HD MONITOR CALIBRATION with SMPTE and ARIB Bars

If you're in a hurry, just watch Guy Cochran's great how to video on this topic >>>

This post is in regards to HD monitor calibration only. There are several issues related to standard definition video and monitors that do not apply to HD at all:

1. Setup: In NTSC analog "setup" is added, lifting the entire signal so that the blackest black in the picture is placed at 7.5 IRE. This is an old throwback from when broadcasters switched from Black and White to Color. The entire picture information had to be slightly lifted to leave ample room for the color sync portion of the signal. Setup is completely irrelevant in the digital realm (see my post on Legacy Baggage). In both digital SD and HD, blacks are recorded at 0 IRE and in digital broadcast, no setup is added. So why do some HD cameras have the option to add setup to their picture? I don't know but it's a horrible idea. When your HD production inevitably gets broadcast in SD, setup will be automatically added. That means if you already artificially added setup to your digital image, your blacks are now going to be broadcast at a very milky 15 IRE. Not a good look. Keep those blacks at 0.

2. Phase: There is no "Phase" control for digital HD monitoring. Only a CHROMA saturation control affects the picture. Phase as it relates to monitors is an analog issue only. However if you send Component HD, which is analog, to some older monitors you may have to adjust the phase control as well.

Monitors, Monitors, Monitors

These days, there are lots flavors of HD displays – LCD, plasma, CRT, and now OLED. Each has its pros and cons but calibrating each type to display an accurate image is exactly the same. Generally, video engineers prefer CRT’s because of their ability to reproduce a true black (what’s known as "tube blacks") and they have a forgiving viewing angle. These monitors are extremely vulnerable to ambient light though so a dark tent is really the best place for critical viewing. LCD's on the other hand, especially the Panasonic BT-LH1700, are very popular because they're more cost effective and portable. Compared to CRT's however, they have a lot of shortcomings particularly in their ability to reproduce a true black. Recently though, on the new Panasonic 17"s - the 1710 and 1760 - the contrast ratio has been significantly improved and the black level is more faithful. On the horizon, brand new OLED (Organic LED) technology offers a very promising solution to overcoming the known issues with LCD’s. Marshall just announced a new line of OLED monitors that look very very cool. We’ll see what happens with that.

So how do you set up a monitor? Your camera generates a color bars test signal - either a traditional SMPTE version or the newer, fancier Japanese HD version, ARIB. If you're a Sony XDCAM EX user, you're used to looking at ARIB bars. The ubiquitous SMPTE bars look exactly like their standard definition version but they are actually a little bit different. If you plugged your analog Betacam SP into a waveform and turned the color bars on you would see that the Test Pluge, those 3 little gray bars in the lower right corner, read differently than they would if sent from a HD camera. On analog systems, the left bar is 3.5 IRE, the middle is 7.5, and the right one is 11.5. This is to account for setup so that you can set your monitor blacks at the level that they will be broadcast. On the HD version of SMPTE bars, the left pluge is -3.5 IRE, middle is 0 IRE, and right is 3.5 IRE. Here are SMPTE color bars sent from a Panasonic HDX900 and the corresponding waveform.





Notice on the waveform that the colors in the test pattern are at 75 IRE or 75% saturation. The peak white square at the bottom is at 100 IRE or 100% white. As you can see this test signal is designed to help you set the brightness, contrast, and chroma on your monitor so that what you are seeing on the picture display as is close to the recorded signal as possible.

MONITOR CALIBRATION WITH HD SMPTE BARS:

1 ADJUST BRIGHTNESS - 2 ADJUST CONTRAST - 3 ADJUST COLOR

-Turn the monitor on and let it warm up for a bit. This is especially important if it’s a CRT. Turn the lights in the room off or way way down so as not to get ambient light pollution. Watch out for stray reflections hitting the monitor.
-Plug the camera into the monitor via HD-SDI or Analog Component. We need a HD image here, not down converted SD. SDI and component are essentially the exact same signal, merely 2 different ways of relaying it. If you’re monitoring HD, make sure that your camera is sending out HD video and not a down converted signal. Turn on the camera's color bars.

1. Adjust the brightness by setting the PLUGE – the little gray bars. Because monitors display LUMINANCE and then COLOR, I always calibrate the luminance first. Where you set your brightness and contrast will also affect your color saturation so it's a good idea to adjust this before adjusting the chroma display.

-Set the brightness to the mid point.
-Turn the chroma all the way down if that helps you to see the values better. It is easier to evaluate luminance on a monochrome display.
-Among the 3 PLUGE bars, the left one is- 3.5 IRE, the middle is 0, and the right one is 3.5. The goal here is to adjust the monitor brightness (black level) until you can only barely see the right hand bar. By doing this, you’re telling the monitor to display black at the same level it's being recorded: 0 IRE.

2. Now that you have set the monitor’s black level by adjusting the brightness, set the white level by adjusting the contrast. This is by far the trickiest and most subjective setting. If you have the ability to put your monitor in Monochrome, this is very helpful. If you don't have it - Starting at the mid point, turn the contrast up until the white square on the bottom of the signal stops responding. Once it stops responding, you’ve exceeded peak white. So now you back it off until you start to see it responding again, i.e., turning from white to gray. Now turn it up to the point where it turned white and won’t get any whiter. There you go. Now whites are white.

-If you do have a monochrome display feature, you should be looking at something like this:


This is too bright for HD Acquisition:


It really should look more like this:


3. Now that the luminance levels have been set it’s time to set the Chroma. Those of us who from the SD Analog world are used to adjusting the phase and saturation to achieve this. In HD, phase does not exist. Phase is an analog thing and in HD there is only the chroma saturation adjustment to arrive at properly calibrated colors. You must have a BLUE ONLY or BLUE GUN feature to do this correctly. Some cameras can send 75% saturation bars or 100% saturation bars. The colors in both the SMPTE and ARIB test patterns are 75% saturated so thats what you should use to display colors that are faithful to the recorded signal.

-Turn the BLUE ONLY on.
-Adjust the chroma level until the color bars and test bars beneath them are a SOLID value.

You should be looking at something like this:


Definitely not like this:


There you have it. That’s the standard way to calibrate a HD monitor.




MONITOR CALIBRATION WITH ARIB BARS:

1 ADJUST BRIGHTNESS - 2 ADJUST CONTRAST - 3 ADJUST COLOR

For those who aren't familiar, this is an ARIB bar:


Here's an explanation of what you're looking at:


-First off, you'll notice that this is essentially the exact same process as for HD SMPTE Bars.
-Turn the monitor on and let it warm up for a bit. This is especially important if it’s a CRT. Turn the lights in the room off or way way down so as not to get ambient light pollution. Watch out for stray reflections hitting the monitor.
-Plug the camera into the monitor via HD-SDI or Analog Component. We need a HD image here, not down converted SD. SDI and component are essentially the exact same signal, merely 2 different ways of relaying it. If you’re monitoring HD, make sure that your camera is sending out HD video and not a down converted signal. Turn on the camera's color bars.

1. Just like SMPTE bars, start calibration with the LUMINANCE.

-Set the contrast to the mid point.
-Turn the chroma all the way down if that helps you to see the values better.
-Now looking at this PLUGE you can see that it’s a bit different than the SMPTE version. These 3 gray bars are surrounded by pure 0 IRE black. The left hand bar is -2 IRE, the middle is 2 IRE, and the right hand bar is 4 IRE. Adjust the brightness until the middle bar (2 IRE) is barely visible. If you can just see the middle and right bars, your blacks should be perfectly set.

2. Now that you have set the monitor’s black level by adjusting the brightness, set the white level by adjusting the contrast.

-Now that you have set the monitor’s black level by adjusting the brightness, set the white level by adjusting the contrast. This is by far the trickiest and most subjective setting. If you have the ability to put your monitor in Monochrome, this is very helpful. If you don't have it - Starting at the mid point, turn the contrast up until the white square on the bottom of the signal stops responding. Once it stops responding, you’ve exceeded peak white. So now you back it off until you start to see it responding again, i.e., turning from white to gray. Now turn it back up to the point where it turned white and won’t get any whiter. There you go. Now whites are white.

It should look like this:


3. Time for the CHROMA. As I mentioned earlier, in digital HD, phase does not apply.

-Turn on the BLUE ONLY
-This is quite a bit different than SMPTE. Adjust the chroma until the 3 light bars blend with the long, solid strip beneath it.

It should look like this:


And back again to the final result - this is where you need to be:


ADDENDUM 04/23/09: 75% COLOR BARS VS. 100% COLOR BARS

Some cameras have the ability to generate both 75% and 100% Color Bars. The "%" in this case refers to the percent of color saturation - The colors bars in the 75% Test Signal are at 75% of the 100% possible color saturation in the SMPTE HD standard. Both of the color bar test patterns explained above are 75% saturation. All HD cameras have the ability to capture 100% of the SMPTE color gamut. 75% vs. 100% is just a test signal and has nothing to do with the colors you are recording. Two cameras that are set up identically but one is generating 100% color bars and the other is generating 75% color bars are both recording the exact same signal. As for calibrating a HD monitor to 100% bars and what is the advantage or disadvantage? Both the ARIB and HD SMPTE Color Bar Test Patterns are 75% saturation. The correct way to arrive at a calibrated display is to line it up the 75% saturated colors. IF the color bars in HD SMPTE or ARIB test pattern were 100% saturated and you used the same method as described above to calibrate, the colors displayed would not be true to the recorded signal. Fortunately for me, you, and everyone else - this isn't an issue because the default color bars generated by just about any HD camera are 75% saturation.

Here are standard SMPTE HD 75% Color Bars:


And seen on a Vectorscope (set at 100% saturation):


Here is a SMPTE 100% Color Field (in my experience, it's better to calibrate your monitor using either of the Color Bar Test Patterns illustrated above as opposed to this Color Field):

In the HD realm, this is the only test pattern I've encountered that has 100% color saturation.

And here it is on the Vectorscope:


Here's what the correctly displayed 100% Test Pattern looks like on Blue Only (notice anything similar? The equal and alternating values are the tell all for correct calibration):