Contrast setting that I have during 3D calibration vs 2D calibration - AVS Forum
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post #1 of 18 Old 01-03-2013, 12:48 PM - Thread Starter
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I'm using an X-rite i1Display along with CalMan 5 software, my display is a Panasonic 60GT30. When doing my 2D calibration using the AVS test disc I have a contrast setting of 74, this is the point before I notice clipping. During the 3D calibration I wear the active glasses which are powered on and set my contrast using AVS and my display in forced 3D mode. The point of clipping is around 62. Is this due to the display being put in 3D mode which is brighter? Or is it from the active 3D glasses? Post calibration my 3D looks very good, I don't see an unusual dim picture.

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post #2 of 18 Old 01-03-2013, 02:06 PM
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The 3D modes can be very different than the 2D modes, so it's not unusual at all to have different values for contrast.

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post #3 of 18 Old 01-03-2013, 03:06 PM
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The 3D modes can be very different than the 2D modes, so it's not unusual at all to have different values for contrast.

As someone who has mastered a lot of 3D content I don't agree with this.

There should be no difference, unless the display system is deliberately messing with 'stuff'. which it shouldn't.

Steve

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post #4 of 18 Old 01-03-2013, 03:23 PM
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Originally Posted by Light Illusion View Post

As someone who has mastered a lot of 3D content I don't agree with this.
There should be no difference, unless the display system is deliberately messing with 'stuff'. which it shouldn't.
Steve

What 3D systems are you talking about?

The post is in regards to consumer Panasonic plamas. They definitely have a different mode for 3D with different baseline settings.

If you think I'm wrong, go get some data.

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post #5 of 18 Old 01-03-2013, 03:52 PM
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LOL biggrin.gif

I am stating that there SHOULD be no difference.
All 3D mastering requires no variation in final display set-up.
If there are differences they are incorrect for the source material.
And hence the end results when viewed will be incorrect.
I'm not saying the particular display doesn't have different setting, just that it SHOULDN'T...

Steve

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post #6 of 18 Old 01-03-2013, 03:59 PM
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Originally Posted by Light Illusion View Post

LOL biggrin.gif
I am stating that there SHOULD be no difference.
All 3D mastering requires no variation in final display set-up.
If there are differences they are incorrect for the source material.
And hence the end results when viewed will be incorrect.
I'm not saying the particular display doesn't have different setting, just that it SHOULDN'T...
Steve

I'll ask again what systems are you talking about?

All consumer displays require glasses.
Since glasses aren't simply neutral density filters, you'll need to account for their chromaticity shift. That necessitates having a different calibration profile. Of course you're still mastering for the rec.709 targets, but the calibration of the display to produce an output that measures rec.709 on the other side of the glasses is substantially different. Not to mention all the Plasma's I've seen tweak their panel brightness settings to try and compensate for the fact that active shutter glasses can reduce light output by as much as 80%. Of course shifting panel brightness will also change the maximum contrast number ect...

You'll have to excuse me for trying to give users practical advice they can use in the field.

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post #7 of 18 Old 01-03-2013, 05:38 PM - Thread Starter
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Originally Posted by sotti View Post

I'll ask again what systems are you talking about?
All consumer displays require glasses.
Since glasses aren't simply neutral density filters, you'll need to account for their chromaticity shift. That necessitates having a different calibration profile. Of course you're still mastering for the rec.709 targets, but the calibration of the display to produce an output that measures rec.709 on the other side of the glasses is substantially different. Not to mention all the Plasma's I've seen tweak their panel brightness settings to try and compensate for the fact that active shutter glasses can reduce light output by as much as 80%. Of course shifting panel brightness will also change the maximum contrast number ect...
You'll have to excuse me for trying to give users practical advice they can use in the field.


Thanks for this helpful info that I can understand. I have an additional question, when calibrating gray scale in 3D, how far back from the display should my meter be (with active glasses fixed to it)? I was about about 2ft from screen.

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post #8 of 18 Old 01-03-2013, 06:28 PM
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Originally Posted by ThePrisoner View Post

Thanks for this helpful info that I can understand. I have an additional question, when calibrating gray scale in 3D, how far back from the display should my meter be (with active glasses fixed to it)? I was about about 2ft from screen.

What I would recommend doing is profiling the meter.

Use the reference meter and measure the display with glasses, then for the target meter run, measure without glasses. You can do about 2ft back and for the profiling you may want to us a larger window size.


Then you can measure in contact mode, without the glasses, but get data as if the glasses were in place. But what you are doing should also work, provided the glasses stay in sync.

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post #9 of 18 Old 01-03-2013, 07:12 PM - Thread Starter
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I did use the full field patterns for 3D. 2D I used the window patterns. I kept checking to make sure my glasses were staying in sync and they did. When you say 'profiling the meter', will CalMAN 5 explain this more?

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post #10 of 18 Old 01-03-2013, 08:14 PM
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All consumer displays require glasses.
Since glasses aren't simply neutral density filters, you'll need to account for their chromaticity shift. That necessitates having a different calibration profile. Of course you're still mastering for the rec.709 targets, but the calibration of the display to produce an output that measures rec.709 on the other side of the glasses is substantially different. Not to mention all the Plasma's I've seen tweak their panel brightness settings to try and compensate for the fact that active shutter glasses can reduce light output by as much as 80%. Of course shifting panel brightness will also change the maximum contrast number ect...

Errr, nope...
The calibration profile should have little difference on the 'clipping point' (contrast) as was the original question, wasn't it???
Colour (chromaticity ) is and should be separate.

Steve

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post #11 of 18 Old 01-03-2013, 08:19 PM
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when calibrating gray scale in 3D, how far back from the display should my meter be (with active glasses fixed to it)? I was about about 2ft from screen.

Profiling the meter has nothing to do with the distance from the screen.
The distance should be dictated by the correct patch size for the particular display, as found but using the grey ramp process.
(I am assuming plasma from previous comments - so ABL is the issue here).

When you have the correct patch size then calculate the required distance for the probe in use (viewing angle) and stick to it, regardless if you profile the meter or not.

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post #12 of 18 Old 01-03-2013, 08:45 PM
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Originally Posted by Light Illusion View Post

Profiling the meter has nothing to do with the distance from the screen.

Except that you have to be far enough back to keep your glasses sync'd.

Thanks for the input.

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post #13 of 18 Old 01-03-2013, 11:24 PM
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Originally Posted by Light Illusion View Post

As someone who has mastered a lot of 3D content I don't agree with this.
There should be no difference, unless the display system is deliberately messing with 'stuff'. which it shouldn't.
Steve

So are you saying that the settings you use for contrast, brightness, temp, gamma target in a normal 2D LUT cube calibration should stay the same for a Glasses 3D calibration. Along with meter distance and pattern window size.?

For a lot of us DIY folks that use CM and say a Radiance to do a LUT cube, we only have three window sizes (2%,11% and full screen).
I have suggested to Lumagen that they may want to add a slider for % of window sizes, thereby over riding the 3 choices we have using CM. Or maybe CM can add a slider so we can adjust the window size when using a Radiance.

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post #14 of 18 Old 01-04-2013, 03:25 AM - Thread Starter
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Originally Posted by Light Illusion View Post

When you have the correct patch size then calculate the required distance for the probe in use (viewing angle) and stick to it, regardless if you profile the meter or not.
Steve

Exactly how should I go about accomplishing this? I use the AVS 709 test disc for patterns.

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post #15 of 18 Old 01-04-2013, 06:07 PM
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Quote:
Originally Posted by Light Illusion View Post

Errr, nope...
The calibration profile should have little difference on the 'clipping point' (contrast) as was the original question, wasn't it???
Colour (chromaticity ) is and should be separate.
Steve

3D modes in consumer video displays are typically TOTALLY different than 2D modes. Most of them set Contrast to a very high setting (and if LCD, they set the backlight to a high value, often Maximum) and there can be many other differences between the display's 2D and 3D modes - 3D modes may even have a wider (uncalibrated) gamut because the manufacturer is trying to make the display brighter.

Saying "it shouldn't be different" is like saying you "shouldn't" have to calibrate consumer video displays. In the real world of consumer video displays, the setting the Contrast control clips at (if the display clips at all -- many never clip) is often different in 2D and 3D mode. If the display never clips in 2D mode it typically won't clip in 3D mode either, but there's no guarantee since the manufacturer may change MANY things in the process of trying to make 3D mode satisfyingly bright.

Manufacturers do try (different levels of success, of course) to compensate for the color shift caused by the 3D glasses. That and the changes they make to maximize the light output of the display in 3D mode, make 3D modes quite different to work with than 2D modes. In some cases, 2D and 3D mode are as different as 2 completely different TVs or projectors.

Nobody (that I'm aware of) thinks that 3D discs are mastered to a different standard than 2D... Rec 709 applies to both 2D and 3D modes but all the "non-disc" issues in getting 3D images on consumer video displays often (tempted to say 'always') result in very different calibrations for 2D and 3D modes so that you get the same Rec 709/2.25 Gamma/low error viewing experience for both 2D and 3D modes.

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post #16 of 18 Old 01-05-2013, 05:24 AM
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If you calibrate 3D using the 2D - 3D option, calibration options are fairly limited in the new Sammy plasmas (E7000,8000) because: 1) max output is somewhat limited (to get decent output, contrast/cell light need to be near max for 2D viewing and 3D mode doesn't increase this. 2) you have only 2 point GS adjustments (10 pt is disabled) and 3) " Custom color" is global, so modifications mess up 2D calibration. Looks like black level and 2 pt GS are the only options to improve performance (overall color saturation and Tint/hue appear correct with blue mode and glasses On). BUT: if you watch the Sammy supplied 3D trailers (in it's smartHub(, and check menu options, the Custom Color options appear editable and do not affect 2D settings. I'm not sure, but it seems that calibrating with the limited 2D-3D "forced 3D" mode is probably the only way to go...
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post #17 of 18 Old 01-06-2013, 04:24 AM
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3D modes in consumer video displays are typically TOTALLY different than 2D modes. Most of them set Contrast to a very high setting (and if LCD, they set the backlight to a high value, often Maximum) and there can be many other differences between the display's 2D and 3D modes - 3D modes may even have a wider (uncalibrated) gamut because the manufacturer is trying to make the display brighter.

This is the problem in a nutshell...

Stereo 3D has a much lower target peak white, and cranking up the contrast/brightness to make it 'appear' closer to the 2D brightness is just wrong!
And this has nothing to do with Rec709 Gamut or Gamma.

Ignoring HFR for the moment, in the cinema the 2D peak white is 14 to 16 FtL, while the Stereo 3D peak white is approx 3.5 to 5 FtL.

This is what the Blu-Ray discs are mastered to expect, and with the 3D glasses in the chain is what you should get with the 3D brightness/contract set to the same (roughly) values as for 2D.

Make sense?

Steve

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post #18 of 18 Old 01-06-2013, 03:17 PM
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"should get" and "do get" are not equal in this case.

However, even with panel displays jacking-up brightness for 3D modes, 100% white measurements through activated 3D glasses are still a fraction of what you read without the glasses even when Contrast and/or Backlight settings are much higher than the settings used to achieve 30-35 fL for 100% white in 2D mode. If you do NOT make the display brighter for 3D mode, the dark end of the luminance range can get so dim it's essentially too dark to see any detail.

BTW, the current SMPTE spec for cinema screen brightness is 16 fL +/- 4 fL for 2D.

When I measure 3D home theater projectors I typically measure 2 - 4.5 fL in 3D mode and there's never any trouble getting any of them to 16 fL with the 1.0 gain Stewart StudioTek 100 screen that I use. But achieving 2-4.5 fL requires more light from the projector... simply putting the projector into 3D mode, activating the 3D glasses and doing measurements produces measurements considerably lower than the 2-4.5 fL I end up getting and I have to say... 4.5 fL is MUCH more impressive than 2 fL when viewing 3D content at home. To get more light, all the usual suspect can or are called into play... if there are multiple auto iris modes, using a mode that does not close the iris much helps. If the projector has a fixed iris, opening it either all the way or partially is required. Contrast may be set higher also. And finally, if low lamp mode is used (which is often the case with my 72" wide 1.0 gain screen (viewed from 7.3 feet or 2.9m), the projector may be switched to high lamp mode for 3D.

What's most surprising about 3D, perhaps, is that 4.5 fL for 3D doesn't seem particularly dark when you are used to 16 fL for 2D. Presumably when both eyes see light constantly (even though 1 eye is seeing nothing half the time) our eye-brain system must somehow compensate for the low MEASURED amount of light. On the other hand, the projectors I've used that can't produce more than 2 fL (same 1.0 gain, fairly small screen compared to some) do seem fairly dim and unsatisfying.

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