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In a very frequently photographed place use lighting for less
than 1/60th of a second every few seconds to expose or make
appear an object. Only cameras will see the object this way.
In one out of every 600 vacation photos in a particular spot:
ET!
also useful for haunted houses.
More like 1/100th of a second.
http://www.psych.ny...entation_intent.pdf
[mouseposture, Nov 01 2010]
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Annotation:
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But how are you going to mount a laser apparatus in the middle of the sky without it being visible? |
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I didn't realise the sky had a middle. |
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It’s in between the top of the sky and the bottom of the sky, I presume. |
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There's often clouds in the way. |
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You could, instead, put it 'way up in the middle of the air. |
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Why will people not see things if they're only illuminated for less than 1/60th second? Flashes from flashguns are much shorter than that and they're visible. |
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There's a lot written about tachistoscopic presentation of
subliminal visual images, but mostly in the psychoanalytic
and marketing literature; not strong on technical detail.
But I found a <link> that gives an actual figure for how
short
the stimulus presentation needs to be for people not to
see
it: seems to be about 10 msec. |
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Also, the trick probably only works if the image has about
the same average brightness as what it replaces (c.f.
[hippo]'s comment on flashguns) so you'd have to project
*continuously* and tachistoscopically *replace* the image,
rather than merely projecting tachistoscopically. |
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