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Discussion Starter · #1 ·
Screen basics--


The mirrors reflect the brightness and passes it through the colour sheet...the colour sheet chosen will mute the overbrights from the mirror and will enhance the the RGB saturation ,contrast and brightness. ..the 1/8" plastic will enhance the colour sheets properties by removing the harshness of the mirror-coloursheet combo.. and mute any unwanted reflctions from the mirrors.[physics 101.. reflected light slows as passing through the plastic.]


End results A 16:9ar screen size of 60"h x 106"w will offer you a 4:3 size of 60"h x 80"w with 13" of drapers as maskings on either side.


Masking the sides for 4:3ar is simple to do with just electric draw drapes easily purchased from any drapiery store. As the height remains the same in both 4:3 and 16:9.. sides are the only area needing masking.


Stuff;

Several cartons of 12"mirror tiles-In my case enough to make a 72"h=12x6 by 108"w=12x9 [or get a thin wall mirror made to dimensions easier but more bucks.] mount tiles on 1/4" plywood or equivalent using window putty as backing compound [DO NOT use the adhesive supplied it will not create a flush surface]

Once the correct area is laid, place a cloth over the mirror face and then a 2nd ply sheet over on the face of mirrors and slowly [so as not to crack the mirrors] lightly compress being sure to apply equall pressure to all areas [ I used a water fillable lawn roller myself worked fine].

This will flatten the tiles into the putty creating a flush mirror surface. once this stage is complete and before the putty sets, remove the flattening board and wash mirrored surface to take off any putty that may have squeezed out ...now go have a beer and let it set for awhile.

Then place a 1/8" clear plastic sheet[ONLY 1/8 thick as thicker will produce unwanted light bounce]-[available in 6'x12'size at most plastic places] over mirrors to create screen face use removeable clamps to attach plastic untill you have chosen the colour screen you wish to use.


Now all that you need do is find the best colour bedsheet to suite your taste -or simply use a white sheet and paint it the colour you prefer for your viewing.


I will not get into "which colour here" as it has been beaten to death in other threads and has mostly to do with personal prefferance anyway but greys are the most obvious choices for good balance.


Easy to experiment here.. as sheets are cheap and this system allows for easy swapping of colours without the hassle of "off again on again" work.

Once you are happy with your colour choice you can sandwich the coloured sheet between the plastic and the mirrors permenently.


You have the option of painting the plastic but once painted you cannot change colour without buying more plastic.[not cheap]


So far as masking goes its much simpler to mask the edges of a 16:9 to create a 4:3 than the other way around.

Chose my dementions by picking the height wanted for viewing the 4:3 ar and the width need to acomodate that height for 16:9ar

Now any need for masking will be on the sides and only for 4:3 viewing as the 16:9 and the 4:3 share the same height.


In short "create a 16:9 screen that keeps you happy with your 4:3 size" then side mask.


60"h 4:3ar needs 80w =100"diag ...you take the 60"h and calculate the width needed for 16:9ar at the 60"h which = 106"w =122.5"diag.

this means you will only need to mask sides for the 4:3ar. as the 16:9 fits screen h as does the 4:3.


"MIND"... your pj must be able to handle the 122 diag at 16:9 ...most will as this screen has great brightness without contrast loss... and colour saturation is excellent.


So i made my screen backing 72"h [6x12tiles] by 108"w [9x12tiles] and used short nap black velvet to mask in the correct dimentions 60"h x 106 of course if your good at cutting those mirror tiles you can get more accurate than I and less need for masking the correct dimensions.


I found masking in the dimensions easier as you can do this while screen is up and mask it to the projected pictures size perfectly

In my case i chose to sandwich a simple medium grey percale bed sheet [ask the wife she knows what percale is] for those wishing to use paint simply paint a good quality [percale] white bed sheet if this makes finding the right colour to suite your viewing easier.
 

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Quote:
Originally posted by D_Hod
...now go have a beer
Great advice...Thanks!
 

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You don't get any harsh reflections off of the 1/8 plastic?


b2b
 

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Don't forget the 'Blue Shift' that occurs when passing light through -all- semi-opaque to opaque materials. No exceptions. Physics does not allow any other outcome.


If you think I am being dense, there is no such thing as truly opaque materials. Even black holes have color shift problems.....


The thickness of the plexi makes it fuzzy and blue-shifted.


But what do I know about light and screens? Nothing I guess......
 

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Now I am dense...what exactly is this all about?
 

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Refraction will be minimal at best. Using a laser to align the projector 90 degrees to the screen will help this out. If shooting from the top or bottom then refraction becomes an issue and could cause colors to run or become all screwy. :) That's the one thing Ive been worried about with mirrors or any high reflective backing.
 

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Quote:
Originally posted by KBK
Don't forget the 'Blue Shift' that occurs when passing light through -all- semi-opaque to opaque materials. No exceptions. Physics does not allow any other outcome.


If you think I am being dense, there is no such thing as truly opaque materials. Even black holes have color shift problems.....


The thickness of the plexi makes it fuzzy and blue-shifted.


But what do I know about light and screens? Nothing I guess......
I painted my black hole material screen with ME and see no blue shift, my seating distance at event horizon


Pierre
 

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Quote:
Originally posted by SDB
Umm, no it doesn't. I'd get a refund for that class :)
Well, he's right actually. The index of refraction of a material is defined by the speed of light in vacuum c divided by the speed of light through the material v: n = c/v. "Normal" glass has an n of somewhere between 1.45 and 1.6 IIRC.
 

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Discussion Starter · #11 ·
Tryg got the point ...the beer compensates for any shift errors


mrmike Well gets an "A" for over the top thinking.

btw.. slowing the light

allows for better stauration as the light collides.


SDB... you flunked-out!...big time


and KBK .... opaque by definition means not allowing -any- light through and semi-opaque does this really exist

V

o·paque ( P ) Pronunciation Key (-pk)adj. --- Impenetrable by light; neither transparent nor translucent.


Iam thinking those smoked mirror tiles may make for a nicer screen will test and see this weekend


and just a note on black holes...your standing too close to the person infront of you if you can see 1.
 

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Quote:
Originally posted by D_Hod
Tryg got the point ...the beer compensates for any shift errors


mrmike Well gets an "A" for over the top thinking.

btw.. slowing the light

allows for better stauration as the light collides.


SDB... you flunked-out!...big time


and KBK .... opaque by definition means not allowing -any- light through and semi-opaque does this really exist

V

o·paque ( P ) Pronunciation Key (-pk)adj. --- Impenetrable by light; neither transparent nor translucent.


Iam thinking those smoked mirror tiles may make for a nicer screen will test and see this weekend


and just a note on black holes...your standing too close to the person infront of you if you can see 1.
Sorry, the only thing I get is a horrible reflection off of the plastic sheet.


b2b
 

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Quote:
Originally posted by mrmike
Well, he's right actually. The index of refraction of a material is defined by the speed of light in vacuum c divided by the speed of light through the material v: n = c/v. "Normal" glass has an n of somewhere between 1.45 and 1.6 IIRC.
Correct, the absolute index of refraction formula is n=c/v but the reflected light isn't slower through the plastic (glass) as he states. It's the same speed going in both directions (slower than c). The reflection doesn't change the speed, the plastic (glass) does. He is saying don't re-invent the mirror when he was doing just that.


It was a joke aka the :) factor


I love people that quote formulas! You guys rock!
 

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KBK wrote:

"But what do I know about light and screens? Nothing I guess......"


Ken, you have forgotten more than most of us could ever aspire to know.


And I mean that in all seriousness...
 
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