How does this optical illusion work?

Ok it took me a while to “see” it at first, but now that I do I really am curious as to how it works. I also find it fascinating that zooming in and out makes it easier or more difficult to see.

I tried zooming way, way in on the image, to look for little pixels here and there, but the more I zoom in, the less I understand.

When I zoom way out (so that the image is small), I can see very clearly without having to do the trick to seeing it.

Here’s a hint on how to see it if you are not sure how:

If you can’t see it easily, blur your vision a bit by unfocusing on the screen

So, how does this work?

Optical Illusion Here

The illusion is in the white stripes, which very subtly change shade from white to light gray, making up the shape of the face. The black stripes break up the image enough that you don’t see the face when looking right at it, but unfocusing your eyes allows the white stripes to merge together enough so the pattern becomes visible

the white bars aren’t pure white - they change in shade quite a bit.
I opened it in Photoshop, and the difference is clearly measurable.

I have been figuring that out as well, and now I have lines in my vision… if you zoom way in & scroll the image, it’s easier to see the grey bits.

It’s a very, very feint grey and white image overlaid with solid black lines.

It’s also clearly measurable with the naked eye, you can see where the white lines are grey to create the image.

On my laptop (with an LCD screen) all I had to do was tip the screen way back and you couldn’t tell there was something wrong with the image to begin with.

Interesting. I was looking at it with my reading glasses on, close to the monitor and didn’t see anything. I took them off and saw what it was all about. Then when i moved back from the monitor I saw it more clearly.

I can’t really see anything but stripes, but, if people are saying that there is a faint gray picture of a face (?) superimposed on the black and white stripes, then, well, it is not an illusion, it is just a picture that has deliberately been made very hard to see.

Oh yes, I can see it when I take my glasses off too. Is it John Lennon, maybe?

Anyway, still no illusion going on.

Oh, is that how they make it? I tried to make one by making the black lines thicker. A band called Soulwax used this on their CD cover

This is what you get if you reverse the process:

It’s easy to see if you tip the screen back. Is it a pixel thing? Would it work if printed on paper?

BTW, if you zoom it out in Firefox, it won’t work, because Firefox is way behind the times in implementing resampling for smaller images. What I find surprising is how few images this makes a difference for.

(They oddly do resample when enlarging images–and they could use the same algorithm for shrinking images, but they don’t.)