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dturco
Joined: 06 Feb 2009
Posts: 3778
Location: Eastern Shore Maryland
TV/Projector: Runco DLP VX-3000i Marquee 9500 parts doner
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| Posted: Mon Nov 01, 2010 6:26 pm Post subject: How do you adjust contrast on V-2 full H/D? |
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Ok so I was trying to adjust the gamma screw and by mistake turned the Contrast screw. I think I counted the right amount of turns and put it back where I started, but you never really know.
The Marquee's picture looks great. The Brite control is set at 48 and the contrast is at 60. I just want to be sure. I have a digital multimeter Crafstman something or other 3 years old. No scope or anything fancy.
So how do you measure the contrast Pot for the correct voltage?
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Ron W
Joined: 07 Aug 2009
Posts: 860
Location: Mississauga
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| Posted: Tue Nov 02, 2010 5:01 pm Post subject: Re: How do you adjust contrast on V-2 full H/D? |
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| dturco wrote: | Ok so I was trying to adjust the gamma screw and by mistake turned the Contrast screw. I think I counted the right amount of turns and put it back where I started, but you never really know.
The Marquee's picture looks great. The Brite control is set at 48 and the contrast is at 60. I just want to be sure. I have a digital multimeter Crafstman something or other 3 years old. No scope or anything fancy.
So how do you measure the contrast Pot for the correct voltage? |
There is really no "correct voltage" as such which is basically just another term for "white point" on your display. The Moome converter's contrast pot just gives you a little finer adjustment, within a relatively small parameter, of that particular picture control. If your whites are not over saturated or blooming and the picture looks great to you, that is all that matters.
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dturco
Joined: 06 Feb 2009
Posts: 3778
Location: Eastern Shore Maryland
TV/Projector: Runco DLP VX-3000i Marquee 9500 parts doner
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| Posted: Tue Nov 02, 2010 5:30 pm Post subject: |
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Thanks Ron,
I went back and put in the DVE disc and Get Gray disc, adjusted the pic till the white Bloomed then turn it back a bit and , well it looks great so, it will be staying where it is.
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Firefly rules. Can't stop the signal.
http://www.hulu.com/firefly
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betel
Joined: 20 Apr 2006
Posts: 448
Location: Maryville, Tennessee (Just South of Knoxville)
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| Posted: Mon Feb 28, 2011 6:25 pm Post subject: Re: How do you adjust contrast on V-2 full H/D? |
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| Ron W wrote: | | dturco wrote: | Ok so I was trying to adjust the gamma screw and by mistake turned the Contrast screw. I think I counted the right amount of turns and put it back where I started, but you never really know.
The Marquee's picture looks great. The Brite control is set at 48 and the contrast is at 60. I just want to be sure. I have a digital multimeter Crafstman something or other 3 years old. No scope or anything fancy.
So how do you measure the contrast Pot for the correct voltage? |
There is really no "correct voltage" as such which is basically just another term for "white point" on your display. The Moome converter's contrast pot just gives you a little finer adjustment, within a relatively small parameter, of that particular picture control. If your whites are not over saturated or blooming and the picture looks great to you, that is all that matters. |
Moome gives a very pricise value for this at 0.7V so it makes me think its value is not arbitrary. I notice on my G90 the 100% ire from the DVE disc is not nearly as bright as the internal full white when I press the gain button. Makes me think the Moome is limiting the contrast so I'd like to check it. If the user shouldn't turn the contrast screw it would be nice if it had a plug in it. It is very easy to turn by mistake. Anyone know where to measure the voltage at?
Just found this quote from Moome concerning contrast adjustment:
"please clockwise at least 25turn until hear tiny click noise on the pot. then unclockwise the pot 4 turn~
thanks"
Later in the thread the voltage is given as .7Vpp. Since multimeters measure in rms you will need an osciliscope to see the peaks. Also the .7Vpp is measured at the card output (I assume measuring each one of the rgb pins to ground should read the same).
Last edited by betel on Mon Feb 28, 2011 6:51 pm; edited 1 time in total
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Nashou66
Joined: 12 Jan 2007
Posts: 16171
Location: West Seneca NY
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CIR Engineering
Joined: 25 Aug 2008
Posts: 4269
Location: Chicago USA & Berlin Germany
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| Posted: Mon Feb 28, 2011 7:50 pm Post subject: |
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There is absolutely a correct adjustment for contrast and it is in no, way, shape, or form arbitrary. For almost all video standards, the voltage for analog HD video is 0.7 volts peak to peak (pp). For some situations the voltage is specked at 1.0 volts pp.
For our projectors 0.7 volts is what should be used. If you use a higher voltage than 0.7 volts pp you will hurt the gamma response. If you go too high you will clip whiter than white and eventually start clipping detail off the top end because the video chain inside the projector can only accept voltages below 1.0 volts pp (or sometimes just 0.7 vpp). If you go above the correct voltages all details will start to get lost at progressively lower IRE levels as you increase the voltage. First details will be lost at 90IRE and above, than 80 IRE and above... The voltage between 0.7 and 1.0 is supposed to be there for overhead and wtw.
If you go too low on the contrast, the light output from the projector will suffer and your gamma response will be wrong.
With an external box like the Moome v2 you can get the voltage off any of the RGB cables, but you really should always use green. What you do on an external is connect one end of a 75 ohm resistor to the green signal and the other end of the resistor gets plugged into your o-scope. Apply a 100 IRE window to the HDMI input on the EXT box and then adjust the contrast pot such that the 100 IRE window shows 0.7 volts from black to white (pp) on the scope.
For an internal HDMI to RGB converter you just put your probe on the green pin, apply 100 IRE window, and measure the pp voltage on the o-scope screen.
This is very important as voltage variations from 0.7 by as little as 0.1 volts are quite deleterious to the final image.
Regards,
craigr
_________________
JETI 1501-HiRes 2nm Spectroradiometer
JETI 1211 Spectroradiometer
Photo Research PR-650 Spectroradiometer
Klein K10-A Colorimeter
Murideo Fresco SIX-G HDMI 2.x Multimedia Generator
Murideo Fresco SIX-A HDMI 2.x Analyzer
Light Illusion ColourSpace XPT Color Calibration Software
Light Illusion LightSpace XPT Pro Version 10.x Color Calibration Software
OMARDRIS JVC Software Patch to use K10-A and Jeti with JVC OEM AutoCal Software!
Sencore CR7000 CRT Tube Analyzer / Rejuvenater
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www.CIR-Engineering.com - craigr@cir-engineering.com
Phone: 865-405-6892
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Nashou66
Joined: 12 Jan 2007
Posts: 16171
Location: West Seneca NY
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overclkr
Joined: 08 Mar 2006
Posts: 4227
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| Posted: Tue Mar 01, 2011 12:01 am Post subject: |
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| Nashou66 wrote: | Awesome explanation Craig!!!
Athanasios |
Yep. Dude is smart 
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mp20748
Joined: 12 Sep 2006
Posts: 5689
Location: Maryland
TV/Projector: 9500LC Ultra / Super 02 and 03 VIM
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| Posted: Tue Mar 01, 2011 4:19 am Post subject: |
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| CIR Engineering wrote: | There is absolutely a correct adjustment for contrast and it is in no, way, shape, or form arbitrary. For almost all video standards, the voltage for analog HD video is 0.7 volts peak to peak (pp). For some situations the voltage is specked at 1.0 volts pp.
For our projectors 0.7 volts is what should be used. If you use a higher voltage than 0.7 volts pp you will hurt the gamma response. If you go too high you will clip whiter than white and eventually start clipping detail off the top end because the video chain inside the projector can only accept voltages below 1.0 volts pp (or sometimes just 0.7 vpp). If you go above the correct voltages all details will start to get lost at progressively lower IRE levels as you increase the voltage. First details will be lost at 90IRE and above, than 80 IRE and above... The voltage between 0.7 and 1.0 is supposed to be there for overhead and wtw.
If you go too low on the contrast, the light output from the projector will suffer and your gamma response will be wrong.
With an external box like the Moome v2 you can get the voltage off any of the RGB cables, but you really should always use green. What you do on an external is connect one end of a 75 ohm resistor to the green signal and the other end of the resistor gets plugged into your o-scope. Apply a 100 IRE window to the HDMI input on the EXT box and then adjust the contrast pot such that the 100 IRE window shows 0.7 volts from black to white (pp) on the scope.
For an internal HDMI to RGB converter you just put your probe on the green pin, apply 100 IRE window, and measure the pp voltage on the o-scope screen.
This is very important as voltage variations from 0.7 by as little as 0.1 volts are quite deleterious to the final image.
Regards,
craigr |
Yep, dude is without doubt an EXPERT in what he does. And that's why one should understand these deeper things in electronics today, to properly setup and calibrate for the best image.
And for anyone wanting the BEST image possible from their setup, Craig would be the person to get. No one else has invested the time and $$ as he has to understand the HD signal chains that also deals with digital to analog conversion from HDMI sources.
HDMI with it's complex color space issues require a certain expertise. And that expertise is one that usually require special attention to matching the source device to the video chain. Craig has mastered this. And because of his deep knowledge and understanding of today's digital to analog conversion devices, it explains why he travels with the gear he uses.
There are Calibrators, and then there's a Master Calibrator....you'll know him when he shows up, he'll be heavily equipped to professionally calibrate not only your PJ, but your entire video chain along with your precious PJ.
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overclkr
Joined: 08 Mar 2006
Posts: 4227
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| Posted: Tue Mar 01, 2011 4:40 am Post subject: |
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| mp20748 wrote: | | CIR Engineering wrote: | There is absolutely a correct adjustment for contrast and it is in no, way, shape, or form arbitrary. For almost all video standards, the voltage for analog HD video is 0.7 volts peak to peak (pp). For some situations the voltage is specked at 1.0 volts pp.
For our projectors 0.7 volts is what should be used. If you use a higher voltage than 0.7 volts pp you will hurt the gamma response. If you go too high you will clip whiter than white and eventually start clipping detail off the top end because the video chain inside the projector can only accept voltages below 1.0 volts pp (or sometimes just 0.7 vpp). If you go above the correct voltages all details will start to get lost at progressively lower IRE levels as you increase the voltage. First details will be lost at 90IRE and above, than 80 IRE and above... The voltage between 0.7 and 1.0 is supposed to be there for overhead and wtw.
If you go too low on the contrast, the light output from the projector will suffer and your gamma response will be wrong.
With an external box like the Moome v2 you can get the voltage off any of the RGB cables, but you really should always use green. What you do on an external is connect one end of a 75 ohm resistor to the green signal and the other end of the resistor gets plugged into your o-scope. Apply a 100 IRE window to the HDMI input on the EXT box and then adjust the contrast pot such that the 100 IRE window shows 0.7 volts from black to white (pp) on the scope.
For an internal HDMI to RGB converter you just put your probe on the green pin, apply 100 IRE window, and measure the pp voltage on the o-scope screen.
This is very important as voltage variations from 0.7 by as little as 0.1 volts are quite deleterious to the final image.
Regards,
craigr |
Yep, dude is without doubt an EXPERT in what he does. And that's why one should understand these deeper things in electronics today, to properly setup and calibrate for the best image.
And for anyone wanting the BEST image possible from their setup, Craig would be the person to get. No one else has invested the time and $$ as he has to understand the HD signal chains that also deals with digital to analog conversion from HDMI sources.
HDMI with it's complex color space issues require a certain expertise. And that expertise is one that usually require special attention to matching the source device to the video chain. Craig has mastered this. And because of his deep knowledge and understanding of today's digital to analog conversion devices, it explains why he travels with the gear he uses.
There are Calibrators, and then there's a Master Calibrator....you'll know him when he shows up, he'll be heavily equipped to professionally calibrate not only your PJ, but your entire video chain along with your precious PJ. |
100% Agreed BIG DOG
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CIR Engineering
Joined: 25 Aug 2008
Posts: 4269
Location: Chicago USA & Berlin Germany
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| Posted: Tue Mar 01, 2011 2:03 pm Post subject: |
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You guys are making me blush 
Much appreciated though...
Kind regards,
craigr
_________________
JETI 1501-HiRes 2nm Spectroradiometer
JETI 1211 Spectroradiometer
Photo Research PR-650 Spectroradiometer
Klein K10-A Colorimeter
Murideo Fresco SIX-G HDMI 2.x Multimedia Generator
Murideo Fresco SIX-A HDMI 2.x Analyzer
Light Illusion ColourSpace XPT Color Calibration Software
Light Illusion LightSpace XPT Pro Version 10.x Color Calibration Software
OMARDRIS JVC Software Patch to use K10-A and Jeti with JVC OEM AutoCal Software!
Sencore CR7000 CRT Tube Analyzer / Rejuvenater
Authorized Dealer for Lumagen & just about everything worth buying
www.CIR-Engineering.com - craigr@cir-engineering.com
Phone: 865-405-6892
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