projecting on dark walls

yoskiwoski

Active Member
On the weekend I took the projector to a party in a bar , they had dark grey walls, i noticed that when projected on the dark wall the blcks were completely black and the whites were completely white, much better than when projected on a light wall , i was surprised i thought the whites in the picture would be the colour of the wall.
 

PJTX100

Distinguished Member
yoskiwoski said:
On the weekend I took the projector to a party in a bar
:eek:
yoskiwoski said:
, they had dark grey walls, i noticed that when projected on the dark wall the blcks were completely black and the whites were completely white, much better than when projected on a light wall , i was surprised i thought the whites in the picture would be the colour of the wall.

I think the brain tricks you into thinking they are white when they really aren't....PJ
 

PJTX100

Distinguished Member
Well if you prefer a grey projection surface it looks like you need to get going with a paintbrush then doesn't it?
...PJ :)
 

inzaman

Moderator
I thought this when i had an icestorm 5/6 mix screen (grey), sure the blacks looked blacker and the whites looked white, but when i compared it to the goo screen i had just made i realised that every other colour in the spectrum was dull or darker on the icestorm screen.
 

MacReady

Well-known Member
It is something to do with how the brain differentiates between lights and darks when they are next to each other. The whites may have looked white but would have actually been very light grey but because the blacks were deeper the brain saw the light areas as being very light....



....probably ;)

I think it is the same way this picture works that I had sent to me a while back.
 

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Peter Parker

Distinguished Member
That's a great picture to use as an example. I believe there's another picture from that example which shows a 'smear' that goes from 'A' to 'B', and you then see that the greys are in fact the same.

The eye/brain is easily fooled with colour and whites - if you look at your car and then go down to a paint shop to match the colour, you won't be able to (unless you have the paint code :) ). We also have the same trouble determining white when it may in fact be grey. We are less easily fooled by black though, and are more able to determine that black is more grey, and we can do this without a reference. With a grey screen, you won't realise the whites are grey until you place a white reference into the scene.

Inzaman - I wonder if the dullness you saw was not because of the colour, but because of the reduced gain? Does the Goo have some gain to it?

I have seen a 1.3gain Stewart Studiotek 130 screen alongside a Firehawk screen (it was a single, split screen), and the Firehawk didn't look dull at all (it's rated with a similar gain of around 1.3 IIRC). In fact, with a lot of ambient light on in the room, the Firehawk looked a lot better than the white screen because it appeared to reveal more detail - the white screen looked very washed out in comparison. That's one advantage of a grey screen - it visibly improves the black level without apparently compromisong the white level.

Gary.
 

inzaman

Moderator
Inzaman - I wonder if the dullness you saw was not because of the colour, but because of the reduced gain? Does the Goo have some gain to it?

Good point, i imagine that the grey screen would have been less than 1 gain, where as the goo was rated at 1.1/1.2 i believe.

I have just changed the Goo screen to a beamax fixed frame and this is slightly brighter still, which is 1.2 gain. This screen is also slightly smaller so that could suggest the slight increase in brightness.
 
K

Kobus

Guest
Goodness me, how is that optical illusion. I actually had to print the thing and fold the paper to convince myself.

Would love to see some more.
 

MacReady

Well-known Member
Kobus said:
Goodness me, how is that optical illusion. I actually had to print the thing and fold the paper to convince myself.

Would love to see some more.

Easiest thing is to drop it into something like Photoshop and look at the pantones of the two squares...exact matches.
 
P

ptek

Guest
Thanks Cleric for that illusion, thanks very much, now I can't sleep, if I close my eyes, is it black I see, or is it grey, perhaps its white looking like black ?
Thanks, just as my doctor said I was getting better ! :rolleyes:
 

PJTX100

Distinguished Member
Kobus said:
Goodness me, how is that optical illusion. I actually had to print the thing and fold the paper to convince myself.

Would love to see some more.

Picked up a 160 page book "optical Illusions" by Al Seckel just the other week in one of those discount book shops, think it was 2.99 or something. Some amazing illusions in it including the one above...PJ :thumbsup:
 

keylion

Active Member
Cleric said:
Easiest thing is to drop it into something like Photoshop and look at the pantones of the two squares...exact matches.

I have just dragged one square onto the other in paint as I didn't believe it.
 

inzaman

Moderator
I have just dragged one square onto the other in paint as I didn't believe it.

Thats what i did earlier, its just an amazing illusion :)
 

yoskiwoski

Active Member
the a and b arent the same colour i just checked in photoshop, the a is the same the light squares and the b the same as the dark ones.
 

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