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Old October 28th, 2007, 04:54 PM   #1
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SMPTE color bars

Hi,

I am trying to calibrate my JVC CRT monitor via Premiere and /or my Canon XH/A1. The SMPTE bars, both the camera and Premiere use, do not have the three black pluge bars, only the light grey. Does anyone know where I can download an accurate SMPTE test chart or provide advice on how to get the best results from the two I have. I am fully familiar with the technnique of adjusting the colours - but it would help if I had the correct test chart.
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Old October 28th, 2007, 06:23 PM   #2
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Vincent

Are these any use? From Vegas.

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SMPTE color bars-bars_pal.jpg   SMPTE color bars-bars_ntsc.jpg  

SMPTE color bars-bars_pluge.jpg  
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Old October 28th, 2007, 06:49 PM   #3
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Thank you Ian, I will give them a shot.

Since posting the thread I discovered that the Canon does put out the three pluge bars. They show up on my LCD computer screen but not on my JVC monitor, I have tried adjusting brightness and contrast but can't see them.

Thank you for your time and screens
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Old October 28th, 2007, 08:50 PM   #4
 
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Funny thing about pluge bars when run thru computer video codecs. Some codecs work ONLY in NTSC RGB, ie 15-235 IRE. If you've processed a colorbar pattern thru one of these codecs, it could clip the information sufficiently for you to never see all 3 pluge bars.
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Old October 28th, 2007, 09:22 PM   #5
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Proper color bars are generated in Y'CbCr color space. You can have difficulty getting the right Y'CbCr values from an R'G'B' image, especially since there are different mappings from R'G'B' to Y'CbCr values (Quicktime color management, studio RGB versus computer RGB are issues). Because of this, I would really avoid using color bars from R'G'B' images since the resulting bars are likely to be incorrect. (Which will happen if you download those images into Premiere; those values are appropriate for Vegas if using Vegas' DV codec).

2- It might be that the Canon camera clips values that are below black level??? Some DVD players do this. Maybe your camera is doing that.

In that case... an alternate test pattern would be to superimpose a moving chip that is just barely brighter than black level. Adjust black level until you cannot see that moving chip. The Avia calibration DVD has an example of this.

Or just adjust black level until you can just barely see the rightmost chip in the PLUGE bars.

2b- Or use a different DV camera for monitoring.

3- Bill... I think you are using the wrong units.
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Old October 28th, 2007, 11:58 PM   #6
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Try this for the pluge signal.....

http://www.mivs.com/technical/colorbars.html
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Old October 29th, 2007, 12:13 AM   #7
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The other issue to watch out for is that your DV camera may not output the same levels as other devices... especially due to most DV devices putting black level at 0 IRE when they should really put it at 7.5 IRE.

You can use the color bars from your NLE.
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Old October 29th, 2007, 12:54 AM   #8
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Thank you all for your replies

The reason this concerned me so much is, I have just finished a DVD production and was viewing the first master disc on a Sony Bravia LCD TV. The production is a user guide to the Nikon D40X camera, and the studio shots of the camera were far too dark, yet my JVD CRT monitor was showing it as correct (perhaps a touch darker than I would like). Of course I would trust my CRT monitor rather than the LCD TV, but this does concern me as most people are going to view the DVD on either a TV or computer LCD screen. I just need the master to look right before I have the final discs printed.
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Old October 30th, 2007, 01:08 AM   #9
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If I'm stuck in a situation where I don't have well adjusted CRT's to adjust to- (I had my reference monitor ripped off recently, so right now that is fairly often.)-I will double check by taking a DVD of my edited master down to a retail electronics store and check it out there.

It's great for a reality check anyway, as almost no viewers are going to watch on color critical CRT's unless you're submitting for broadcast. In a retail store, the varying pictures you inevitibaly run into will give you a good idea of what your viewers will be experiencing. If you are filming camera gear with details in black on black, this might help a bit.
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Old November 1st, 2007, 11:38 PM   #10
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Quote:
Originally Posted by Vincent Oliver View Post
Hi, I am trying to calibrate my JVC CRT monitor via Premiere and /or my Canon XH/A1.
Never a good idea - use a dedicated video signal generator instead! All TV repair shops have them.
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