I found a link to this picture, and I’m fascinated by how it works. https://fbcdn-sphotos-a.akamaihd.net/hphotos-ak-prn1/s320x320/538378_2712373708365_1827579672_1643774_740072937_n.jpg
If you look at it from far away, or you change the zoom on your screen to make it small, or your eyes are out of focus, it will look like Marilyn Monroe.
But if you look from close up, or you zoom in on it, or you can focus very well, it will look like Albert Einstein.
How was it made? Here’s my guess: After looking at it a few times, in a few different ways, they seem to have started with a blurry picture of Marilyn. Then, they superimposed a bunch of thin lines from an Einstein photo, and lined everything up just right, so that the eyes and nose overlap each other, and Einstein’s mustache overlaps Marilyn’s mouth. The result is that if - and only if - you can see the lines, then you can see Einstein. But if the picture is to small or blurry to see the lines, then you see Marilyn.
My questions are:
Is this technically an optical illusion? If not, then what is it?
Anyone know of any other examples of this sort of thing?
I don’t know if it qualifies as an optical illusion, but with my reading glasses on I see a rather feminine Albert. With my reading glasses off, I see Marilyn.
It’s basically two images - one image is encoded as small details, and the other as large areas. If your eyes have good resolution, you see the details, and the image looks like Einstein. If you have bad vision, the details blur, and you are left with the other image - Marilyn.
Here is a similar image by Dali.
I’m nearsighted and it looks to me like Albert Einstein got his hands on some great moisturizer.
they are hybrid images.
Technically, no, it is not an optical illusion.
First of all, if we are being technical, the preferred scientific term is not “optical illusion” at all, but “visual illusion”. Most visual illusions, most of the things that laypeople call “optical illusions” are caused by peculiarities of the human visual processing system (in the brain, or in the retina, and/or by eye movements). A small subset of visual illusions are caused by the actual physical optics of the situation, and may properly be called “optical illusions” (an example is the straight stick that looks bent when half immersed in water, due to the differing refractive indices of water and air). Generally speaking, the visual illusions produced by the brain are both more impressive and of more scientific interest that the truly “optical” ones.
But, in any case, I do not think this is really an example of an illusion at all. It is rather, an example (a new and interesting one, to me anyway) of what psychologists and other visual scientists call an ambiguous (or reversible, or bistable, or multistable) figure: a picture or other representation that can be interpreted by the visual system in (at least) two different ways.
Here is a bunch of other ambiguous figures from Google.
Heavens! There are even two I drew myself (though I did not invent them) on the first screenfull. :o
njtt, thank you for clarifying the terms. But your examples, while indeed ambiguous, remain ambiguous regardless of distance or focus.
shijinn - That’s exactly it. Thank you! And now that I know what it is called, I can easily find it on Wikipedia at http://en.wikipedia.org/wiki/Hybrid_image, which surprisingly shows another hybrid of Marilyn Einstein, but from a different angle than the one I linked to above.
no, these are not ambiguous figures. rather, the two images interchange depending on your viewing distance. there is no need to ‘look for’ the other image, the details for one image simply fade as viewing distance increases, thus allowing the other image to be interpreted without obstruction.
It does not follow from the fact that these work in a different way from other sorts of ambiguous figure (of which there are different types, working in different ways) that they are not a subclass of ambiguous or bistable figures. Not all “classical” ambiguous figures require deliberate, active reinterpretation - the Necker cube, for example, will often reverse spontaneously, and is quite difficult to reverse at will - and all images (in the sense of pictures, external representations), including these “hybrid figures” in each of their guises, require interpretation of some sort to be recognized. These figures just induce the reversal by changing focus or viewing distance, instead of (as with the Necker cube, the duck-rabbit and others) changing the locus of attention. Moving your head back and forth is not deeply different from moving your eyes to foveate a different spot.
You’re M.C. Escher?! 
it is a matter of classification, but it seems to me there is nothing ambiguous about the OP’s hybrid figures. the differing amount of information your eye receives at different distances means you are processing different images, as opposed to the same image interpreted in different ways.
njtt and shijinn, you’re both making excellent points. Thanks again.
I suppose my GQ question was to ask what they’re called, and how they work, and that has surely been answered. How to classify them might belong in GD.
This, and many more “Optical Illusions,” in the broadest sense of the term, are showcased on the Visual Phenomena & Optical Illusionswebsite.
It is instructive to learn how the brain processes visual input, and frequently can be fooled by context to form a picture completely at odds with the known reality of the situation.
The last time we discussed this, someone linked to a tutorial for how to make these yourself in Photoshop. I don’t have time to dig it up myself, though.
I imagine that there’s still a bit of skill in making these well-- The Einstein-Monroe images linked in this thread benefit from having the eyes superimposed, for instance.
With my amblyopia, I see both pictures. Neat.