Optoma HD25 - Distance Questions - AVS Forum
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post #1 of 9 Old 06-17-2013, 03:02 PM - Thread Starter
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I'm thinking about getting the HD25, but want to make sure my current setup will work for it.

I have a 120" screen, and the ceiling mount is 16 feet away and about 7 inches down from the ceiling.

According to this calculator:
http://www.projectorcentral.com/Optoma-HD25-projection-calculator.htm

The ideal distance is 14' 3", but my mount is at 16'

My question is, will I be able to adjust the lens/settings to get the HD25 to perfectly fill my 120' screen at 16 feet away?

I know most projectors have the lens zoom/shrink feature, but not sure if that's too far at 16 feet and 7 inches from ceiling.

Thanks!
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post #2 of 9 Old 06-17-2013, 03:32 PM
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Quote:
Originally Posted by Xango View Post

I'm thinking about getting the HD25, but want to make sure my current setup will work for it.

I have a 120" screen, and the ceiling mount is 16 feet away and about 7 inches down from the ceiling.

According to this calculator:
http://www.projectorcentral.com/Optoma-HD25-projection-calculator.htm

The ideal distance is 14' 3", but my mount is at 16'

My question is, will I be able to adjust the lens/settings to get the HD25 to perfectly fill my 120' screen at 16 feet away?

I know most projectors have the lens zoom/shrink feature, but not sure if that's too far at 16 feet and 7 inches from ceiling.

Thanks!

According to the same calculator at 16' throw distance you can shoot to a screen ranging from 122" to 147" diagonal. So "no" it will not work for your 120" screen unless you move it closer by three inches.

The calculator has all the info you needed... you just have to play with the settings a bit.

You can also try the Pro Calculator here:
http://www.projectorcentral.com/Optoma-HD25-projection-calculator-pro.htm

The info you seek is also in the manual linked here:
http://www.projectorcentral.com/pdf/projector_manual_7559.pdf

Unfortunately both the Pro calculator and the manual say, "no" you have to move the projector closer to the screen if you want it to work for your application.

I didn't even address the 7" drop from the ceiling. But that info is useless without knowing how far down from the ceiling your screen is. Look at pages 22-23 of the manual.

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post #3 of 9 Old 06-18-2013, 11:44 AM - Thread Starter
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Originally Posted by walterappleby View Post

According to the same calculator at 16' throw distance you can shoot to a screen ranging from 122" to 147" diagonal. So "no" it will not work for your 120" screen unless you move it closer by three inches.

The calculator has all the info you needed... you just have to play with the settings a bit.

You can also try the Pro Calculator here:
http://www.projectorcentral.com/Optoma-HD25-projection-calculator-pro.htm

The info you seek is also in the manual linked here:
http://www.projectorcentral.com/pdf/projector_manual_7559.pdf

Unfortunately both the Pro calculator and the manual say, "no" you have to move the projector closer to the screen if you want it to work for your application.

I didn't even address the 7" drop from the ceiling. But that info is useless without knowing how far down from the ceiling your screen is. Look at pages 22-23 of the manual.

Hmm, I don't understand the Pro calculator or the Manual info. Especially the offset info.

You mentioned I will need to move it closer by 3 inches. Won't the zoom in/zoom out feature cover the 3 inches? If I don't move it 3 inches, whats the consequence? -Picture will be outside of screen area or too far inside of screen area?

Also, the white part of the screen is 9 1/2 inches from the ceiling, if that helps.
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post #4 of 9 Old 06-18-2013, 01:51 PM
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Quote:
Originally Posted by Xango View Post

Hmm, I don't understand the Pro calculator or the Manual info. Especially the offset info.

You mentioned I will need to move it closer by 3 inches. Won't the zoom in/zoom out feature cover the 3 inches? If I don't move it 3 inches, whats the consequence? -Picture will be outside of screen area or too far inside of screen area?

Also, the white part of the screen is 9 1/2 inches from the ceiling, if that helps.

I'll try and explain in more detail:

Look at the top/side view drawings on page 22 of the manual and the chart at the top of page 23. Find the diagonal image you want the leftmost column of the chart. In this case 120.0"



Columns 8 & 9 show the projection distance range, in feet, that you can use to get a given size diagonal image within the min/max zoom range. For 120" screen you need to be between 13.07 feet (wide zoom) and 15.68 feet (tele zoom). If you were to mount the projector closer than 13.07 feet then you wouldn't be able to zoom OUT enough to get a 120" image. If you were to mount the projector farther back than 15.68 feet then you won't be able to zoom IN enough to make the image fit on your 120" screen. Based on your requirement of a 16 foot throw distance you can't use this projector for that reason. Now if you were to move the projector closer to where it falls within the 13.07-15.68 foot range then it will work (at least from the image size perspective.)

The fixed offset of this projector, (meaning it doesn't have any vertical lens shift capabilities), is unfortunately another deal breaker for you.

Look at the last column of the chart and you will see that the offset is 0.78 feet. This means when the projector is ceiling mounted that the image will be 0.78 feet, (9.36 inches), BELOW the center of the lens. Think of the "Side View" image from the manual being upside down for a ceiling mount to get a visual. You need to add that amount to the distance from your ceiling to the center of the lens to find out how far down the projected image will be from the ceiling. If your projector is already 7 inches from the ceiling, (I'll assume that is the measurement to the center of the lens, if it's a measurement to the top (inverted bottom) of the projector it will make an even bigger difference), then the image will start at 16.36 inches, (9.36 inch offset + 7 inches), below the ceiling, which is well below the 9.5" where you said your screen is mounted.

If you were to get this projector and mount it at 16' back and 7 inches from the ceiling as you desire then the image would be too big and too low to fit on your screen.

Bottom line... if you want to use this projector with a ceiling mount and get 120" diagonal image you will need to move the projector closer to the screen and move the screen down.

Personally, I think you should keep shopping for another projector unless you are willing to make some changes to your room/mounting setup.

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post #5 of 9 Old 06-18-2013, 04:05 PM
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Quote:
Originally Posted by Xango View Post

Hmm, I don't understand the Pro calculator or the Manual info. Especially the offset info.
You really do need to wrap your head around these concepts, even if they are difficult as that is the real world math that is required as a part of projection setup. Zoom ranges, offset, center of lens, etc., are required information for proper projector placement.

Quote:
Originally Posted by Xango View Post

You mentioned I will need to move it closer by 3 inches. Won't the zoom in/zoom out feature cover the 3 inches? If I don't move it 3 inches, whats the consequence? -Picture will be outside of screen area or too far inside of screen area?
How about this...
If you have the camera on your phone, and you want to take a picture of something far away, but they are to small... You zoom the camera in. Right?
Now, you've zoomed the camera in ALL THE WAY - and they are still to small. What do you do?
Do you zoom in more?
No, of course you can't - we've already said you've zoomed in ALL THE WAY.
So, what do you do?
You have to physically move closer!

Same concept here: At 16 feet from the front of the lens to the screen, the SMALLEST IMAGE you can produce is a 122" diagonal. You can use the zoom and make the image as large as 147" diagonal, but no matter what, the image size will be larger than you want. You've used the extents of the zoom and that's all you've got.

SOLUTION: Well, it was mentioned that you could move the projector 3" closer, but this may not be necessary.

Why?

Because you said it is 16' from your screen to the MOUNT.

Is this correct?

If it is indeed 16' (exactly) from the screen to the mount, then the center of the projector will be in the center of the mount at 16', and the lens will be about four or five inches in front of that location. If that's indeed the case, then your lens to screen distance is not 16', but would be 15'7" (about).

At 15'7" from lens to screen you can achieve an image diagonal between 119" and 143". Because 120" is indeed between 119" and 143" that distance is perfectly fine.

Keep in mind it is the lens to screen distance that matters, not the mount to screen distance.
Quote:
Originally Posted by Xango View Post

Also, the white part of the screen is 9 1/2 inches from the ceiling, if that helps.
Your screen starts 9.5" from the ceiling.
Okay, so the center of your projection lens should be at your ceiling height.
9.5" minus 9.36" basically equals your ceiling.

So, as described in the prior post, you would need to move your screen down about 7.5" to get it where it would need to be with this projector for best results.

Also consider: If the mount or lens is off center, you will need to deal with that.

IMO, a person with minimal projector experience needs a projector with a great deal of lens shift and zoom range. This way, you can put the projector on your existing mount, then move the image where it needs to be relatively easily.


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post #6 of 9 Old 06-29-2013, 03:10 AM - Thread Starter
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Originally Posted by AV_Integrated View Post

You really do need to wrap your head around these concepts, even if they are difficult as that is the real world math that is required as a part of projection setup. Zoom ranges, offset, center of lens, etc., are required information for proper projector placement.
How about this...
If you have the camera on your phone, and you want to take a picture of something far away, but they are to small... You zoom the camera in. Right?
Now, you've zoomed the camera in ALL THE WAY - and they are still to small. What do you do?
Do you zoom in more?
No, of course you can't - we've already said you've zoomed in ALL THE WAY.
So, what do you do?
You have to physically move closer!

Same concept here: At 16 feet from the front of the lens to the screen, the SMALLEST IMAGE you can produce is a 122" diagonal. You can use the zoom and make the image as large as 147" diagonal, but no matter what, the image size will be larger than you want. You've used the extents of the zoom and that's all you've got.

SOLUTION: Well, it was mentioned that you could move the projector 3" closer, but this may not be necessary.

Why?

Because you said it is 16' from your screen to the MOUNT.

Is this correct?

If it is indeed 16' (exactly) from the screen to the mount, then the center of the projector will be in the center of the mount at 16', and the lens will be about four or five inches in front of that location. If that's indeed the case, then your lens to screen distance is not 16', but would be 15'7" (about).

At 15'7" from lens to screen you can achieve an image diagonal between 119" and 143". Because 120" is indeed between 119" and 143" that distance is perfectly fine.

Keep in mind it is the lens to screen distance that matters, not the mount to screen distance.
Your screen starts 9.5" from the ceiling.
Okay, so the center of your projection lens should be at your ceiling height.
9.5" minus 9.36" basically equals your ceiling.

So, as described in the prior post, you would need to move your screen down about 7.5" to get it where it would need to be with this projector for best results.

Also consider: If the mount or lens is off center, you will need to deal with that.

IMO, a person with minimal projector experience needs a projector with a great deal of lens shift and zoom range. This way, you can put the projector on your existing mount, then move the image where it needs to be relatively easily.

Thanks for the help guys! It's makes more sense to me now!

It looks like moving the mount forward shouldn't be a problem, if I have to. It's not exactly 16' from the screen, it was actually a bit more, but I should be able to get it within 15 or little more feet.

Moving the screen down shouldn't be a problem either.

The biggest problem it looks like i'm going to have is centering the picture to my screen.
With the lack of left/right shift the HD25 has, I don't think it will be centered based on how much I had to shift my current projector.

Looking into another projector is not an option as the HD25 is my best bet based on price and rating.

My screen mounting screws are in the wall studs, so moving them more left or right isn't really an option. Are there any bracket options to keep the screws where they are in the studs, but actually hang the screen so many inches this way or that way? -Or even the same kind of option for the projector mount?
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post #7 of 9 Old 07-01-2013, 10:27 PM - Thread Starter
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Originally Posted by Xango View Post

Thanks for the help guys! It's makes more sense to me now!

It looks like moving the mount forward shouldn't be a problem, if I have to. It's not exactly 16' from the screen, it was actually a bit more, but I should be able to get it within 15 or little more feet.

Moving the screen down shouldn't be a problem either.

The biggest problem it looks like i'm going to have is centering the picture to my screen.
With the lack of left/right shift the HD25 has, I don't think it will be centered based on how much I had to shift my current projector.

Looking into another projector is not an option as the HD25 is my best bet based on price and rating.

My screen mounting screws are in the wall studs, so moving them more left or right isn't really an option. Are there any bracket options to keep the screws where they are in the studs, but actually hang the screen so many inches this way or that way? -Or even the same kind of option for the projector mount?

Any suggestions / solutions to the above?
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post #8 of 9 Old 07-06-2013, 01:58 AM - Thread Starter
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There must be some kind of option?
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post #9 of 9 Old 07-06-2013, 05:53 AM
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Quote:
Originally Posted by Xango View Post

My screen mounting screws are in the wall studs, so moving them more left or right isn't really an option. Are there any bracket options to keep the screws where they are in the studs, but actually hang the screen so many inches this way or that way? -Or even the same kind of option for the projector mount?

The screen does not have to be mounted to the studs. Any quality heavy-duty drywall anchor will be sufficient to hold up the weight. Just look for anchors with a high shear load rating. Here is an example, there are other types as well.

http://www.strongtie.com/products/anchorsystems/mechanical/sure-wall/#

If you're bound and determined to use the wall studs for support then use a French Cleat which will allow you to slide the screen sideways. Here's an example YouTube video.

http://youtu.be/zP6mP_bApGY

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