Contrast doesn't produce ideal white. - AVS Forum
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post #1 of 15 Old 01-25-2014, 08:37 PM - Thread Starter
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Hi. I have a Samsung UN40EH6030. I'm using Disney WOW. Source is a PS3 RGB Full, superwhite on or PS4 RGB Full, YCBCR Full. Since I got the PS4 I decided to revisit my settings.

Using the disc to set Brightness I get ideal black at 44. Max contrast does not produce ideal white. However, when I mess with Brightness I get Ideal white at 66. Anything I can do or should I just set Brightness at 55 as a compromise?
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post #2 of 15 Old 01-26-2014, 07:33 AM
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For the PS4, I recommend using RGB Limited and YCbCr Limited (though for the latter Full is no different, so that setting is meaningless). Set HDMI Black Level to Low on the TV.


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post #3 of 15 Old 01-26-2014, 05:24 PM
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The real issue here is that discs of test patterns will NEVER tell you what the RIGHT Contrast setting is. All they will tell you is the highest setting you can use that does not clip white. Which in itself is a fairly trivial thing since there's no image detail in white above the 235 video level (you should be using 16-235 / limited range when working with consumer video displays versus computer monitors where you may want to use full-range 0-255 video depending on how the monitor works...if the "monitor" is just a lightly modified consumer display, it might still work better in 16-235 mode).

Those discs do tend to make you think they are going to help you find the RIGHT setting for Contrast but that is absolutely positively NOT TRUE. To find the RIGHT setting for the contrast control you have 2 choices.

Before you set Contrast it will be useful to know the usable adjustment range (which may not be the full adjustment range the manufacturer offers), the disc can be useful for that.

If you have a colorimeter and calibration software, you measure the light level of 100% white. If you are in a completely dark room, you will probably want 30-35 fL for 100% white. You cannot achieve that without a meter and software to measure the display. For a room with a low level of light in it, you probably want 35-40 fL of light. If the room is brightly lit (like daylight coming in), you might want 55-65 fL or even more.

If you do NOT have a colorimeter and calibraton software, all you can go by to determine the RIGHT contrast setting is whether or not you notice eyestrain after 2-3 hours of viewing the screen. If you do NOT detect any fatigue around your temples and eyes after 2-3 hours you are either darker than optimum or right close to the recommended levels mentioned above.

If you find it is always difficult to escape eyestrain, and if you want to improve your perception of how black the blacks are on your video display, you'd be an ideal candidate for a color-balanced (i.e. D65 which is NOT the same thing a 6500K color temperature...you can have 6500K that is NOT D65 and possibly not even remotely close to D65) bias light behind the video display.

Eyestrain comes from the black/dark area surrounding a bright video display screen... your eye "sees" the black and tries to open your irises, but you immediately "see" the bright video display again and your brain tries to close your irises. So there's a constant battle in your head over what your irises should be doing... open, close, open, close.... that's what leads to the feeling of eyestrain after 2-3 hours. You want to eliminate that constant battle and the only way to do that is to get the white level set correctly. Without a colorimeter, all you can do is guess at what the right Contrast setting is by noticing whether you are experiencing eyestrain after a period of use. If you are, you can turn down the luminance of the video display until the eyestrain feeling stops. Or you can add a bias light which should allow the display to be brighter without eyestrain. Of you get a meter and KNOW you are using a decent light level -- and some still find that they just can't eliminate the feeling of eyestrain even with 30 fL in a dark room, so those are great candidates for bias lighting behind the video display.

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post #4 of 15 Old 01-28-2014, 12:44 AM
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Quote:
Originally Posted by Doug Blackburn View Post

If you have a colorimeter and calibration software, you measure the light level of 100% white.
For a plasma, what pattern would be used for that? window? if so, what size? or maybe ANSI contrast pattern?
Quote:
Originally Posted by Doug Blackburn View Post

If you are in a completely dark room, you will probably want 30-35 fL for 100% white. You cannot achieve that without a meter and software to measure the display. For a room with a low level of light in it, you probably want 35-40 fL of light. If the room is brightly lit (like daylight coming in), you might want 55-65 fL or even more.
So it is clearly a relation between the ambient light in the room and the needed/wanted fL for 100% white on the display.
Given that, shouldn't it be possible to measure the ambient light and then calculate the right amount of light output needed from the display?

Edit: I found a discussion about it here: http://www.avsforum.com/t/1343528/is-this-a-cheap-alternative-to-the-ideal-lume/30#post_20674786
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post #5 of 15 Old 01-28-2014, 04:38 AM
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Quote:
Originally Posted by rickardl View Post

For a plasma, what pattern would be used for that? window? if so, what size? or maybe ANSI contrast pattern?
So it is clearly a relation between the ambient light in the room and the needed/wanted fL for 100% white on the display.
Given that, shouldn't it be possible to measure the ambient light and then calculate the right amount of light output needed from the display?

Edit: I found a discussion about it here: http://www.avsforum.com/t/1343528/is-this-a-cheap-alternative-to-the-ideal-lume/30#post_20674786

for plasma you can use small APL from AVSHD709, 10% APL or 10% windows from GCD, APL or windows from GCD

for measuring 100% white, choose the 100% white pattern in your disc, continuous reading and look at the Y measure
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post #6 of 15 Old 01-28-2014, 05:26 AM
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I get very ragged and unpredictable results with AVSHD small APL on my ST60....I think GCD 10% APL patterns are better since they seem to trigger or force the APL logic to work in the same manner at each stimulus level...

Sent from my ALCATEL ONE TOUCH 6030X using Tapatalk
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post #7 of 15 Old 01-28-2014, 07:35 AM
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Quote:
Originally Posted by mytbyte View Post

I get very ragged and unpredictable results with AVSHD small APL on my ST60....I think GCD 10% APL patterns are better since they seem to trigger or force the APL logic to work in the same manner at each stimulus level...

Sent from my ALCATEL ONE TOUCH 6030X using Tapatalk

try small standard windows (non-APL)... like 5% to 7.5% or so


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post #8 of 15 Old 01-28-2014, 07:58 AM
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Quote:
Originally Posted by rickardl View Post

For a plasma, what pattern would be used for that? window? if so, what size? or maybe ANSI contrast pattern?
So it is clearly a relation between the ambient light in the room and the needed/wanted fL for 100% white on the display.
Given that, shouldn't it be possible to measure the ambient light and then calculate the right amount of light output needed from the display?

Edit: I found a discussion about it here: http://www.avsforum.com/t/1343528/is-this-a-cheap-alternative-to-the-ideal-lume/30#post_20674786


I still use window patterns where the window is about 10% of the area of the screen and surrounded by black. There's a lot of recent hysteria about avoiding all effects of automatic brightness limiting by using either very small window patterns (which are problematic for some meters to read accurately (depends on meter design) and constant Average Picture Level (APL) that maintain the same light output for all windowed patterns. IMO, the plasma TV will never operate without brightness limiting so the calibration should include SOME brightness limiting to help keep images accurate. You can always re-measure gamma with APL patterns to see if it is horrible or not.... if it is not horrible after using "tradiaional" 10%-size windows, you're good to go.

Some software supports subtracting ambient light from meter readings, but ambient light... daylight especially, changes constantly as the sun moves across the sky, as clouds come and go, as leaves on nearby trees appear, change size, change color, and fall again, as sun reflects from nearby buildings at different times of day, etc. If it is only artificial light you are worried about, there's more of a chance of a software's ambient light cancellation working but you'd have to test it to see how it works with your specific meter since meters all work differently and all respond to ambient light differently - mostly influenced by the angle of view of the meter, how close the meter is to the flat panel (obviously, for a projector calibration, ambient light has to be off completely), and how the meter "sits" against the panel.

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post #9 of 15 Old 01-28-2014, 12:24 PM
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Quote:
Originally Posted by Doug Blackburn View Post

If it is only artificial light you are worried about, there's more of a chance of a software's ambient light cancellation working but you'd have to test it to see how it works with your specific meter since meters all work differently and all respond to ambient light differently - mostly influenced by the angle of view of the meter, how close the meter is to the flat panel (obviously, for a projector calibration, ambient light has to be off completely), and how the meter "sits" against the panel.
I got an i1Display Pro. And yes, it was artificial light I was thinking of and I thought about aiming ithe meter at the wall above the TV. And using that reading for 10-15%(?) for what the display needs to output but that might be too simple to work? biggrin.gif
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post #10 of 15 Old 01-28-2014, 02:51 PM
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That definitely won't work because even if the wall is nominally white, it's unlikely to be D65 white. If you use ANY color other than D65 as the reference, all your measurements will be off by the amount the wall is not perfectly D65 (i.e. xy coordinates of .3127 and .329) but in the opposite direction because the software will be mis-directing you due to the wall not being a true D65 source. You are calibrating the TV to D65 so your only accurate "source" for a measurement is a true D65 reference.

Software that supports ambient light correction will have you make readings off the TV with and without the light in the room and it will then calculate the differences in the readings and turn that into a correction factor, but you still have to make the environment around the meter completely dark (sometimes done with blankets or something similar to block the ambient light during the reference measurement phase.

But again, this procedure only works when the meter has a fairly narrow angle of view or a "protected" view (like a suction cup that blocks outside light around the sensor. If your meter has a wide angle of view so that direct light can be detected around the sides of the meter, the correction process isn't likely to produce very good results. So it would just be better to calibrate in a dark room and avoid the light issue altogether unless you know what your meter "sees". If you were to do the ambient light correction thing (and again, for it to be done right, the software program you use would have to support it) you would have to keep the meter and video display perfectly still for the whole calibration. Even slightly moving the meter could affect how the ambient light is detected by the meter.

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post #11 of 15 Old 01-28-2014, 02:56 PM
 
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Quote:
Originally Posted by Doug Blackburn View Post

I still use window patterns where the window is about 10% of the area of the screen and surrounded by black. There's a lot of recent hysteria about avoiding all effects of automatic brightness limiting by using either very small window patterns (which are problematic for some meters to read accurately (depends on meter design) and constant Average Picture Level (APL) that maintain the same light output for all windowed patterns. IMO, the plasma TV will never operate without brightness limiting so the calibration should include SOME brightness limiting to help keep images accurate. You can always re-measure gamma with APL patterns to see if it is horrible or not.... if it is not horrible after using "tradiaional" 10%-size windows, you're good to go.

Some software supports subtracting ambient light from meter readings, but ambient light... daylight especially, changes constantly as the sun moves across the sky, as clouds come and go, as leaves on nearby trees appear, change size, change color, and fall again, as sun reflects from nearby buildings at different times of day, etc. If it is only artificial light you are worried about, there's more of a chance of a software's ambient light cancellation working but you'd have to test it to see how it works with your specific meter since meters all work differently and all respond to ambient light differently - mostly influenced by the angle of view of the meter, how close the meter is to the flat panel (obviously, for a projector calibration, ambient light has to be off completely), and how the meter "sits" against the panel.

You'd think by now there would some kind of data that would show an average % of time movies use scenes that trigger ABL or some kind of an indicator as to which windows one should use to optimize their calibration for specific content. Heck, I think that a movie should include it as a part of its specs, like duration, size, encoding, etc. There should be profiles so that plasma owners can create and save several calibrations and apply the one that fits the content the most For example a movie with many white scenes could be "Profile Delta" and would be best seen using 25% APL windows.

Dang, I calibrated the plasma I gave as a birthday present to my folks using small 2% windows, but I haven't seen any difference between them and using HCFR windows, which are much bigger.
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post #12 of 15 Old 01-28-2014, 08:12 PM
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Mine always looks too blue in the bright white areas(high contrast ratio scenes).Does not look anywhere close too yellow d65.Anyone have a suggestion too fix this other than get a meter?

2 pt only on tv-I can't lower blue gain anymore.raising red g actually makes brightest whites appear more blue.Raising green g makes midtones/some shows washed out.I already have too much blue in the dark bias areas already.is it just a matter of getting the relationship between bias and gains right?Do I need too lower contrast?or is it just a limitation of the tv?
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post #13 of 15 Old 01-31-2014, 06:04 PM
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Thinking raising voltage the only thing that would help but I don't want too take back off.
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post #14 of 15 Old 01-31-2014, 08:33 PM
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Quote:
Originally Posted by Vic12345 View Post

Mine always looks too blue in the bright white areas(high contrast ratio scenes).Does not look anywhere close too yellow d65.Anyone have a suggestion too fix this other than get a meter?

2 pt only on tv-I can't lower blue gain anymore.raising red g actually makes brightest whites appear more blue.Raising green g makes midtones/some shows washed out.I already have too much blue in the dark bias areas already.is it just a matter of getting the relationship between bias and gains right?Do I need too lower contrast?or is it just a limitation of the tv?

Probably need to lower contrast.

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post #15 of 15 Old 02-01-2014, 03:04 PM
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I'll try that.thanks sotti
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