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Comment by mattkrause | Hacker News Reader

The one thing missing from these answers is that “spatial frequency” (as this is called in vision/neuroscience) is a biologically-meaningful concept too. Neurons in early visual areas extract spatial frequency information, and it’s maintained in (largely) separate channels as that information flows through the brain.

There’s a neat Dali painting which sort of abuses these properties to combine two portraits: http://archive.thedali.org/mwebcgi/mweb.exe?request=record;i...

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Another example of the same effect is this combination of Albert Einstein and Marilyn Monroe. The high frequencies are Einstein, the low are Monroe.

https://static.independent.co.uk/s3fs-public/thumbnails/imag...

Wow! If you're look carefully for a short time, it is only Einstein. If you look diffusely for a while, it is only Marilyn. (For instance, squint and move the image around)

Odd, I can’t seem to force my eyes to see Marilyn despite similar things working for me.

Try walking away from the computer and looking at it from far away. Here it is with increasing amounts of low pass filtering: https://i.imgur.com/orsZe0n.jpg

Ever since getting Lasik done, I struggle to de-focus my eyes. This one was especially tricky, but walking away from the screen did the trick. I’d done that before you suggested, but appreciate the suggestion as well as the link.

Crossing my eyes lets me see it instantly.

Ok that's the neatest artpiece I've seen all year. I need a print of this on my wall.

I honestly can't see Abraham Lincoln there, except the small portrait at the bottom left. Is that the point?

I just don't get modern art- anything after the impressionists. I normally make an exception for the surrealists, like Dali, but this one is not in the "exception" group, I think.

You have to be far away (20m away for the original) or squint a bit/cross your eyes and the big picture starts looking like the tiny portrait of Lincoln that you mention.

You can also save that picture on your device and look at the generated thumbnail. Resizing it makes it a lot more obvious.

Cheers, I managed to see it eventually.

For me to see Lincoln, I tried holding my phone at arm's length; it was better when my friend held the phone and I stood back

The small portrait is reproduced in the larger one. The pixels of the beard are around the bottom of the window, the ear is the lighter blocks to the left, and his right eye is her head in the center.

Thanks, I realised what the smaller portrait was after reading the helpful comments in this thread.

Lincoln is hidden in the low frequencies in the image. One way to filter out the high frequencies is to step back a bit from the display, another is to squint your eyes, resize the image, or just use a low pass filter in an image editor.

https://imgur.com/a/NK5GFGn

Or, if you're a myopic glasses-wearer, simply try on-off. I love this trick for images of all kinds because it allows me to apply a uniform blur, no computation required.

I can just let go of focus, like a thousand yard stare.

Thanks. I can kind of see it out of the corner of my eye if I move a bit further from the screen.

I guess that's what the pixelated portrait of Lincoln on the same page is then.

You might need to be further away (or try squinting).

Spatial frequency is often reported in cycles/degree. A cycle is one complete set of transitions (light->dark->light) and a degree is the angular distance (1/360th of a circle; about the size of your thumbnail at arm's length). These units are handy since they don't depend on the thing you're looking at or how far away it is.

Human spatial frequency sensitivity peaks between 1-10 cycles/degree, depending on how old you are, to see Ol' Abe, you ought to be far enough away that your thumbnail covers at least five of the tiles.

Thanks, I was able to see it by moving away from the screen a bit.

I feel terribly sorry for you... and then delighted for you once you see it!

Nope I still can't see it. Maybe downvote me a bit more because I can't see it? That might help.

https://news.ycombinator.com/newsguidelines.html

Still, be nice to the Goblynne Queen.

Think how frustrating it must be to hear other people say how cool something is, while not being able to see it yourself!

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