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crazy window perf illusion

Geneva Olson

Geneva Olson

Expert Storyteller
We recently installed printed window perf on the outside of this apt complex. The windows are crapped up so they wanted to cover them. They later asked for us to install plain unprinted window perf on the inside to block out some of the light. This was the result. Check out the pictures. The big circles are the window perf holes.
 

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BigNate

New Member
Geneva Olson said:
So...i'm not a science person at all. how did this happen? LOL.
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it is in interference pattern between the screens - where a hole and a solid align there is a shadow area, where the holes see through holes there is a light area.... this is also complicated a bit as you have an effect from the light projected onto things as well as almost a holographic image of the moiré light coming directly to your eyes... the pic on the right shows some different patterns at different amplitudes - there is a linear pattern of almost straight lines that is not too dark, then the big circular ones....

when printing with screen patterns, the angles of the screens relative to each other have to be optimized to reduce this effect - or we would see it on all half-tone screened prints.
 
Geneva Olson

Geneva Olson

Expert Storyteller
BigNate said:
it is in interference pattern between the screens - where a hole and a solid align there is a shadow area, where the holes see through holes there is a light area.... this is also complicated a bit as you have an effect from the light projected onto things as well as almost a holographic image of the moiré light coming directly to your eyes... the pic on the right shows some different patterns at different amplitudes - there is a linear pattern of almost straight lines that is not too dark, then the big circular ones....

when printing with screen patterns, the angles of the screens relative to each other have to be optimized to reduce this effect - or we would see it on all half-tone screened prints.
Click to expand...
ok. so what would have happened if we would have printed an image on it? would we have lost the image? because of the half tone effect?
 
JBurton

JBurton

Signtologist
Geneva Olson said:
So...i'm not a science person at all. how did this happen? LOL.
Click to expand...
I've always noticed this while peeling the backing or rolling up scraps. It's like an offset that isn't perfectly horizontal will cause the top row to have 10% overlap, with 1% increase on each row going downward, causing a different offset left to right, that in the end produces these (not random) random circles.
My question is, does the customer hate it?
Also, does it induce motion sickness going up the stairs?
 
JBurton

JBurton

Signtologist
Geneva Olson said:
ok. so what would have happened if we would have printed an image on it? would we have lost the image? because of the half tone effect?
Click to expand...
It would have had 'illuminated' regions where more light is coming through, so it would 'ruin' the print in that respect. I think a busy print would help make it less noticeable, but you'd definitely have the light effect still.
I bet it looks even better from the outside after dark.
 
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BigNate

New Member
.... a weird similar illusion happens when driving past a regularly planted orchard - if you glance at the orchard you can easily see straight down or across the rows, as would be expected if all the trees are printed in a large grid.... but look at different angles as you drive past and you will see brief glimpses of straight paths at various angles.... If you can imaging 2 sets of light sources coming through 2 adjacent orchards - projecting in the straight lines you can see through.... the Moiré pattern is made by the intersection of these light rays - areas that get light from 2 sources is brighter, areas that are lit up from 1 orchard are the greys, and the darks are areas that receive no light.... (the perf pattern on 2 different windows works like the orchards....)f
 
Geneva Olson

Geneva Olson

Expert Storyteller
JBurton said:
I've always noticed this while peeling the backing or rolling up scraps. It's like an offset that isn't perfectly horizontal will cause the top row to have 10% overlap, with 1% increase on each row going downward, causing a different offset left to right, that in the end produces these (not random) random circles.
My question is, does the customer hate it?
Also, does it induce motion sickness going up the stairs?
Click to expand...
The customer thought it was trippy. The windows had a haze on it that looked awful. So, they asked us to put this up just to cover up the ugliness of the windows. AND, they said the sun was coming directly in so they wanted more blockage.

I'm surprised that they are happy with it. But it looked worse before.
 
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BigNate

New Member
Anytime you have 2 screened sources of light there will be interference patterns, you can minimize them by trying different angles, different screen frequency (not practical with perf)... to eliminate it entirely on a window you would have to 100% match hole-for-hole (dot-for-dot in printing terms....) front side-to backside of glass. (also not very practical)
 
Moze

Moze

Active Member
I've probably posted this before but it's kind of along the same line of unexpected results. Had a bunch of doors with etched glass for privacy. The customer wanted "Restricted Access" signs on the door. The sign company shipped me clear vinyl with printed text. Turns out if you put clear vinyl on etched glass, it's not so private anymore.

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Geneva Olson

Geneva Olson

Expert Storyteller
Moze said:
I've probably posted this before but it's kind of along the same line of unexpected results. Had a bunch of doors with etched glass for privacy. The customer wanted "Restricted Access" signs on the door. The sign company shipped me clear vinyl with printed text. Turns out if you put clear vinyl on etched glass, it's not so private anymore.

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werid. I thought that was a reflection!
 
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