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Old December 15th, 2005, 10:33 PM   #1
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Color Bars and set-up questions

Two very quick questions, I appreciate any advice:

1) There are several color bars that we can find, the FCP bars, the Test Pattern Maker/EchoFire bars, the Blackmagic bars. In your experience, what bars are accurate/correctly calibrated? Which ones should I start to constantly use?

2) I'm mostly editing digital video, from DC25 to DVCPRO50 and soon DVCPRO HD. I will deliver on tapes and/or DVDs. I will not convert anything to analog myself, if something is converted to analog down the road I don't know. The question is, since I am using a JVC monitor with an aditional component card to monitor my video, should I use the color bars with set-up or without set-up? Again, I will finish on digital (that would say NO set-up) but I am monitoring on an analog device (that would say use setup). Plus, when I try to calibrate based on the pluge, with set-up I can see the 3 small black bars and I can easily calibrate, while when I use no set-up everything is black all-over and is harder to differentiate.

Thank you very much for clearing these two questions up!

Take care!
Mike Medavoy is offline   Reply With Quote
Old December 15th, 2005, 11:27 PM   #2
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I don't know whether one set of bars is better than the other, but you definitely don't need to add setup unless you are dubbing to an analog source (and you say that's not a problem for you).

http://www.kenstone.net/fcp_homepage..._nattress.html
http://www.dvinfo.net/conf/showthread.php?t=45073
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Old December 16th, 2005, 12:38 PM   #3
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Hi Mike,

Perhaps this will make a little more sense (or not):

Proper *analog* black level should be at 7.5IRE. (Except in PAL, Japan)
Proper *digital* black level should be at Y'=16 (a luma value of 16). In FCP, this corresponds to 0 on the waveform.

A proper digital to analog conversion will put Y'=16 at 7.5IRE. Some people call this "adding" setup, although I find the term adding to be confusing. It makes a lot more sense if you think of it as converting levels between digital/analog.

The two traps are as follows:
A- Most prosumer, consumer equipment will convert Y'=16 to 0 IRE instead.
If you have an all digital workflow (ingest and output digital), then you can get away with simply calibrating your monitor to bars from your EDITING system.
B- Some cameras can apply "fake" setup, where they raise the DIGITAL levels being recorded. This way, it'll look like the camera is performing a proper digital-analog conversion. You should generally avoid this unless you know what you're doing, and you know how this is useful.
This raised digital black level is not proper black level.

Quote:
1) There are several color bars that we can find, the FCP bars, the Test Pattern Maker/EchoFire bars, the Blackmagic bars. In your experience, what bars are accurate/correctly calibrated? Which ones should I start to constantly use?
I recommend you use the FCP bars, as it is:
A- Accurate. If you are importing bars, each editing program may convert the levels differently. FCP imports RGB differently depending on whether or not the project is superwhite.
B- does have the blacker than black PLUGE bar (the leftmost one). You don't see it on the waveform, but it's there. To check, simply crank the "brightness" control on your monitor.


2- If you're using a Blackmagic card, perhaps it has a setting which allows the card to convert proper digital black level to 7.5 IRE instead of 0? This should be a little better if your broadcast monitor has other input sources with black level at 7.5IRE (i.e. a DVD player).
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Old December 17th, 2005, 12:07 PM   #4
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Thanks very much for claryfing everything...

Two quick questions regarding color bars, since I am now re-calibrating my monitor using FCP bars and no set-up. Regarding the pluge:

- We alter brightness until the middle bar disappears into the left one, I got that. But what about the right bar... We stop right when the middle bar "disppears" and the right bar is very distinct, or we continue further until the right bar becomes barely visible? It makes a difference, and it usually takes 4-5 more brightness "units" to go down. I'm asking because in all the articles on calibration is says the right bar should be barely visible, but if we stop when the middle bar disappears, the right bar is very very visible.

- about the contrast, it seems it is something not very objective, just to watch the white reference square and appreciate if it's too white, or bleeding into the other dark squares, etc etc. Not too bright and not too dark is something very subjective. Is there a more precise way to insure accurate contrast?

Thanks a lot!
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Old December 17th, 2005, 12:49 PM   #5
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Quote:
- We alter brightness until the middle bar disappears into the left one, I got that. But what about the right bar... We stop right when the middle bar "disppears" and the right bar is very distinct, or we continue further until the right bar becomes barely visible? It makes a difference, and it usually takes 4-5 more brightness "units" to go down. I'm asking because in all the articles on calibration is says the right bar should be barely visible, but if we stop when the middle bar disappears, the right bar is very very visible.
I would stop when the middle bar disappears.

Why: It's nice to be able to see what's barely above black level. There's a bunch of 'steps'/levels between the middle and rightmost PLUGE bars.

Quote:
- about the contrast, it seems it is something not very objective, just to watch the white reference square and appreciate if it's too white, or bleeding into the other dark squares, etc etc. Not too bright and not too dark is something very subjective. Is there a more precise way to insure accurate contrast?
I believe SMPTE RP 166 calls for 30 or 35fL (I think it is 35 foot lamberts). Very few people follow that, so it may not actually make sense to follow it.

Here's an alternative approach:
Increase contrast up all the way to the point where you just get image distortion, and then back off slightly so there's no distortion. When you drive a CRT too much, two forms of distortion can happen:
A- Geometric distortion. Lines aren't as straight, or they are in a different position on screen.
B- The electron gun begins to lose focus.
To spot distortion, you can take a piece of paper and let static stick it to the monitor face. Position the paper so you just see a sliver of the left side of the 100 IRE / 100% white PLUGE bar. Turn contrast (should really be called "white level") all the way down beforehand.

Now you also need to pay attention to the brightness level surrounding the monitor. If it's too brights, some of the whites on your monitor will appear grey. Lower room brightness, or make a compromise and increase the contrast on the monitor.

If the monitor looks blinding to you, then that'll probably give you eye strain. Raise room illumination, or lower the monitor brightness.

SMPTE RP 166 calls for the surround/wall illumination to be 10% of the monitor illumination. I think that would correspond to about 37.7 IRE (or 35 on FCP's waveform). The wall color should also be D65 (or neutral gray, reflecting D65 light).

Few people actually follow SMPTE RP 166, so I wouldn't sweat it. The main thing is to understand what happens, where your monitor is inaccurate and how the surround affects your perception of things on the monitor.
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Old August 5th, 2012, 12:47 PM   #6
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Re: Color Bars and set-up questions

So, if I may ask a related question (that I hope is quick)...

My client shoots using 5 Canon XL2s. They send signal out via analog BNC. When hooked up into a waveform monitor, should I see a setup level at 7.5%? Or does the XL2 record digitally and, though it is being sent out analog, display at 0?

I am using a, be it old, Leader 525 line 5872 WFM.
David Hentz is offline   Reply
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