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Discussion Starter · #1 ·
Question #1 – objective

I would like to build the video for my HT around a Sanyo PLC-XP21N projector. My room configuration requires a throw distance from lens to screen of 14.5 feet and a viewing distance of approximately 13 feet. If it helps to visualize the room, the projector will be ceiling mounted in a 3-foot wide by 2.5-foot deep alcove that used to contain a fireplace on the back wall. The seating are will be directly in front and to the sides of the projector. The projector cannot be placed closer to the screen because the room has a high ceiling everywhere other than the alcove.


Using the projector calculator at ProjectorCentral.com, I find that my minimum 4:3 screen size is:

Diagonal: 97.7 inches

Width: 78.16

Height: 58.62


Although I will be viewing both 4:3 and 16:9 (and other) material, I would prefer to use a 16:9 screen. Which of the dimensions from the 4:3 calculation must be preserved to avoid projecting over the edges of the screen?


Since the 97.7 inch 4:3 screen would use the projector’s full zoom capacity, I am concerned that in 16:9, the image will be so large as to be unusable for my viewing distance.



Question #2 – objective

Are screen size calculations affected by scaling the image using an HTPC or Quadscan? How about a Panamorph lens?



Question #3 – subjective

The rule of thumb I have seen to determine screen size is:


Viewing distance >= (2 x screen width)


Assume that the answer to #1 comes up that, given my throw distance, my minimum screen width is 7.5 feet or more. Remember, I cannot extend my viewing distance. I know this is subjective and depends partly on the projector, but what are some opinions about whether this should be a “deal killer†for my project?


Thank you for the help.


Randy Howie

 

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Randy:

I didn't look at projector central, but it sounds like you're saying that with a 14.5' throw, the minimum screen width would be 78.16 inches, or roughly 6.5 feet. Correct?


To answer your first question, since a 4x3 screen is taller relative to the width than a 16x9, you would use a 16x9 screen of the same width as the 4x3, but not as high. To do the math, 78.16*9/16=43.965. So, your height would be about 44 inches.


To answer question 2, no, neither the scaler or the Panamorph would change the screen size with a 16x9 screen. The scaler only changes your choices for the resolution of the image - the number of horizontal and vertical dots displayed per inch, but not the size of the screen itself. The Panamorph will take the native 4x3 screen produced by the projector, and turn it into 16x9. So, it wouldn't change the size of a 16x9 screen you could use. However, if you ever did want to display 4x3 images, and you were using a 4x3 screen, you could show a larger display without the panamorph. That's with a 4x3 screen, so it doesn't affect you.


Question 3 - distance vs. width. You say your minimum is 7.5 feet. Isn't 6.5? (78.8 inches)? That should be fine with your viewing distance of 13 feet. Many people on this forum prefer much larger screens, some are at 1 times screen width! So, you should be fine there.


Hope this helps!


- Dave
 

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Discussion Starter · #3 ·
Thanks for the reply. I think I need some follow-up:


You said:

> To answer your first question, since a 4x3 screen is taller relative to the width than a 16x9, you would use a 16x9 screen of the same width as the 4x3, but not as high. To do the math, 78.16*9/16=43.965. So, your height would be about 44 inches. <


I think you are saying that I could use a 78.16 x 43.965 screen. It seems that would work for 16:9 material, but when I project 4:3, wouldn't I be overshooting the screen on the top and bottom because I am below the minimum vertical size the projector can throw from 14.5 feet (58.62 inches)? It seems like your calculation would leave me with no pillars on the left and right of the 4:3, but I would loose image at the top and bottom. Is that right?


Maybe I am making this more difficult than it needs to be. I hope so. Let me show you my calculation, and maybe someone can tell me where I am going wrong.


Minimum 4:3 image per ProjectorCentral.com:


Width: 78.16

Height: 58.62

Diagonal: 97.70


If I want to project both 4:3 and 16:9 onto a 16:9 screen, I think I would have to maintain the height dimension and adjust the width to 16:9.


Width: 104.21 (8.7 feet!)

Height: 58.62

Diagonal: 119.57


I hope someone can point out the error in my calculation. Isn't a 10 foot diagonal too large for a viewing distance of 13 feet (for all but the greatest die-hards)?


I would love an answer to my original question, but maybe I should expand this to ask for opinions on using a 4:3 vs. 16:9 screen if you plan to project both formats (although DVD movies is the highest priority). Maybe a 4:3 screen would solve this problem.


Any further clarification would be appreciated.


Thanks.


Randy

 

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Randy....I have the same question, but the way I understand it is that it works just like your 4:3 TV set. When you view 16:9 material, the width stays the same, but the hight is reduced accordingly. Anyways I hope someone confirms this.


BTW, I plan on getting the Sanyo PLV-XP18N myself and my house is being framed right now. What made you pick the -XP21N over the -XP18N? From my limited reading, the extra brightness really isn't useful for hometheater unless you really have a lot of ambiant light and many people on this forum seem to think the pixelation isn't any better contrary to what www.projectorcentral.com says. The only thing I am waiting on to see if the PLV-60 offers a better solution, but the early reviews have me leaning towards sticking with the -XP18N.


Jon Mohney
 

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Quote:
Originally posted by randyhow:


I think you are saying that I could use a 78.16 x 43.965 screen. It seems that would work for 16:9 material, but when I project 4:3, wouldn't I be overshooting the screen on the top and bottom because I am below the minimum vertical size the projector can throw from 14.5 feet (58.62 inches)?
Perhaps something like the iScan Pro could be used. It has a 'squeeze' mode that keeps 4:3 material the same height as 16:9 display and puts bars at the sides without needing to zoom. The only drawback is you would be loosing even more light because you still have the top and bottom chopped off (from 16:9) and now you are lobbing off the sides too.

However, I think that any scaler solution will result in that if you can not zoom enough to get the 4:3 to fit vertically.


All of these AR issues are why I stuck with a 4:3 screen. I just use top and bottom masking and can keep the width the same regardless of AR and never have to mess with the zoom.




[This message has been edited by Mark Lopez (edited 06-03-2001).]
 

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Randy:

Ok, I think I see where you're coming from now. Are you talking about zooming in to watch 4x3 and zooming out to watch 16x9? If so, then your calculations are right. That would work if the projector could zoom out all the way to fill the full width of the 104 inch wide 16x9 screen. So, that would give you a viewing distance of about 1.5 screen widths. A bit close to me, but many people go even closer. It's all up to your personal preference.


What I was talking about was using an HTPC or scaler to display the 4x3 image inside the 16x9 screen. This is what myself and many other people do. The disadvantage of this is that you can't use the full 4x3 resolution of the projector when displaying 4x3. I don't know your projector, but if it's say, 800x600, then you'd get 640x480 worth of 4x3 resolution inside the 16x9 screen.


- Dave
 

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Another rule of thumb to consider is the height of the screen to viewing distance ratio. I personally never recommend my customers sit any closer than 3 to 4 times the height of the screen. The width is usually not a consideration if you follow this ratio where both 16/9 and 4/3 will be used on the same screen. In your projector's case, you will have to get a 4/3 screen because your projector is a 1024 x 768 (4/3) panel. And since you will watch both 4/3 and 16/9 material, I would use the 4/3 height measurements as the worst case scenario...ie.. If you purchased a 100 in diagonal screen that = 60 (h)inches by 80(w) inches. 60 inches x 3 = 180 inches 0r 15feet which according to your rooms distance of 13 ft means too BIG!. Now some will disagree with my formula, but if you are going to have friends over remember...Not everyone likes feeling like they are sitting in the front row of the movie theater...

Now of course this same screen and projector in 16/9 mode change things.The 60inch height will shrink approx 20% or to roughly 48inchs (4 ft) x 3 equals 12ft...

which is close to your limit of 13ft. My 2cents is go with the 80inch 4/3 screen.
 

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Discussion Starter · #8 ·
Thanks for all of the input.


The 80 x 60 (100 inch diagonal) 4:3 option with horizontal masking is sounding pretty good. That will create a 80 x 45 (91.79 inch diagonal) image for 16:9 material. This size seems appropriate for my room and will not put me at the absolute zoom limit of the projector.


Does anyone want to make a case for a 16:9 screen?
 

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"The only drawback is you would be loosing even more light because you still have the top and bottom chopped off (from 16:9) and now you are lobbing off the sides too."


Yes, total displayed lumens is reduced, but the brightness of the image is the same. The image gets smaller, but not dimmer.


------------------

Noah
 

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It's the mix of material that you plan on watching with the projector that should decide the aspect ratio of the screen. If you plan on watching lots of DVDs or at some point HDTV on the big screen,then 16x9 is the way to go.


Standard def TV looks pretty crappy in comparison to either HTPC based DVD or HDTV on a big screen, so I still do the majority of my normal TV viewing with a 27 inch direct view.


It's fairly common to initially prefer 4:3 since its the aspect ratio we all grew up with, but 16x9 is the aspect ratio of the future and will be a better long term solution especially with DVD or HDTV being projected.


It's also worth noting that there are anamoprhic conversion lenses that are tailer made for home theater applications. Using one of these lenses makes the choice of a wider screen the best possible solution to future proof you purchase.
 
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