Gamma S Curve Setting - AVS Forum
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post #1 of 61 Old 07-17-2010, 05:51 PM - Thread Starter
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I just purchases a new Panasonic Professional Plasma Display that has lots of setting.

There is a Gamma S curve setting. My question is what does this setting do?

Currently I have Gamma set to 2.2 but some folks believe the s setting tracks blacks, whites, and mid tones to more picture like quality.

What is the forums recommendation for gamma, and what is the s gamma setting used for?

Thanks
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post #2 of 61 Old 07-17-2010, 07:45 PM
 
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Quote:
Originally Posted by robert5545 View Post

I just purchases a new Panasonic Professional Plasma Display that has lots of setting.

There is a Gamma S curve setting. My question is what does this setting do?

Currently I have Gamma set to 2.2 but some folks believe the s setting tracks blacks, whites, and mid tones to more picture like quality.

What is the forums recommendation for gamma, and what is the s gamma setting used for?

Thanks

*begin rant about gamma*

S-curve is a bad setting, it artificially changes the brightness curve to make dark areas appear brighter and mid-brightess areas overly bright, causing white crush (loss of detail in bright areas) and a loss of dynamic range of contrast. A typical side effect of it is that skin tones can appear waxy due to the way it's artificially shifting around and packing together all the different shades of colours. That's the reason it's called S-curve because if you plot input brightness vs what brightness is actually coming off the screen the graph will be in the shape of a sideways S (it should be a flat line).

The correct gamma setting in order to produce all the shades of colours at the correct brightness is 2.2 (or 2.22 to be precise) but I have found on the consumer models such as my 50S10A I need to select 2.5 in order to for the TV to produce an actual gamma curve of 2.22.

But, you have a professional model which I'm assuming is made to a much higher standard, so they have probably implemented the gamma control accurately, meaning you should select 2.2. If the picture still looks a bit light and washed out you might want to try 2.4 or 2.5.

Either way, the reference target for gamma is 2.22 and in order to acheive proper brightness levels you should select whatever gamma setting produces closest to 2.22.
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post #3 of 61 Old 07-18-2010, 09:10 AM
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The reference target for gamma is not 2.22.
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post #4 of 61 Old 07-18-2010, 06:11 PM
 
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Originally Posted by D-Nice View Post

The reference target for gamma is not 2.22.

Strange...why does HCFR say 2.22 is the reference target for gamma? What should gamma be in order to mean the display is producing the same brightness that the input signal is telling it to?
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post #5 of 61 Old 07-18-2010, 07:19 PM
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Originally Posted by sonic_blue View Post

Strange...why does HCFR say 2.22 is the reference target for gamma? What should gamma be in order to mean the display is producing the same brightness that the input signal is telling it to?

You need to ask the creators of HCFR why they think 2.22 is reference. 2.22 is nice, but it may not be ideal if your display has an excellent dynamic range, excellent contrast ratio and is located in a light controlled room.
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post #6 of 61 Old 07-18-2010, 08:29 PM
 
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Originally Posted by D-Nice View Post

2.22 is nice, but it may not be ideal if your display has an excellent dynamic range, excellent contrast ratio and is located in a light controlled room.

You're talking about changing the picture to make it "ideal". Shouldn't the TV just display what it's being told to display? If I tell my Panasonic to display a colour at 30% brightness it should display it at 30%, not 20% or 40%. Wouldn't you agree?
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post #7 of 61 Old 07-18-2010, 09:07 PM
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I think you need to visit the display calibration forum and read up on gamma.
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post #8 of 61 Old 07-18-2010, 09:25 PM
 
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I am higher than thou and don't need to explain anything

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post #9 of 61 Old 07-19-2010, 06:19 AM
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I didn't find that funny. I never posted anything like that and I ask you remove the false post. Otherwise, I will report you to a moderator.
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post #10 of 61 Old 07-19-2010, 04:36 PM
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Ive always liked the look of a gamma of around 2.3 - 2.4 so its down to pref i think best is between 2.22 and 2.5.

I got the gamma on my G10 set to 2.5 not sure what it actually is though.
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post #11 of 61 Old 07-19-2010, 05:11 PM
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Quote:
Originally Posted by sonic_blue View Post

Strange...why does HCFR say 2.22 is the reference target for gamma? What should gamma be in order to mean the display is producing the same brightness that the input signal is telling it to?

Read this:

http://www.spectracal.com/Documents/...0_2.2or2.4.pdf
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post #12 of 61 Old 07-19-2010, 05:15 PM
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Originally Posted by rfbrown94 View Post

Read this:

http://www.spectracal.com/Documents/...0_2.2or2.4.pdf

You beat me to it
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post #13 of 61 Old 07-19-2010, 05:33 PM
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Originally Posted by D-Nice View Post

You beat me to it

I'm just an enthusiast calibrator, so I value your opinion on this. My interpretation of Poynton's article (especially after reading some of his other work) is that 1) it's dependent on viewing conditions and 2) standardization is needed. Do you agree?

Another question I'd like to ask since we're on the topic of S-shaped gamma curves. Have you ever been able to flatten the response on a Samsung PN58B650? I'd probably hire you just to flatten this thing if it's possible. Drives me crazy that I can't do it.
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post #14 of 61 Old 07-19-2010, 06:42 PM
 
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Originally Posted by rfbrown94 View Post

Read this:

http://www.spectracal.com/Documents/...0_2.2or2.4.pdf

Interesting, it seems to suggest that there is no universally agreed upon display gamma response, is that correct? I find this hard to accept; shouldn't it be a simple matter of plugging some Y numbers into a formula to determine how bright things should look? If I've set my 100% window to 40ftL, shouldn't my 50% window be 8.5ftL in order to appear half as bright as the 100% window?
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post #15 of 61 Old 07-19-2010, 06:50 PM
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Originally Posted by rfbrown94 View Post

I'm just an enthusiast calibrator, so I value your opinion on this. My interpretation of Poynton's article (especially after reading some of his other work) is that 1) it's dependent on viewing conditions and 2) standardization is needed. Do you agree?

Yes on both. That was the main reason why I posted that 2.22 is not Reference.
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post #16 of 61 Old 07-19-2010, 07:01 PM
 
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Originally Posted by D-Nice View Post

Yes on both. That was the main reason why I posted that 2.22 is not Reference.

Then what is reference? How bright should my 50% window be? Are there formulas for human light perception that can determine how bright it should be?
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post #17 of 61 Old 07-19-2010, 07:05 PM
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Originally Posted by sonic_blue View Post

Then what is reference? How bright should my 50% window be? Are there formulas for human light perception that can determine how bright it should be?

There is no reference. That's the point. Your target gamma depends on your viewing conditions. Stick with 2.22 if it looks good to you.
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post #18 of 61 Old 07-19-2010, 07:24 PM
 
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Originally Posted by rfbrown94 View Post

There is no reference. That's the point. Your target gamma depends on your viewing conditions. Stick with 2.22 if it looks good to you.

If we don't know what the reference is, then how is D-Nice saying what the reference isn't? According to the dummies guide to calibration, studio monitors are calibrated to 2.2. I'm pretty sure graphic artists use monitors that are calibrated to 2.2 as well. But then I read in the article you linked to that "classic BVM's have a gamma of around 2.4". What is a "classic" BVM? Are they currently being used to master video?

I just can't see how some studio monitors would be 2.4 while others are 2.2. If that were the case the brightness would be all over the place depending on which monitor was used.

It seems pretty simple to me - a 50% window should appear half as bright as 100% window, correct? Disregard ambient lighting because we always calibrate in a dark room. I would like to know how much light should be coming off the screen. Does anyone know?
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post #19 of 61 Old 07-19-2010, 07:43 PM
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If there isn't a defined reference gamma, please explain how my post stating 2.22 is not reference incorrect? I'll make it easy for you.... my post is correct.

You are more than welcome to continue thinking there is a reference and/or 2.22 is reference. You have been provided information from the person who basically wrote the book on this stuff that 2.22 is not reference and there isn't a gamma standard yet.

BTW, BMV is a studio reference CRT monitor that was made by Sony. It was, and in some cases still is, the standard for video mastering.

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Originally Posted by sonic_blue View Post

If we don't know what the reference is, then how is D-Nice saying what the reference isn't? According to the dummies guide to calibration, studio monitors are calibrated to 2.2. I'm pretty sure graphic artists use monitors that are calibrated to 2.2 as well. But then I read in the article you linked to that "classic BVM's have a gamma of around 2.4". What is a "classic" BVM? Are they currently being used to master video?

I just can't see how some studio monitors would be 2.4 while others are 2.2. If that were the case the brightness would be all over the place depending on which monitor was used.

It seems pretty simple to me - a 50% window should appear half as bright as 100% window, correct? Disregard ambient lighting because we always calibrate in a dark room. I would like to know how much light should be coming off the screen. Does anyone know?

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post #20 of 61 Old 07-19-2010, 08:17 PM
 
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Originally Posted by D-Nice View Post

If there isn't a defined reference gamma, please explain how my post stating 2.22 is not reference incorrect?

All I'm saying is...how do you know 2.22 is false if you don't know what true is?

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Originally Posted by D-Nice View Post

You are more than welcome to continue thinking there is a reference

If there isn't some sort of reference then what are all the reference monitors using? Is the dummies guide right or wrong about studio monitors using 2.2? If you know the answer to this then why not just come out and say it? Instead you beat around the bush taking the high stance, not saying anything other than I'm wrong and need to read up on the subject.


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Originally Posted by D-Nice View Post

BTW, BMV is a studio reference CRT monitor that was made by Sony. It was, and in some cases still is, the standard for video mastering.

Yes I know what a BVM is, my question was about the article refering to them as 'classic' and whether that indicates they are still being used today. You've said in 'some cases' they are. Can you clarify how much of current video content is being mastered for 2.4 gamma? I get the feeling it's being mastered for 2.2 but there seems to be some doubt about this.

Again, the very simple question regarding how bright a 50% window should be in relation to a 100% 40ftL window: do you know the answer to this question? It has nothing to do with reference gamma of studio monitors or lighting conditions and should be a simple case of math. I don't know the answer and I would suggest that if you don't know then neither of us are qualified to say what gamma should be.
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post #21 of 61 Old 07-19-2010, 08:26 PM
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Originally Posted by sonic_blue View Post

All I'm saying is...how do you know 2.22 is false if you don't know what true is?

RTF blog!!!!

Quote:


If there isn't some sort of reference then what are all the reference monitors using? Is the dummies guide right or wrong about studio monitors using 2.2? If you know the answer to this then why not just come out and say it? Instead you beat around the bush taking the high stance, not saying anything other than I'm wrong and need to read up on the subject.

I already told you the answer. 2.2 is not reference and there currently is not a defined reference for digital displays. How many times does that need to be repeated before you get it? I also advised you where to look to find more information regarding gamma (the display calibration forum). You chose to post that silly ass remark when I gave you that recommendation.

Quote:


Yes I know what a BVM is, my question was about the article refering to them as 'classic' and whether that indicates they are still being used today. You've said in 'some cases' they are. Can you clarify how much of current video content is being mastered for 2.4 gamma? I get the feeling it's being mastered for 2.2 but there seems to be some doubt about this.

At this point you are not going to be satisfied until someone tells you 2.2 is reference. Since that is the case, what I have posted and what Poynton has in his blog is meaningless.

Quote:


Again, the very simple question regarding how bright a 50% window should be in relation to a 100% 40ftL window: do you know the answer to this question?

READ what I posted above and figure it out.... or believe whatever you want.

Quote:


I don't know the answer and I would suggest that if you don't know then neither of us are qualified to say what gamma should be.

You don't know what the answer is, yet I've stated it time and time again? And you "suggest" I do something???? LMFAO


THERE IS NOT A DEFINED REFERENCE GAMMA! You choose the gamma based on the room lighting conditions. Geez!
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post #22 of 61 Old 07-19-2010, 08:30 PM
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Let it go, Sonic.

This has been hashed over for years. Here is a link to a very recent publication by Poynton. If the math is not of interest, just read the first paragraph of the introductory letter.

http://www.poynton.com/notes/PU-PR-I...n-PU-PR-IS.pdf

Larry
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post #23 of 61 Old 07-19-2010, 08:30 PM
 
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Oops it seems I have upset someone I guess the dummies guide was right about this being a "huge raging debate amongst calibrators".
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post #24 of 61 Old 07-19-2010, 08:35 PM
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Oops it seems I have upset someone I guess the dummies guide was right about this being a "huge raging debate amongst calibrators".

You probably need to stick with the "Dummies" guide as it seems to be the only thing you want to understand.
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post #25 of 61 Old 07-19-2010, 08:36 PM
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Originally Posted by LarryInRI View Post

Let it go, Sonic.

This has been hashed over for years. Here is a link to a very recent publication by Poynton. If the math is not of interest, just read the first paragraph of the introductory letter.

http://www.poynton.com/notes/PU-PR-I...n-PU-PR-IS.pdf

Larry

He will probably skip right over that publication and continue with his "why is 2.22 not reference" rant.
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post #26 of 61 Old 07-19-2010, 08:50 PM
 
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Originally Posted by D-Nice View Post

You probably need to stick with the "Dummies" guide as it seems to be the only thing you want to understand.

All I want to understand is how bright the 50% window should be in relation to the 100% window. This is a question that has absolutely nothing to do with response curves of cameras or studio monitors, so it should be fairly straight forward.
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post #27 of 61 Old 07-19-2010, 09:01 PM
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post #28 of 61 Old 07-19-2010, 09:06 PM
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Quote:
Originally Posted by sonic_blue View Post

All I want to understand is how bright the 50% window should be in relation to the 100% window. This is a question that has absolutely nothing to do with response curves of cameras or studio monitors, so it should be fairly straight forward.


Sonic,

The answer is simple: There is no simple answer. The 50% level is a function of the gamma you select.

It's all explained in the referenced document that I linked.

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post #29 of 61 Old 07-19-2010, 09:10 PM
 
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Originally Posted by LarryInRI View Post

Sonic,

The answer is simple: There is no simple answer. The 50% level is a function of the gamma you select.

Yes but shouldn't it appear half as bright as the 100% window? There's got to be a formula which says what appears "half as bright" to our eyes.

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It's all explained in the referenced document that I linked.

Thanks, reading it now.
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post #30 of 61 Old 07-19-2010, 10:00 PM
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Quote:
Originally Posted by sonic_blue View Post

All I want to understand is how bright the 50% window should be in relation to the 100% window. This is a question that has absolutely nothing to do with response curves of cameras or studio monitors, so it should be fairly straight forward.

sonic_blue,

The problem is to give u the answer, u would need to know what target gamma you are trying to go for. For a 100% window of 36ft/L, at a gamma of 2.22 (this is based on the maths that is defined for the gamma formula), the 50% window should be in the range of 7-8ft/L. These are ballpark figures. For a 40ft/L window and a gamma of about 2.2ish the 50% window shd read about 8.5ft/L.
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