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Discussion Starter · #1 ·
I've looked at the JVC PDF throw distance versus screen width ( http://www.jvc.com/pro/ntsccatalog/NTSC/Presentation/D-ILAThrow.pdf ) for the G15 projector, and it references "Tele" and "Wide" screen widths. I'm assuming "Tele" is a 4:3 screen aspect ratio, and "Wide" is a 16:9 aspect ratio.


Since the projector itself always projects a 4:3 aspect ratio image (without some type of special lense, right?) why are there two sets of measurements? If you're projecting on to a 16:9 screen that is 100 inches wide, you still need to project a 4:3 rectangle 100 inches wide (of which only the center section is used), right?


I noticed the "Wide" screen widths are listed WIDER than the "Tele" screen widths at the same throw distance. Are these measurements assuming some lense like the ISCO lense on the G15 that stretches the image horozontally, thus giving a wider image at the same throw distance?


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- Dan Butterfield


[This message has been edited by danjb (edited 06-01-2001).]
 

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Dan,


The "Tele" and "Wide" are JVC's notation for the

extremes of the zoom lens. This has nothing to do

with the aspect ratio. The native aspect ratio for

a G15 without an ISCO or a Panamorph is 4:3.


The "Tele" and "Wide" tell you the extremes of the zoom

lens - if you are zoomed in at the "Tele" end of the scale,

the width is one value. If you are zoomed out at the

"Wide" end of the scale, the width is another value, and

the width can take on all values in between as the lens

is zoomed somewhere in between.


Greg

 

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Discussion Starter · #3 ·
Thanks Greg! I was really on the wrong track, and your explanation sure cleared things up. I appreciate it! If I can get the throw distance for the projector high enough such that my screen width is somewhere between the two calculated extreme screen widths (Tele / Wide) for that throw distance, I should be golden, right?


There's no reason, for a given screen width, to try to get the throw distance closer to one or the other of these, is there? Thanks again for any help.


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- Dan Butterfield


[This message has been edited by danjb (edited 06-02-2001).]
 

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Dan,


Correct - for a given throw - the projector can zoom

to any width between the "Tele" and the "Wide" widths

for that throw distance.


I don't believe there is any advantage to any particular

zoom setting. Therefore, for a given screen width,

adjusting the throw distance to give you a particular

zoom setting wouldn't be of any intrinisic value.


Greg
 

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I want to understand this. If I have a 16:9 screen, say 100", how do I calculate throw distance? Throw distance calculations are based on a 4:3 screen. So, my 100" 16:9 screen would be 49.0"h x 87.2"w. I assume in 4:3 mode, the projector will produce an image the same hight (49.0"), but my width will now be reduced to 65.3". So my 4:3 diagonal will now be 81.6". So if my assumption is correct, I guess it is the 81.6" diagonal I use in the throw distance calculation for my 100" 16:9 screen?
 

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Jonmx,


You are correct about the dimensions of the 100" diagonal

screen.


However, if you use a Panamorph, which compresses vertically

then the width will remain constant - not the height.


Without the anamorphic lens - the 4:3 image would by

87.2 X 65.4 and a Panamorph will compress this vertically

to 87.2 X 49.0


If you use an ISCO, which expands horizontally, then the

height remains constant and the width is expanded.


Greg
 

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Jonmx,


The projector doesn't know it's shooting 16:9 when it comes to screen size calculations. Basically it's looking at the maximum screen width for a 4:3 picture. In the case of a 100" wide screen then it would shoot a 75" tall picture.


It's in the scaler where it will scale down the 4:3 picture to fit the middle of the screen, not using the edges of the projector panel. Where as with the 16:9 picture it will use the edges, but not the top and bottom. (not considering anamorphic... that's another discussion) http://www.avsforum.com/ubb/smile.gif




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

Later,


Tony / Premier AV
www.premieraudiovideo.com
 
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