spherical wave, decreasing in intensity or illuminance as the inverse square of the distance travelled. This means that a light source must be four times as bright to produce the same illuminance at an object twice as far away. Thus to create the illusion of a distant object being at the same distance as a near object and scaled accordingly, much more light is required.
   Opening the camera's iris lets more light into the camera, allowing both near and far objects to be seen at a more similar light level, but this has the secondary effect of decreasing depth of field. This makes near or the far objects appear blurry. By increasing the volume of light hitting the distant objects, the opening of the iris can be restricted and depth of field is increased, thus portraying both near and far objects in focus, and if well scaled, existing in a similar lateral plane.
   Since miniature models would need to be subjected to far greater lighting than the main focus of the camera i.e. the area of action, it is important to ensure that these can withstand the significant amount of heat generated by the incandescent light sources typically used in film and TV production.
Nodal Point: Forced Perspective In Motion 
Peter Jackson's film adaptations of The Lord of the Rings make extended use of forced perspective. Characters apparently standing next to each other would be displaced by several feet in depth from the camera. This, in a still shot, makes some characters appear much smaller in relation to others.
   A new technique developed for the enhancement of this principle which could be used in moving shots. Portions of sets were mounted on movable platforms which would move precisely according to the movement of the camera, so that the optical illusion would be preserved at all times for the duration of the shot. The same techniques were used in the Harry Potter movies to make the character Hagrid look like a giant. Props around Harry and his friends are of normal size, while seemingly identical props placed around Hagrid are in fact smaller.
   The techniques developed center around a nodal point axis, so the camera's panning axis is at the point between the lens and aperture ring where the light travelling through the camera meets its axis. By comparison, the normal panning axis would be at the point at which light would strike the film. The position of this nodal point can be different for every lens. However, on wide angle lenses it is often found between the midpoint of the lens and the aperture ring.
Forced Perspective in Architecture
   In architecture, a structure can be made to seem larger, taller, farther away or otherwise by adjusting the scale of objects in relation to the spectator, increasing or decreasing perceived depth. For example, when forced perspective is used to make an object appear farther away, the following method can be used: By constantly decreasing the scale of objects from expectancy and convention toward the farthest point from the spectator, an illusion is created that the scale of said objects is decreasing due to their distant location. In contrast, the opposite technique was sometimes used in classical garden designs to shorten the perceived distances along a path.
   Builders of ancient structures like the Pantheon, built stone columns curving slightly outward in the middle. This gives them the illusion of being straight and longer than they actually are. Symbols on temples were made larger the higher they were off the ground. This made all the writing appear to be the same size from the ground.
   The Statue of Liberty is built with a slight forced perspective so that it appears more correctly proportioned when viewed from its base. When the statue was designed in the late 19th century, there were few other angles from which to view the statue. This caused a difficulty for special effects technicians working on the movie Ghostbusters 2, who had to back off on the amount of forced perspective used when replicating the statue for the movie so that their model - which was photographed head-on, would not look top-heavy. A similar effect can also be seen in Michelangelo's statue of David. Forced perspective is extensively used in theme parks or other post modern architecture often to make structures look larger than they are in reality. The technique is used in instances where physically large structures may not be feasible or to provide an optical illusion for entertainment value. 


REFERENCE: 
Kay, N. 2006-2010. 15 Forced Perspective Techniques Example [online]. Available at: http://www.digital-photography-school.com/forced-perspective
http://en.wikipedia.org/wiki/Forced_perspective. [Accessed: 12 May 2011]
50+ Forced Perspective: Just Incredible Photography [online]. 2010. Available at:
http://desigg.com/forced-perspective-just-incredible-photography/. [Accessed: 12 May 2011]
Ninomiya, K. 1999-2011. What is Forced Perspective [online]. Available at:
http://www.ehow.com/about_4588026_what-forced-perspective.html. [Accessed; 12 May 2011]