DIY Screen Build Help - AVS Forum
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post #1 of 15 Old 03-04-2012, 11:42 PM - Thread Starter
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I am in the process of finishing my HT room with my next step to be building a DIY screen. I want to build a 141" 2.35:1 scope screen in which I derived the length and width numbers from one of the Projector Central calculators as 129.74 (L) x 55.21 (W). When I put the tape up on the wall per these dimensions for some reason the outline looks smaller than I thought which then got me thinking that maybe I didn't use the right calculator to get the numbers.

So I'm asking if anyone can point me in the right direction as to if these numbers look right. Also, if someone can help me identify the right calculator for creating a scope screen. Thanks in advance for your help.
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post #2 of 15 Old 03-05-2012, 05:24 AM
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141 x 60 = 2.35:1

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post #3 of 15 Old 03-12-2012, 12:13 PM - Thread Starter
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Quote:
Originally Posted by CAVX View Post

141 x 60 = 2.35:1

Thanks for your response. Again, I'm new to projectors...I'm assuming your calculation is desired screen diagonal dimension x screen height?

I just want to make sure I am using the right numbers to build a scope screen. Thanks.
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post #4 of 15 Old 03-12-2012, 03:38 PM
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Quote:
Originally Posted by psalm234 View Post

I'm assuming your calculation is desired screen diagonal dimension x screen height?

141" is the width and 60" is the height.
2.35 is the aspect ratio.
The diagonal is 153.2"

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post #5 of 15 Old 03-12-2012, 04:28 PM - Thread Starter
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Quote:
Originally Posted by CAVX View Post

141" is the width and 60" is the height.
2.35 is the aspect ratio.
The diagonal is 153.2"

Oh OK...that is why I was confused. It looks like i forgot to indicate that I want a 141" diagonal screen.
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post #6 of 15 Old 03-12-2012, 04:42 PM
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Quote:
Originally Posted by psalm234 View Post

Oh OK...that is why I was confused. It looks like i forgot to indicate that I want a 141" diagonal screen.

To get a 141" diagonal 2.35:1 screen, the screen is:
W = 129.7"
H = 55.2".

I just quickly re-read your first post and it looks like you are relying on a screen calculator for this.

How deep (long) is your room?
If I was doing this, I would take the room length and divide that by 3.68 to find the ideal height for the room. I would then find the ideal seating distance (which can be personal) somewhere between 2x and 3x the image height.

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post #7 of 15 Old 03-13-2012, 03:41 PM - Thread Starter
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Quote:
Originally Posted by CAVX View Post

To get a 141" diagonal 2.35:1 screen, the screen is:
W = 129.7"
H = 55.2".

I just quickly re-read your first post and it looks like you are relying on a screen calculator for this.

How deep (long) is your room?
If I was doing this, I would take the room length and divide that by 3.68 to find the ideal height for the room. I would then find the ideal seating distance (which can be personal) somewhere between 2x and 3x the image height.

My room's depth is approx. 17.7ft (212.4 in). So per your numbers the height would be somewhere around 57.72 in which equates to what width and diag?
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post #8 of 15 Old 03-13-2012, 06:31 PM
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Quote:
Originally Posted by psalm234 View Post

My room's depth is approx. 17.7ft (212.4 in). So per your numbers the height would be somewhere around 57.72 in which equates to what width and diag?

Height is 57.7"
Width is 135.6"
Diagonal is 147.4" diagonal

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post #9 of 15 Old 03-20-2012, 12:03 PM
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Quote:
Originally Posted by CAVX View Post

Height is 57.7"
Width is 135.6"
Diagonal is 147.4" diagonal

Would not that be a large viewing angle? 36 degree viewing angle will be around 16.5 feet, so if you are trying to put two rows of seats, the front seat would have large viewing angle...

Now I am new to all these and just learning...so please educate what I am calculating wrong. Thanks.
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post #10 of 15 Old 03-21-2012, 12:41 AM
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Quote:
Originally Posted by drriddhish View Post

Would not that be a large viewing angle? 36 degree viewing angle will be around 16.5 feet, so if you are trying to put two rows of seats, the front seat would have large viewing angle...

Now I am new to all these and just learning...so please educate what I am calculating wrong. Thanks.

I get 17.4' and no your not getting the concept wrong at all. 36 degrees is measured from the centre seat of the back row of the seating to the edges of the screen, so when you sit closer, the angle does increase.

I sit at 2x the image height and that is almost 62 degrees (61.8).

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post #11 of 15 Old 03-21-2012, 07:13 AM
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Now the recommended viewing angle is 36 to 46, so does it not bother you that much if you have viewing angle of >46, especially in 2.35:1 format. I was told that It will make very hard to encompass whole picture without moving your eyes side to side. Thanks
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post #12 of 15 Old 03-21-2012, 05:31 PM
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Quote:
Originally Posted by drriddhish View Post

Now the recommended viewing angle is 36 to 46, so does it not bother you that much if you have viewing angle of >46, especially in 2.35:1 format. I was told that It will make very hard to encompass whole picture without moving your eyes side to side. Thanks

As Mark said, the 36 degree viewing angle is the recommended viewing angle for the back row of a THX certified theatre. At home they recommend 40 degrees for 16:9 with good HD material, which equates to 52 degrees for scope in the same seat with a scope screen of the same height (and ideally using an A lens so the pixel density is the same).

Seating distance is also related to in terms of screen height ratios, and the older recommendation of sitting at a ratio of 3 x the screen height stems from the crossover point where the reduction of the image quality of film may start to become visible (grain, scratches, dirt, projector mechanics), verses the need for immersion (more is usually considered better). With high quality HD material the SH to seating ratio can be moved closer to 2.4 x SH (THXs 40 degrees as mentioned before).

As for sitting too close, we have a binocular field of view of 120 degrees, so sitting at 60 degrees isn't too close and you won't get a great deal of eye movement. You may however, start to see pixels or source material issues if they're there. Vertical viewing angle is where most discomfort can occur (looking up for long periods), so make sure your screen isn't too high (eyes falling around a third of the way up the screen).

Seating distance is just a recommendation, so sit where you feel most comfortable (experiment by projecting onto a wall and see how close you can sit to achieve what feels best to you). With 1080 material, you can sit in the same range as in a commercial theatre (2 to 4 x SH puts you in the average range of seats) so if you tend to sit in the centre of a theatre, that would be around 2.4 x SH. If you sit a bit further back, 3 x may be better.

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post #13 of 15 Old 03-21-2012, 05:34 PM
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Here's a pic (often used here).



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Originally Posted by elmalloc
Who says Cameron is "right" and why do we care about him so much - lol!

I trust Gary Lightfoot more than James Cameron.
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post #14 of 15 Old 03-21-2012, 09:30 PM
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Quote:
Originally Posted by drriddhish View Post

I was told that It will make very hard to encompass whole picture without moving your eyes side to side. Thanks

Our eyes are side by side on our heads and they move horizontally all day without issue. It is when we make them shift up and down that we get fatigued. IMAX is an example and why most IMAX films are short 20~40min.

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post #15 of 15 Old 03-22-2012, 06:52 AM
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Thank you for wonderful discussion. This really helps me better design my theater.
I really love IMAX immersive experience...is there a way to bring it to home theater?
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