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Discussion Starter · #1 ·
Ok, why am i getting different sizes when I input different but same ratio signals? When I input 1080i pass through from a Zenith 1080 box I get a picture that fills the screen from my throw distance perfectly with a nice sized image on the raster. When I switch it to 720p it will not fit the image on the screen even at 100% hsize sizing. Its about two to three inches short all around. My DVD player through a Quadscan Elite at 720p fills it well but without any overscan. 960p from the Quadscan will fill it with about two percent overscan. What gives?


Now I dont get why the sizes change but all this likely goes back to the throw distance for my setup (I'm guessing now). I originally had it located right where the Barco Lens program said i should but i ended up moving it about three inches closer. Now I'm thinking I should move it back but it initially concerned me because I was shrinking the HSize so much before? Maybe i should stop paying attention to the what the scale says. Further help with raster and image sizing would be appreciated. I've already consumed the search engine to death recently and am exhausted with this stuff. I have problems with the Guy Kwo post because little of what is described is particular to a Barco 808's control system.


For what its worth its a 92" wide 16:9 screen.


Thanks, Brian
 

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Different memories are being used due to different scanning rates.

I bet your convergence is even more wierd than your screen sizes. You have to re-calibrate the projector for each scanning rate you ever input. If you go into the menus when in each of the inputs selected you will see that the projector is using a different memory bank to setup the projector. It is a real pain in the neck, hours of setup for each different source, but it is worth it.


Larry
 

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Sorry, I didn't fully read your post. My answer is pretty irrelivent to your problem. I don't know the real answer.


Larry
 

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The pros recommend sending in each input format while the projector is still on the ground on a table. Find out which one has the smallest image on screen, and adjust throw distance to fit that image. Then when you mount the projector, you can decrease the h-size of the other images. (Note that while doing this, you may want to check raster use area and make sure it is maximized for the smallest image before declaring it the smallest image.)


I think the reason the image size changes as input signal changes has to do with the way the projector's deflection units handle that signal. There is also the issue of the porches being sent from one device are not going to be the same time as those sent by another, resulting in perhaps a wider (due to longer porches) blank area around an image from one device than another.


960p at 16:9 AR may be too much for the 808. Have you checked that you aren't getting overlapped scan lines? Most with the 808 in 16:9 use 720p it seems.
 

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Discussion Starter · #5 ·
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960p at 16:9 AR may be too much for the 808. Have you checked that you aren't getting overlapped scan lines? Most with the 808 in 16:9 use 720p it seems.
I am currently comparing the two to see which is sharpest. The person I bought it from was using 960p and it was setup that way by Terry F so that's the way I started but last night I was gravitating to 720p. I could see scanlines up close but not at seating position.


Quote:
Then when you mount the projector, you can decrease the h-size of the other images. (Note that while doing this, you may want to check raster use area and make sure it is maximized for the smallest image before declaring it the smallest image.)
I am not following you here. ????


Thanks for the help, Brian


P.S. what was really confusing me was that 720 p from DVD source fit perfectly while it did not from my hidef box. I might try Source 3 to compare, i know 4/5 are somewhat finicky.
 

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Discussion Starter · #6 ·
BTW, how do you set it up not to be anamorphic? Brian
 

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Sorry, I wasn't being very clear, was I. Not to mention throwing words I shouldn't use (like images). :)


After you find the proper throw distance for the source which produces the smallest image with your raster and image areas optimized for maximum light output (but still staying in the safe zone), you will need to recheck each of the other sources. Every single one of them will be too wide now, extending into the unsafe zone. Turn down contrast (to prevent tube damage if you will be taking a while to do this) and use the h-size control to reduce the width of these other sources to fit your screen.


If you used 50 (midposition) for the h-size setting when selecting the throw distance with your smallest source, you should still have enough adjustment room left to decrease h-size and get your other sources to fit on screen. If not, adjust throw distance and retry the smallest source with a larger h-size.


Getting throw distance right is perhaps the hardest part, and its even harder here for you with so many different sources having different timings (and thus producing radically different outputs).


The fact your hidef box gives you a "good" 720p while the DVD player doesn't just goes to show you how much the timings generated by the device controls how the image will be displayed. Next year when you upgrade your DVD player, you may be going through the whole thing again, only finding this time that the image is too large and you can't make it small enough. :D


Welcome to the dark side!
 

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Brian,

I didn't read everybodys cpmments above so if I am repeating what someone else wrote sorry.

Usually the highest frequency will give you the least amout of H width. So in your case 960P would be the least, 720P wider and 1080i would be the widest for a given H width setting. Obviously you want to size the picture for each of these inputs as they will all go into seperate memories. So in setting these things up and to insure you have enough throw distance, input your highest frequency (960P) and make sure that you have enough G width to fill your screen with H width opened up.

Let's see to answer your other question on anamorphic, set up the windows desktop so that it fills your screen, and anamorphic will take care of itself, as will 4:3. You may have to do some setting in your aspect ratio of your software DVD player.


Terry
 

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Discussion Starter · #9 ·
Thanks for the input guys.

Quote:
After you find the proper throw distance for the source which produces the smallest image with your raster and image areas optimized for maximum light output
Ok, the interchangeable use of image and raster is one of the things that has confused me to death on this forum. There is no way to change the raster size short of some adjustments on the boards right? And I never see anybody talk about that. What you mean is the image area optimized for maximum light output on the raster not raster and image areas adjusted right? Or am i missing something.


Thanks again, Brian
 

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Heh. Raster and image confused me for a while too.


Raster strictly means the area the electron beam scans over. The image cannot exist outside of the raster, as the electron beam will never go outside of the raster.


You can see the raster by setting contrast down very low (just about 0), cranking brightness up to 50+, and looking into the lenses. Usually you can see the scan lines, and the difference in brightness between the image and the raster that it is contained in. Play with the contrast and brightness while doing this (and while feeding a video signal), it can be quite educational. :D


The image area cannot be controlled from the projector, only the raster. When you adjust the image size controls (vertical and horizontal) through the software (aka with the remote) you are actually adjusting the raster, despite whatever the menus state. The only exception is the h-phase control. This controls the left/right position of the image within the raster and can be useful to help recenter a slightly off-center source.


When you move the image around on screen, via any controls, including convergence controls, you are actually adjusting the raster. That the image is affected is just a side effect. :D


The image size / location within the raster is controlled by the source(s). When the source sends the image, it sends pulses to denote where the image exists within a larger timing frame. The larger timing frame is the raster. The blank area around the image within the raster is denoted by the porches, which exist to allow the electron gun time to retrace (reposition) between scan lines and frames.


Board adjustments can be used to affect the raster size/position, but its not recommended that you play with them, unless you are a skilled tech for that machine, or really think you know what you are doing. :D The software controls exist and are usually enough.


My poorly phrased comment about optimizing for light output was written at work, so I apologize for not explaining myself better. What I was trying to do was suggest that you maximize the size of the raster on the CRT faces, but keep it within the safe zone. (Leave around 1/8" all the way around, including at the corners, between the raster edge and the CRT face edge.) The more CRT face you use, the brighter the image will be (at lower contrast settings).
 
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