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Friday, 08 January 2021

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Similar to the old U.S. flag "trick" with a yellow background field for the stars and green and black stripes.

Here's another fun one. Go in a dark room with your electronic flash. Point the flash away from you and look in that direction. Then trigger the flash with your eyes open and wait. The image will come back to you and persist for a while. If I remember correctly it appears in B&W.

It works much better if the color photo is negative. In very simple terms, your eye gets exhausted of looking at the same color for 30 seconds, and when you look away the inverse color is over-represented and briefly lingers until your eye recovers it's normal perception capacity. If the starting image is a negative, the BW version will briefly appear in the correct colors.

Cool...

Mike...you have a flash on your iPhone camera and you can force it on...

As far as your brain is concerned, it's all ones and zeros. Sorta like your computer.

Persistence of vision, that's what makes movies work. Stand a dowel on end and shoot a few frame, then lay the dowel on it side. Your brain will provide the missing frames, so that the dowel appears to swing from verticle to horizontal. This is one of the many valuable lesson I learned in film school. Other things are to shorten action shots. Pay attention to what is really happening when you see a match struck, or a bridge blowing up.

"Mike replies: I really want to try that but I have neither a dark room ..."

Mike Johnston doesn't have a darkroom? Truly, we are living in the end times.

The Impossible Color Wikipedia page is an interesting (and related) read.

It's possible, with a little practise, to view a stereo pair of photographs and see the 3D view, without a viewer. If you try this trick with a pair of identical photos, it will also seem to be a 3D view.

If you try this trick with a pair of photos that are identical except that one is about 8-10% longer and higher, the 3D effect is increased!

I found this last trick by accident here on TOP, when I clicked on a photo to enlarge it. The bigger version was only slightly bigger than the one I'd clicked on (this used to happen a lot here some years ago) but I tried anyway, with great success!

I did this yesterday. I think I'm still seeing the effects today.

Another fun example, here: https://webvision.med.utah.edu/2012/06/your-brain-develops-the-negative/

sorry Mike did not work for me at all

anyidea why?

i have the idea that if you had not proposed the effect it would not have worked

[Most likely because you moved your eyes. Try again, and keep staring steadily at one exact spot. --Mike]

I'm a bit late commenting here but Olafur Eliasson's "Big Bang Fountain" artwork relies entirely on visual persistence. You can find it easily on the web but it consists of a fountain viewed in a darkened room; the fountain erupts and is simultaneously lit by a flash lamp. After the flash the viewer "sees" the water frozen by the flash. It harks back to Edgerton's flash lamp photography (e.g. Milk Drop Coronet and also, to my mind at least, his sinister atom bomb test images - again can find these easily on the web).

Dave.

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