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km987654
Joined: 25 Jul 2007
Posts: 2874
Location: Australia
TV/Projector: Barco BG809s
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| Posted: Tue Mar 03, 2009 10:34 am Post subject: Image brightness changes with resolution |
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I am running a DVD through a Lumagen Vision scaler via a composite video connection to port 5 on my Barco. If I display a 720p picture it is bright if I change to 1080i/50 or any variation from /50 up the image becomes very dull. My PJ is a barco 1100 that is fitted with 75mhz neck boards.
Can anyone offer any suggestions.
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secstate
Joined: 20 Mar 2006
Posts: 720
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| Posted: Tue Mar 03, 2009 2:08 pm Post subject: |
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Are you sure the contrast/brightness setting are the same for each memory block? They are stored for each memory block so maybe 1080i has lower settings enabled. I know this is sort of obvious but it doesn't hurt to ask.
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km987654
Joined: 25 Jul 2007
Posts: 2874
Location: Australia
TV/Projector: Barco BG809s
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| Posted: Tue Mar 03, 2009 9:34 pm Post subject: |
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I will check it again tonight but as I recall the contrast and brightness were adjusted to the same level 60%. I should give you some detail here. There appears to be horizontal dark banding on 1080i as well as the darker general image. These dark bands do not appear at 720p. I know that the 75mhz RGB Output boards had some issues with banding and streaking is this simply from that type of amp??
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Mark_A_W
Joined: 15 Mar 2006
Posts: 3068
Location: Sunny Melbourne Australia
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| Posted: Tue Mar 03, 2009 10:12 pm Post subject: |
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Sounds like it doesn't like the timing and isn't clamping black properly.
Can you fiddle with the timings on the lumagen at all? I'd be playing with sync widths and back porches.
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secstate
Joined: 20 Mar 2006
Posts: 720
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| Posted: Tue Mar 03, 2009 10:17 pm Post subject: |
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| km987654 wrote: | | I will check it again tonight but as I recall the contrast and brightness were adjusted to the same level 60%. I should give you some detail here. There appears to be horizontal dark banding on 1080i as well as the darker general image. These dark bands do not appear at 720p. I know that the 75mhz RGB Output boards had some issues with banding and streaking is this simply from that type of amp?? |
The streaking caused by those boards, at least what I have seen and what has been reported is brighter not darker. Also in addition to playing with timings, you are forcing negative sync right? Barco's can do strange things when they aren't getting negative sync. Some resolutions will be fine without negative sync and others will act strangely if displayed at all.
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km987654
Joined: 25 Jul 2007
Posts: 2874
Location: Australia
TV/Projector: Barco BG809s
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| Posted: Tue Mar 03, 2009 11:30 pm Post subject: |
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I have some checking to do. I took it that the lumigan was useing negative sync but have never checked. I will now though. I will check on timings as well.
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Elaine Benes
Joined: 25 Apr 2006
Posts: 1416
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| Posted: Wed Mar 04, 2009 1:10 am Post subject: |
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On a Marquee it would be beneficial to check your horizontal Phase to see if the actual image is properly centered. It's been so long I can't remember if a Barco acts the same way, but I believe it may. Look for a horizontal image shift control that moves the image inside the raster...
Also, the higher vertical resolution of 720p actually uses more phosphor, although the difference is likely less dramatic than you are seeing. When CRT's were still being produced new, the light output ratings were almost always done at some super high resolution to light up the most possible phosphor, even though practically no one ever actually used those resolutions. It provided the manufacturers with bragging rights though...kinda like the "peak" wattage output ratings of amps...
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km987654
Joined: 25 Jul 2007
Posts: 2874
Location: Australia
TV/Projector: Barco BG809s
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| Posted: Wed Mar 04, 2009 9:21 am Post subject: |
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Just checking the instructions on the lumigan and it would appear that sync and timing can be adjusted. The instructions say negative sync is default though. I need to print these instructions they are too hard to read on a computer.
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km987654
Joined: 25 Jul 2007
Posts: 2874
Location: Australia
TV/Projector: Barco BG809s
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| Posted: Sat Mar 07, 2009 9:20 pm Post subject: |
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I have checked the sync is negative and it is. When people talk about timing I imagine they are talking about Horizontal Sync Pulse Width and if this is the case then I have tried the entire range with no effect at 1080i. This problem only seems to exit at 1080i. I tried 840p last night and it looks good.
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Sat Mar 07, 2009 9:47 pm Post subject: |
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Not familiar with your projector but does it have a setting for clamp?
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km987654
Joined: 25 Jul 2007
Posts: 2874
Location: Australia
TV/Projector: Barco BG809s
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| Posted: Sun Mar 08, 2009 3:04 am Post subject: |
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| macgyver655 wrote: | | Not familiar with your projector but does it have a setting for clamp? |
I am using a Lumigan Vision scaler. Can't see any clamping setting.
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Sun Mar 08, 2009 3:32 am Post subject: |
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The clamping setting would be in the projector if it has it.
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km987654
Joined: 25 Jul 2007
Posts: 2874
Location: Australia
TV/Projector: Barco BG809s
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| Posted: Sun Mar 08, 2009 4:18 am Post subject: |
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Can't see clamping mentioned anywhere in the projector documentation.
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