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post #1 of 18 Old 12-27-2018, 09:47 AM - Thread Starter
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Can you evaluate my gamma for BT 1886?

Happy holidays everyone!

As my title suggest since im new to calibration i have attached my gamma correction for bt 1886 with obviously 2.4 exponent.

Can someone tell me if its tracked accurately or if it needs adjustment?

Also i tried my cms controls but they seem to be bugged as nothing shofts no matter how much i adjust the values. Maybe im doung it wrong?

Thank you in advance for any assistance
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post #2 of 18 Old 12-27-2018, 10:33 AM
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Looks great as-is for grayscale and gamma. Most displays have lousy CMS controls. Try to meet the luminance targets for the primary colors, and hue for the secondaries. Hue may require some back and forth to get the best balance for cyan, magenta, and yellow. Once you get there, leave it at that.

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post #3 of 18 Old 12-27-2018, 10:47 AM - Thread Starter
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Thanks a ton buddy im really glad that you can confirm my greyscale and gamma are on spot!🙂

Now forgive my ignorance when you mention colour and hue you mean those are adjusted with cms controls? Since none of them for either cyan magenta are moving. And i have tried both of 75% and 100%

Am i missing something?
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post #4 of 18 Old 12-27-2018, 11:43 AM
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Quote:
Originally Posted by Rolls-Royce View Post
Looks great as-is for grayscale and gamma.
I’m not familiar the CalMAN. How do you check BT.1886 from the posted graph? All I can see is a slight dip in gamma at 10%.
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post #5 of 18 Old 12-27-2018, 01:03 PM
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You can also use LightSpace DPS (free) to do your own verifiction.

That will use your specific min/max values to calculate the correct target BT1886 for your display.

But, I'd also recommend a pure power law - BT1886 has issue in washing out the shadows on any displays that has a lifted black.

This is explained here: http://www.lightillusion.com/error.html#bt1886_gamma

Steve
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post #6 of 18 Old 12-27-2018, 01:23 PM - Thread Starter
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Quote:
Originally Posted by Light Illusion View Post
You can also use LightSpace DPS (free) to do your own verifiction.

That will use your specific min/max values to calculate the correct target BT1886 for your display.

But, I'd also recommend a pure power law - BT1886 has issue in washing out the shadows on any displays that has a lifted black.

This is explained here: http://www.lightillusion.com/error.html#bt1886_gamma

Steve
Thanks for the feedback as well Steve🙂 from what i can tell when i was just playing on my ps4 shadows and black look on spot for my taste i did not notice any issues with it.

But you are a professional so you must know better. My tv has only bt1886 gamma for sdr, which means i can only change a slider +1 -1 etc. is it still possible to have a flat gamma curve of 2.2 or 2.4?

Also the slight dip on 10% of my gamma is that an issue?

Looking forward for further insight on the matter if possible and thanks everyone for assisting me
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post #7 of 18 Old 12-27-2018, 01:42 PM
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Quote:
Originally Posted by Dominic Chan View Post
I’m not familiar the CalMAN. How do you check BT.1886 from the posted graph? All I can see is a slight dip in gamma at 10%.
Essentially, I'm just going by how it's following the majority of that yellow target line, which is the only info he provided. I really can't evaluate BT.1886 tracking without the actual and target numbers. Depending on the meter used, how its set up in CalMAN, and how well the OP set his display's black level, those readings below 10% may be "iffy". It tracks the targets well above that point, which is why I said it looks good. At this point, I'd be watching content I'm familiar with to see if the shadow areas look natural or if more work is needed in the darker grays.

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post #8 of 18 Old 12-27-2018, 02:27 PM - Thread Starter
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Quote:
Originally Posted by Rolls-Royce View Post
Quote:
Originally Posted by Dominic Chan View Post
I’m not familiar the CalMAN. How do you check BT.1886 from the posted graph? All I can see is a slight dip in gamma at 10%.
Essentially, I'm just going by how it's following the majority of that yellow target line, which is the only info he provided. I really can't evaluate BT.1886 tracking without the actual and target numbers. Depending on the meter used, how its set up in CalMAN, and how well the OP set his display's black level, those readings below 10% may be "iffy". It tracks the targets well above that point, which is why I said it looks good. At this point, I'd be watching content I'm familiar with to see if the shadow areas look natural or if more work is needed in the darker grays.
So is Bt1886 supposed to have a dip at 10 or below?

Im watching familiar shows as we speak. Depth its there due to my gamma of 2.8 which gives blacks a good black feeling and not grey

Really i wish a professional was available in my area but theres is none sadly. As you understand to me it can look really good with my results but only a professional can really tell.

With my overal deltaE and gamma results, i dont think i should bother something else since im not confident it will yield a better average deltaE or gamma.

By the way if i change my brightness black level i mean does it change my graycale and will i need to recalibrate my 2 point?
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post #9 of 18 Old 12-27-2018, 02:56 PM
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Quote:
Originally Posted by Mikedagreat90 View Post
So is Bt1886 supposed to have a dip at 10 or below?
Unless you have absolute block (like OLED), BT1886 will have a gamma dip in the low end, meaning brighter shadow levels than gamma 2.4
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By the way if i change my brightness black level i mean does it change my graycale and will i need to recalibrate my 2 point?
Usually Brightness is adjusted before white balance and Gamma, but there may be some iteration involved.
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post #10 of 18 Old 12-27-2018, 03:04 PM
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Quote:
Originally Posted by Mikedagreat90 View Post
So is Bt1886 supposed to have a dip at 10 or below?

Im watching familiar shows as we speak. Depth its there due to my gamma of 2.8 which gives blacks a good black feeling and not grey

Really i wish a professional was available in my area but theres is none sadly. As you understand to me it can look really good with my results but only a professional can really tell.

With my overal deltaE and gamma results, i dont think i should bother something else since im not confident it will yield a better average deltaE or gamma.

By the way if i change my brightness black level i mean does it change my graycale and will i need to recalibrate my 2 point?
Strictly speaking, the thin white "measured" line and the yellow target line should be indistinguishable all the way across from 0% to 100%. Realistically, that isn't going to happen, especially as you get down close to 0%. No meter can read accurately at 0 nits, and most won't at some point above that, depending on the meter. Also, most displays' factory controls don't give you enough control for fine adjustment down low. If you're happy with your blacks and shadow areas, that's all that matters.
Technically, if you adjust your black level, you should redo your gray scale. It'll change the gamma targets, which should be based in part on the actual luminance at black. But if you're only bumping the Brightness control a click or so, you can probably realistically skip a redo. It's easy to get caught up chasing dEs and prettier graphs. Relax and enjoy some content!

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post #11 of 18 Old 12-28-2018, 08:24 AM
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Actually, for a 0% and 100% grey scale patch there is no valid Gamma value, as gamma is change between two points.
But, the dip in gamma, which equates to a brightening of the image, looks too excessive to be correct for BT1886, if the target gamma line is a pure power law.
If the target gamma line is BT1886, then it is plain wrong.

For some info on BT1886 see: http://www.lightillusion.com/error.html#bt1886_gamma

You can see there the expected gamma change relative to a 2.4 power law gamma for a display with a nominal 0.05 nits black level.

Steve
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post #12 of 18 Old 12-28-2018, 08:54 AM
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Quote:
Originally Posted by Light Illusion View Post
Actually, for a 0% and 100% grey scale patch there is no valid Gamma value, as gamma is change between two points.
But, the dip in gamma, which equates to a brightening of the image, looks too excessive to be correct for BT1886, if the target gamma line is a pure power law.
If the target gamma line is BT1886, then it is plain wrong.

For some info on BT1886 see: http://www.lightillusion.com/error.html#bt1886_gamma

You can see there the expected gamma change relative to a 2.4 power law gamma for a display with a nominal 0.05 nits black level.

Steve
Thanks, Steve!

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post #13 of 18 Old 12-28-2018, 08:59 AM
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Quote:
Originally Posted by Light Illusion View Post
Actually, for a 0% and 100% grey scale patch there is no valid Gamma value, as gamma is change between two points.
But, the dip in gamma, which equates to a brightening of the image, looks too excessive to be correct for BT1886, if the target gamma line is a pure power law.
If the target gamma line is BT1886, then it is plain wrong.
I don't know CalMAN, but AFAIK the line segment between 0 and 10% should be ignored. It's simply a linear interpolation between the values at 10% and at 0% (the latter of which is undefined, as Steve explained).

You will need more measurement points between 0% and 10% to able to evaluate the BT1886 calibration.
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post #14 of 18 Old 01-02-2019, 02:25 PM
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Originally Posted by Mikedagreat90 View Post
My tv has only bt1886 gamma for sdr, which means i can only change a slider +1 -1 etc. is it still possible to have a flat gamma curve of 2.2 or 2.4?
Hi, what display model you are trying to calibrate and how you generate your patches for measurements?

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post #15 of 18 Old 01-02-2019, 03:37 PM
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Hi, what display model you are trying to calibrate and how you generate your patches for measurements?
Sounds like a Samsung TV
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post #16 of 18 Old 01-03-2019, 03:43 AM - Thread Starter
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Hi Tedd. The most accurate ones i have is spears and munsil which i use through my ps4

Other rhan that through my firestick with mobileforge.

Yes its a 4k samsung nu7120.

So if for sdr i only have available bt1886 then should i leave the target at bt1886 in calman or should i manually choose 2.4?

Another thing im trying to figure out does each point need to be at 2.4? For example if i start measuring from 10% gradually then i see 2.35 2.36 until i reach 100% which indicates 2.40 or 2.41. Will this be my total gamma or is it only for 100%?

Sounds like a Samsung TV[/QUOTE]
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post #17 of 18 Old 01-04-2019, 02:31 PM
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post #18 of 18 Old 01-04-2019, 02:49 PM
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Quote:
Originally Posted by Mikedagreat90 View Post
Hi Tedd. The most accurate ones i have is spears and munsil which i use through my ps4

Other rhan that through my firestick with mobileforge.

Yes its a 4k samsung nu7120.

So if for sdr i only have available bt1886 then should i leave the target at bt1886 in calman or should i manually choose 2.4?

Another thing im trying to figure out does each point need to be at 2.4? For example if i start measuring from 10% gradually then i see 2.35 2.36 until i reach 100% which indicates 2.40 or 2.41. Will this be my total gamma or is it only for 100%?

Sounds like a Samsung TV
Hi, the BT1886 preset you see if an un-calibrated preset (just a name), nothing to do with what target you will use to calibrate your grayscale, you can use 2.4 as target gamma, no problem.

The calibration software, based to your black/white reading, it will calculate the target luminance for each of your grayscale steps, according to your selected target gamma value. Its normal your display to have deviations at random grayscale levels, so using the RGB balance controls you can fix these errors.

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