Is it optical illusions or visual phenomena?
Anamorphosis
What to see
The neighboring picture by Hans Holbein is called “The Ambassadors”. Every thing is painted very realistic, in trompe-l'oeil style. But what is the strange shape in the bottom foreground?
What to do
You could try a slanting look on the image from top right. Easier: further down I have cut out this shape; with the slider at the right you can change its angle, with the slider at the bottom its horizontal scale. This allows you to make the shape recognisable. Two tips: (1) set both sliders to rather low values, (2) memento mori.
The shape is rendered with a strong perspective distortion, an example of an anamorphotic display. Now in the National Gallery in London, the painting originally hung at the bottom of a staircase, so when descending the angle was just so.
Anamorphotic images can also involve mirroring on curved surfaces, cylinders or cones.
Blotted Letters
These look like random shapes... until you move the mouse over them.
The effect presumably is related to the fact that the borders of letters vs. background are indistinguishable from the borders of letters vs. ink blot.
Blur and Picture Content
Painting “All is Vanity” by Charles Allen Gillbert (1873-1929). Place mouse over image and observe the change.
This is not an “optical illusion” proper, it’s more a physical effect. With the strong spatial low-pass filtering, the blurred version simply lacks the fine details. However, one could also argue that the low-spatial frequency information is masked by high spatial frequencies like in the “Lincoln effect” by Harmon & Julesz (1973).
Def Leppard album "RetroActive"
Wotherspoon "Gossip, and Satan came also"
Wotherspoon "Society, a portrait"
Dali "Voluptate Mors"
Dali "Ballerina"
Cher, album "Heart of stone"
"L" Amour de Pierrot
Au revoir!
"La famille Impériale de Russie"
Cat or Couple?
French postcard (on Planet Perplex)
Judge Magazine cover, 1894 “Death to our industries!”
Enigma
Stare at the centre of the figure for a while. Some "scintillating" activity will build up in the violet and blue annuli. Some observers also report a circular rotation within these regions, things will begin to “run around in circles”.
This image “The Enigma” is by Isia Leviant (1981), Palais de la Decouverte, Paris.
Face on Mars
In 1976 the Viking Orbiter radioed back many images from Mars. Among those form the Cydonia region, one depicted a rock formation that strongly resembled a human or humanoid face staring straight up into the heavens.
You can probably guess what was made of this… "Pareidolia" is the term for neurological or psychological phenomena where vague images are interpreted by the brain as specific images. Statistically speaking, it is a type I error, a “false positive”.
A nice article “Paranormal Phenomena: The Face on Mars, Once and for All” contains some background material on the ensuing kerfuffle, including links to large NASA images of the entire regions photographed.
In 1998, the Mars Global Surveyor (MGS) reached the Red Planet with far better, more high-resolution equipment than Viking had carried. Initially, NASA had not planned to re-map the Cydonia region, but public outcry was so great that in April 1998, the MGS was programmed to re-photograph segments of the Cydonia region, including at least one of the face. If you move the mouse over the adjacent figure, the newer photo appears, roughly shifted and rotated to match the one taken 22 years earlier. You can judge for yourself whether you interpret this as a face about 2.5 km tall, 2 km wide and about 0.5 km of height.
Of course, none of the inevitable conspiracy theories was quenched by the new image.
Face in Beans
Find the face among the beans.
The picture is accompanied by all sorts of inferences on your mental development depending on delay until you find the face in there, which are even though they begin with “According to recent medical evidence”.
Can you see a face in beans?
Face in Blocks
What to do & observe
Observe the figure on the top right. It’s just a number of brownish blocks. Click once on the button "finer" ( if you have a editing application). Recognisable now? Perhaps if you deliberately blur the image, by screwing up your eyes or squinting? Yes, still too difficult. Go finer, and try after every step if it becomes recognisable via blurring.
This demonstration is based on the “Lincoln illusion” first reported by Harmon & Jules 1973. More generically it’s referred to as “block masking”. Since you have some training now, try blurring the black and white figure on the left. Another well-known face? Well, that was easy, since you were (or your visual system) was primed.
It seems plausible that the high spatial frequencies of the block edges reduce the signal-to-noise ratio for the "real" content. Blurring acts as a low-pass filter, reducing the high masking frequencies. In this respect the present phenomenon differs from “Blur and picture content”, because there the high spatial frequencies don't just mask, they also contain content.
This is the result of editing the picture :
It is simple, right?
Are you think this post above about optical illusions? or visual phenomena?
To be able to differentiate optical illusions and visual phenomena, follow my post next week.. okay?
God Bless us.. ^^
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