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post #1 of 14 Old 10-24-2007, 11:38 AM - Thread Starter
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I just ordered the Optoma HD70. Question is....how can I mount it in my basement?

My room is 30' x 13' and the ceilings are 6'7" tall. do I have to mount it on the floor? What is the largest screen size I could go w/?

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post #2 of 14 Old 10-24-2007, 12:19 PM
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Quote:
Originally Posted by ice1874193 View Post

I just ordered the Optoma HD70. Question is....how can I mount it in my basement?

My room is 30' x 13' and the ceilings are 6'7" tall. do I have to mount it on the floor? What is the largest screen size I could go w/?

wow...with that low a ceiling and the HD70 offset you will not be able to have a very big screen unless you tilt the projector up at an angle...if you tilt it, you then would have to use keystone to square up the image which could cause you some picture quality problems...What range of screen sizes were you thinking? I have a 8ft. ceiling and my HD70 is ceiling mounted and it is 13'9" from the screen and the screen is 101" but it is also pretty low to the floor...I had first had my screen higher on the wall but I had to angle the pj upwards and it caused the picture to be un-square which required some keystone which I didnt like doing.

Take care,
Brian
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post #3 of 14 Old 10-24-2007, 12:23 PM
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Best way is when you get it hold it up and see how it looks, i have maybe a 7' ceiling and i have it tilted slighly up in front with a 92" screen and the screen is almost 3' off the floor, keystone is low like -2 vertical.
If you have your screen low say 2' or less you'll be ok.
Get the shortest mount you can find for sure, mines about 3" off the ceiling.
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post #4 of 14 Old 10-24-2007, 12:27 PM
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Quote:
Originally Posted by Bud-man View Post

Best way is when you get it hold it up and see how it looks, i have maybe a 7' ceiling and i have it tilted slighly up in front with a 92" screen and the screen is almost 3' off the floor, keystone is low like -2 vertical.
If you have your screen low say 2' or less you'll be ok.
Get the shortest mount you can find for sure, mines about 3" off the ceiling.

Yep...mine is a little under 2ft from the floor.

Take care,
Brian
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post #5 of 14 Old 10-24-2007, 02:36 PM - Thread Starter
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i'll check it out. my friend also has 6-7 ceilings but he has a sony projector. i hope it fits.

will a lens shift projector make a difference?

Panasonic 50PX50U 50" Plasma
Westy W3213 32" LCD
Optoma HD70 Projector

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post #6 of 14 Old 10-25-2007, 10:35 AM - Thread Starter
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is there a formula to figure this out? I was thinking like a 92" screen. given that, how high does the projector have to be off the floor?

Panasonic 50PX50U 50" Plasma
Westy W3213 32" LCD
Optoma HD70 Projector

Pioneer 1015-TX
Athena AS-F2.2 (Mains), C1 (Center), B1 (Rears)
Acoustec H100 Sub

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post #7 of 14 Old 10-25-2007, 10:51 AM
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Quote:
Originally Posted by ice1874193 View Post

is there a formula to figure this out? I was thinking like a 92" screen. given that, how high does the projector have to be off the floor?

The HD70 offset is about 30% so you take 30% of the image height and that is how high above the center of the lens the image will appear on the screen wall.

Example:

92" diagonal screen is 45" tall
30% is about 14"

If table mounted:
PJ is on a table 24" high.
Center of the lens is 1.5" above table.
Add 14" for offset

Image appears on screen wall 39.5" above the floor.
add 45 inches for image
Top of image is 84.5 inches above floor, too high for your ceiling so lower your table to 18 inches above floor and image will go to nearly the ceiling.

If ceiling mounted:
6'7" ceiling = 79"
Ceiling mounted PJ center of lens is about 4 inches from ceiling. 75"
Offset for 92" screen is 14". Top of image appears on screen wall at 61"
61 - 45 = bottom of image appears 16 inches from floor. Maybe low for more than one row of seats. Not too low for me!
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post #8 of 14 Old 10-25-2007, 11:47 AM
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Quote:
Originally Posted by reconlabtech View Post

The HD70 offset is about 30%....

Projector Central has it listed as 33%..... another site has 28%.... I've seen 37% mentioned many times on this forum... Please someone tell me what the heck is going on here?

Is 30% the new verdict on the HD70 offset? I installed my newest screen with the 37% calculation. No Keystone was needed. However, it was a PITA to get it right and I began to question whether or not 37% was accurate.
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post #9 of 14 Old 10-25-2007, 12:19 PM
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Quote:
Originally Posted by tattootearz View Post

Projector Central has it listed as 33%..... another site has 28%.... I've seen 37% mentioned many times on this forum... Please someone tell me what the heck is going on here?

Is 30% the new verdict on the HD70 offset? I installed my newest screen with the 37% calculation. No Keystone was needed. However, it was a PITA to get it right and I began to question whether or not 37% was accurate.


30% is what I use. I've never seen 37% on anything official I've read.

I originally heard 28% but 30% works fine.
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post #10 of 14 Old 10-26-2007, 05:26 AM - Thread Starter
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Quote:
Originally Posted by reconlabtech View Post

The HD70 offset is about 30% so you take 30% of the image height and that is how high above the center of the lens the image will appear on the screen wall.

Example:

92" diagonal screen is 45" tall
30% is about 14"

If table mounted:
PJ is on a table 24" high.
Center of the lens is 1.5" above table.
Add 14" for offset

Image appears on screen wall 39.5" above the floor.
add 45 inches for image
Top of image is 84.5 inches above floor, too high for your ceiling so lower your table to 18 inches above floor and image will go to nearly the ceiling.

If ceiling mounted:
6'7" ceiling = 79"
Ceiling mounted PJ center of lens is about 4 inches from ceiling. 75"
Offset for 92" screen is 14". Top of image appears on screen wall at 61"
61 - 45 = bottom of image appears 16 inches from floor. Maybe low for more than one row of seats. Not too low for me!


man - great response! thanks for the help

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Westy W3213 32" LCD
Optoma HD70 Projector

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post #11 of 14 Old 10-26-2007, 01:18 PM
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The percentage of offset is variable based on the image height. The further back you mount the projector, the larger the image and the larger the offset.

If you go to http://www.optomausa.com/distancecalculator.asp and use this tool it will help quite a bit.

Chuck

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post #12 of 14 Old 10-26-2007, 01:32 PM
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Quote:
Originally Posted by Chas821 View Post

The percentage of offset is variable based on the image height. The further back you mount the projector, the larger the image and the larger the offset.

If you go to http://www.optomausa.com/distancecalculator.asp and use this tool it will help quite a bit.

Chuck

Was that not obvious in my responses or did you not read the thread?
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post #13 of 14 Old 10-26-2007, 01:48 PM
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Sorry, but the percent offset is not variable. Offset is a constant percentage of approx 30% of image height. If your image height is 4', then the vertical distance from lens center to screen edge is 4' X .3 = 1.2 feet.
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post #14 of 14 Old 10-26-2007, 01:56 PM
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Ok, let's make sure this is clear here:

Image offset is a set percentage of the image height. Obviously, if the image size changes, the offset RESULT does too. The percentage does not change.

I stated that I believe the offset to be 30% and found that to be accurate for my setup. However, the calculator on the Optoma website seems to return results that show the offset to be 36%.

Go figure...
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