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Using meters to set up monitors


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#1 Bob Hayes

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Posted 22 June 2006 - 02:04 PM

Does anyone have any experience using meters to set up HD monitors. Using my Sekonic meter I read the white square on the camera sent color bars and it read 18 Foot Candles. Using my color meter the Green/Magenta was 0, the color temp was 5600. Is there a way to use these tools to standardize my setting op of a field monitor?

This was a properly set up monitor.
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#2 Laurent Andrieux

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Posted 22 June 2006 - 03:07 PM

First of all, I noticed bad phenomenoms when approaching a meter from a tube monitor due to its magnetic field : the monitor's colors turn bad whereby I've stand the meter.

Second I'd rather think of a spotmeter reading on the white bar, better than an incident reading...

third, I'm not sure a normal color meter should work on a tube monitor, since there are special ones for metering them, but what do I know ? Why not

4th a monitor is supposed to display a higher temperture, typically 6500 K. I know it sounds weird, anybody knows why ? I think it's because TV engineers made the statment that people are supposed to watch TV - as an average situation - by daytime in the shade (of their home) what do you think ?

Maybe HD Field monitors are supposed to display 5600 K ? Problem is, if your field monitor is 5600, but the image is supposed to be broadcast on a 6500 monitor/video projector, your image will then be bluish when broadcast...
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#3 Michael Nash

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Posted 22 June 2006 - 03:09 PM

Does anyone have any experience using meters to set up HD monitors. Using my Sekonic meter I read the white square on the camera sent color bars and it read 18 Foot Candles. Using my color meter the Green/Magenta was 0, the color temp was 5600. Is there a way to use these tools to standardize my setting op of a field monitor?

This was a properly set up monitor.


I've never tried it that way, but I think there might be too many variables to rely on that technique. The biggest one being that no two monitors are exactly the same in terms of brightness and gamma, so you'd have a hard time trying to force a good image "by the numbers," at least in the field. Reflections on CRT glass and vieweing angle of LCD's could create problems, too.

Maybe engineers use similar tools when setting up monitors in the shop, but I've never seen this approach in the field. What I usually end up doing is just "getting to know" the monitor I'm using, and double-checking my work on another monitor whenever possible. And of course a waveform is your ultimate reference for signal brightness. Even calibrated, professional monitors can sometimes disagree with each other, so you learn to "interpret" the monitor's performance with a waveform reference.

The color temperature meter is a good idea though. When possible I like to check the color gain and bias of a monitor by turning the chroma off ("off," not "blue only") and looking at color bars, and see that the gray scale is indeed "gray" throughout, and not "brown" or "pale blue" or some mixture throughout. Some monitors (depending on the technology) allow you to adjust the gain (white) and bias (mids) of the three color channels (sometimes "level" and "gamma"), but this should really be done by an engineer with proper tools for accuracy.
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#4 Bob Hayes

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Posted 23 June 2006 - 11:53 AM

I've never tried it that way, but I think there might be too many variables to rely on that technique. The biggest one being that no two monitors are exactly the same in terms of brightness and gamma, so you'd have a hard time trying to force a good image "by the numbers," at least in the field.


Although matching multiple monitors is great, I just want to standardize how I get my DIT monitor to spec.. I thought this was going to work but now I don?t know. I was in a post house color correction bay yesterday and decided to test my theory. I used my color temp meter. One monitor was 5,500 and another in another bay was 5,650 and it seemed pretty accurate. Checking the Kelvin seemed to work. But when I checked the Green/Magenta it fluctuated between -2 and +2. It just depended on how I held the meter and when I hit the button. The foot candles fluctuated between 15 FC and 30 FC. Again based on when I hit the button. I feel like my idea of using a Minolta Color Meter and a Seconic Light meter to calibrate monitors is not going to work.
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#5 Laurent Andrieux

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Posted 23 June 2006 - 03:53 PM

Yep... see, I think the screen frequency is a parameter... I used to do reflection meterings with a spotmeter, you never get the same value, when you press the button so that you have to make averages... Not precise at all...
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#6 Michael Nash

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Posted 24 June 2006 - 01:28 AM

Okay, I took a look at the book "High Definition and 24P Cinematography" today for some insight. I don't have the book here, so this is from memory.

Obviously some meters can't deal with flickering subjects like monitors. The Sekonic L-508 cine (which I use) can. There is a Spectra model mentioned as well. Using the Sekonic with the dome retracted, placed flat against the the 100% white patch on the screen, it should read 54 fc. It's a different number for the Spectra.

Check out the book for more info:

http://www.amazon.co...5Fencoding=UTF8
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#7 Bob Hayes

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Posted 27 June 2006 - 09:00 PM

With much joy and excitement I tried my Sekonic ball retracted and found a range pf 15 FC to 30 FC depending on when I pressed the button. Drat!
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#8 John Pytlak RIP

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Posted 28 June 2006 - 12:21 PM

Kodak Display Manager System:

http://www.kodak.com...s....4.24&lc=en

http://www.kodak.com...1_userguide.pdf

Your spot meter and color meter may not be properly calibrated for certain displays (they emit discontinous spectra and may have a refresh rate), but can be used to maintain a display luminance and white point color temperature once you have calibrated a particular monitor.
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#9 Patrick Neary

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Posted 28 June 2006 - 12:57 PM

Hi All-

I've got the Wheeler books here- he sez the SMPTE white square should read 27fc with a cinemeter-II or 54fc with an L508. I tried this once with an old Sekonic 398, figuring it should work too, but like Laurent's experience, the monitor screen freaked out when I put the flat disc up to the screen, and that was the end of that.
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#10 Laurent Andrieux

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Posted 28 June 2006 - 02:37 PM

white square should read 27fc with a cinemeter-II or 54fc with an L508


I don't like that much, BTW, the fact that different meters should give different values...
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#11 Michael Nash

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Posted 28 June 2006 - 05:04 PM

I don't like that much, BTW, the fact that different meters should give different values...


Well this is common with trying to read discontinuous sources like monitors, and why I don't like using a spot meter to expose TV and computer screens. You can't always trust the reading (until you learn by trial that you can rely on your particular meter). And you can't really trust your eye, either. ;)

I remember Geoff Boyle had a whole thread about this on CML some time back:
http://www.cinematog...B/tvscreens.htm
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#12 Laurent Andrieux

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Posted 28 June 2006 - 08:43 PM

Thanks for the link, Michael !
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#13 Bob Hayes

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Posted 28 June 2006 - 09:17 PM

Success! My good old Spectra consistently read 64 FC when placed against the white chip on the colors bars. No fluctuation. I removed the dome and all slides. My Minolta color temp seems fairly accurate with a -1 Magenta to +2 Magenta fluctuation. I?m still testing this. Not that my own skills and eye aren't absolutely dead on but I'm looking at $400,000 dollars worth of equipment delivering a picture that I am eye balling the contrast and Hue. Hmmm.
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#14 Hal Smith

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Posted 28 June 2006 - 10:22 PM

Success! My good old Spectra consistently read 64 FC when placed against the white chip on the colors bars.

Which old Spectra?
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