Is Bt1886 th right gamma curve for broadcast tv? - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 6 Old 02-12-2017, 06:04 PM - Thread Starter
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Is Bt1886 th right gamma curve for broadcast tv?

I would like to get the opinion about something.

Is BT1886 the best gamma curve for broadcast tv?
I dont watch blurays anymore now that I cant rent them anywhere near me and I dont stream shows either.
So my tv is basically used for watching shows and movies from broadcast TV.

My brightness is set that 16 is clipped and contrast clips at 235.

But all the scenes that do not have dark/blacker colors the picture is amazing but as soon black/dark enters the picture they overwhelm the picture and seem to darken the whole scene.
The problem is that I am seeing this in pretty much all of the shows even on the sitcoms that are supposed to be cheerful and lively like the big bang or Kevin can wait.

I can still see details in the black/dark areas so I dont think they are crushing which brings me to the gamma curve as I am trying to find what could be the problem.
Because of the BT1886 curve. is the 10%/20% too low for broadcast? Is it because of the color temperature? 10% is showing lower than 65k or maybe 20% and 30% are higher than 65K and they shouldn't?

What am I missing?

Last edited by HammerJoe; Yesterday at 08:51 PM.
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post #2 of 6 Old Yesterday, 01:16 PM
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Quote:
Originally Posted by HammerJoe View Post
I would like to get the opinion about something.

Is BT1886 the best gamma curve for broadcast tv?
I dont watch burays anymore now that I cant rent them anywhere near me and I dont stream shows either.
So my tv is basically for watching shows and movies from broadcast TV.

My brightness is set that 16 is clipped and contrast clips at 254.

But all the scenes that do not have dark/blacker colors the picture is amazing but as soon black/dark enters the picture they overwhelm the picture and seem to darken the whole scene.
The problem is that I am seeing this in pretty much all of the shows even on the sitcoms that are supposed to be cheerfull and lively like the big bang or Kevib cab wait

I can still see details in the black/dark areas so I dont think they are crushing which brings me to the gamma curve as I am trying to find what could be the problem.
Because of the BT1886 curve is the 10%/20% too low for broadcast? Is it because of the color temperature? 10% is showing lower than 65k or maybe 20% and 30% are higher than 65K and they shouldn't?

What am I missing?
Hi, what display do you have? The issue you are talking is related with your display characteristics, it's dimming globally the scenes with low APL so you loose dynamic range, it's dimming to provide better black level but you loose peak output the same time, so the picture look so dark to these scenes (low contrast ratio)

BTW when you are calibrating BT.1886, you have to trick your display to keep it's backlight open to measure it's real black level (and not a fake 0 nits with backlight off...which is not the correct black level of your display...unless you have an OLED), you have to prevent it from dimming completely when you will display a black (16) window pattern, if it's dimmed completely you will not able to measure your real black and the BT.1886 targets per grayscale step will not be calculated correctly,,,..you will get a fake infinite contrast ratio also.

For example, from the users of my calibration disk, before each pattern I have 2 sec text announcement of what pattern it will be displayed (see video below as example....I don't put text/numbers to actual patterns.....external pattern generators don't display text/numbers also, when you have text; this may affect some readings), so if you pause the pattern info screen (which is located to the middle right side of the screen (not affecting the meter reading since it's aiming to the center of the screen) this will provide you a real black level measurement, so a realistic calculation of your gamma for better near black performance and generally the whole grayscale calculation.


Ted's LightSpace CMS Calibration Disk Free Version for Free Calibration Software: LightSpace DPS / CalMAN ColorChecker / HCFR
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V/P: eeColor 3D LUT Box - P/G: DVDO AVLab TPG
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post #3 of 6 Old Yesterday, 08:50 PM - Thread Starter
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Originally Posted by ConnecTEDDD View Post
Hi, what display do you have? The issue you are talking is related with your display characteristics, it's dimming globally the scenes with low APL so you loose dynamic range, it's dimming to provide better black level but you loose peak output the same time, so the picture look so dark to these scenes (low contrast ratio)
What an interesting twist.
The TV is a Hisense 65cu6200 (model H7B series).
Its edge lit I believe with no local dimming.

Quote:
BTW when you are calibrating BT.1886, you have to trick your display to keep it's backlight open to measure it's real black level (and not a fake 0 nits with backlight off...which is not the correct black level of your display...unless you have an OLED), you have to prevent it from dimming completely when you will display a black (16) window pattern, if it's dimmed completely you will not able to measure your real black and the BT.1886 targets per grayscale step will not be calculated correctly,,,..you will get a fake infinite contrast ratio also.
I used both fields and window patterns. Would the APL do the trick and keep backlight open at all times ans thus get a proper greyscale line?
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post #4 of 6 Old Today, 04:10 AM
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What an interesting twist.
The TV is a Hisense 65cu6200 (model H7B series).
Its edge lit I believe with no local dimming.


I used both fields and window patterns. Would the APL do the trick and keep backlight open at all times ans thus get a proper greyscale line?

It's Edge-LED, so it's dimming globally.

The APL patterns can keep the backlight open.

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post #5 of 6 Old Today, 08:13 AM - Thread Starter
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Quote:
Originally Posted by ConnecTEDDD View Post
It's Edge-LED, so it's dimming globally.

The APL patterns can keep the backlight open.
Thanks for the information. I will give it a try and see if it makes a difference.

It makes sense because when theres no blacks involved the picture is really vibrant and lively.

If i understood what you said when i using the 0% pattern the TV might turn black light down to mae black blacker but when watching regular TV that will probably never happen because theres never a total black screen except when changing scenes?

Last edited by HammerJoe; Today at 05:38 PM.
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post #6 of 6 Old Today, 04:54 PM
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Originally Posted by HammerJoe View Post
If i understood wear you said when i used the 0% pattern the TV might turn blacklight down but when watching regular TV tray should never happen because a total black screen is rare?
With TV channels, you always have the channel logo displayed.. so it will never dim completely.

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