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Need screen size calc help

866 Views 7 Replies 4 Participants Last post by prismasonic, May 22, 2007

uabcar

Discussion Starter · May 21, 2007

Hoping someone can help me calc how large a screen I can have. I'm trying to achieve a somewhat low cost 2.35 add-on to my existing HT. I'm considering the Key Digital HDMI Switcher/Scalar and one of the inexpensive MonoPrice screens. Not sure what to do for lenses yet. My intent is to use my existing fixed mount screen for most viewing and the 2.35 screen for movies shot in that format.

Here are a couple setup details:

- PJ = Sanyo Z5

- PJ Lens in only 9.5 ft from the screen- ceiling mounted PJ (due to room constraints)

- Current fixed mount 16x9 screen is 92" diag. and required about 80-85% of my zoom to achieve

- 2.35 screen would need to be mounted 2-3 inches in front of my current screen making the effective thrown closer to 9.25ft.

Given my short throw, I'm concerned that I may not be able to achieve the screen size I want and therefore it may not be worth the investment. My hope is that I can use the MonoPrice 108" 16x9 to do a 94x40 2.35 screen. I'm just not sure how to go about determining if I can project an image that size. I'm not sure how to calc the impact the lenses will have- and which one's to get.

Can anyone help with the math?

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stanger89

· #2 · May 21, 2007

First, I'm assuming you're going with the "gheto" CIH (ie zooming), without running any of the numbers, if you're at 80-85% max zoom, you're not going to get much more size.

Now, if you're getting an HE lens, no problem than, you can easilly maintain the same height and get a 33% wider image.

One good way to visualize it, go to projector central and play with their projector calculator. You can tweak the zoom and such to see exactly how much difference zooming and whatnot will make.

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uabcar

Discussion Starter · #3 · May 21, 2007

That's the issue- I'm looking to go with lens and a scaler - want to keep all the resolution and lumens I can. After reading through the posts, It seems that your throw distance is impacted by lenses. Since I'm already nearly at max zoom, and will be effectively compressing my throw distance (due to the HE lens being a few inches closer to the screen and the 2.35 screen being placed a couple inches infront of my current fixed screen.

Let me ask this, when measuring throw distance via the ProjectorCentral calculator, do I input the distance between the HE lens and the screen or my PJ lens. Guess I'm confused how to convert the impact of 2.35 to the Pjcentral output.

Sorry for the noob questions and thanks for the help.

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stanger89

· #4 · May 21, 2007

Quote:
Originally Posted by uabcar /forum/post/0

That's the issue- I'm looking to go with lens and a scaler - want to keep all the resolution and lumens I can. After reading through the posts, It seems that your throw distance is impacted by lenses. Since I'm already nearly at max zoom, and will be effectively compressing my throw distance (due to the HE lens being a few inches closer to the screen and the 2.35 screen being placed a couple inches infront of my current fixed screen.

OK, you've got two options when it comes to lenses, Horizontal Expansion and Veritcal Compression, HE and VC. If you go with an HE lens, it effectively makes the throw shorter, ie at the same distance the image is bigger. What an HE lens does is take the same height image, and make it 33% wider.

Quote:
Let me ask this, when measuring throw distance via the ProjectorCentral calculator, do I input the distance between the HE lens and the screen or my PJ lens. Guess I'm confused how to convert the impact of 2.35 to the Pjcentral output.

It's really got nothing to do with the location of the lens, the important factor is expansion/compression factor.

Basically, setup PJC for your config without a lens (9.5 ft, 92").

Then, with an HE lens, multiply the reported width by 1.33 to get the width with lens.

For a VC lens, multiply the height by 0.75 to get the new height.

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uabcar

Discussion Starter · #5 · May 21, 2007

Okay- think I've got it. Tell me if this correct. The KeyDigital scaler will take the 2.35- that is normally has black bars on top and bottom, and will stretch it such that it now fills a 16x9 screen like std 16x9 content would- except that the image will be skewed making everything taller and skinnier. When add an HE lens, this will stretch the image so that it fill a 2.35 screen of the same height but 1/3 wider than my current 16X9 screen.

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stanger89

· #6 · May 21, 2007

Yup, exactly.

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McCall

· #7 · May 21, 2007

another thing is it is recommended that with the lens you use no zoom or as little as possible.

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prismasonic

· #8 · May 22, 2007

Quote:
Originally Posted by uabcar /forum/post/0

Hoping someone can help me calc how large a screen I can have. I'm trying to achieve a somewhat low cost 2.35 add-on to my existing HT. I'm considering the Key Digital HDMI Switcher/Scalar and one of the inexpensive MonoPrice screens. Not sure what to do for lenses yet. My intent is to use my existing fixed mount screen for most viewing and the 2.35 screen for movies shot in that format.

Here are a couple setup details:

- PJ = Sanyo Z5

- PJ Lens in only 9.5 ft from the screen- ceiling mounted PJ (due to room constraints)

- Current fixed mount 16x9 screen is 92" diag. and required about 80-85% of my zoom to achieve

- 2.35 screen would need to be mounted 2-3 inches in front of my current screen making the effective thrown closer to 9.25ft.

Given my short throw, I'm concerned that I may not be able to achieve the screen size I want and therefore it may not be worth the investment. My hope is that I can use the MonoPrice 108" 16x9 to do a 94x40 2.35 screen. I'm just not sure how to go about determining if I can project an image that size. I'm not sure how to calc the impact the lenses will have- and which one's to get.

Can anyone help with the math?

Hi,

This may help you with the math:

http://www.prismasonic.com/english/calculator.php

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