Gamma values used on your systems? - Page 7 - AVS Forum
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post #181 of 395 Old 08-11-2009, 07:57 AM
 
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Originally Posted by lcaillo View Post

If I, who has been studying color science and video for 30 years can't sort out what you are trying to communicate, how is the average reader supposed to?

Because it's over your head sir.

Heck get Poynton himself, and I will explain what this (implicit) Rec color space or Rec 709..or said target of 2.5. I actually calibrate said DI workflow btw!
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post #182 of 395 Old 08-11-2009, 08:10 AM
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I am sorry, but I cannot make out exactly what your point is and what issue you have with Charles Poynton on the matter. It seems like you are attributing to him ideas with which he may not concur. If you can more clearly articulate the issue, I will be happy to ask him to clarify the point. From what I have seen so far, he would not bother as there is not a clear point being conveyed and his name is just being tossed about as a means of conducting an argument. The man is rather well known for getting to the heart of the matter and being very precise in the language that he uses to discuss these issues. As for being over my head, I do not see the need for insults nor condescension. I am truly trying to comprehend your positions here. Do you want to be understood or do you want to continue to pretend that you are somehow smarter than the rest of us? If the latter I am done. If the former, then put up...elucidate your points...or be gone, please.

Yes, calibration is important...every user should be calibrated.

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post #183 of 395 Old 08-11-2009, 08:25 AM
 
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Can you note where I got a single IRE value out of place or in error? Chris says I can't encode digitally said IRE LEVEL?. He is WRONG about that sir!


The deviation from the default profile thats loaded inside my 12-14 bit cinema camera, the actual hardware and the matrix (Rec 709) represent R'G'B' normalized "voltage" or Y' .That concept of luminance btw is actually encoded per rec 709
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post #184 of 395 Old 08-11-2009, 09:29 AM
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Quote:
Originally Posted by tbrunet View Post

Can you note where I got a single IRE value out of place or in error? Chris says I can't encode digitally said IRE LEVEL?. He is WRONG about that sir!


The deviation from the default profile thats loaded inside my 12-14 bit cinema camera, the actual hardware and the matrix (Rec 709) represent R'G'B' normalized "voltage" or Y' .That concept of luminance btw is actually encoded per rec 709

TB,

You are all over the place in your typical response pattern. Without answering specific pointed questions you are looking rather foolish. I would say to you to just drop the debate and move on. As has been stated; "be gone".

MAK
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post #185 of 395 Old 08-11-2009, 09:37 AM
 
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Never mind racerxnet, I just got a pm from a forum member add he stated in black and white.

"My comments are actually backed up by real science fact."

So please, ask your question if you have one. because your position of me being ignorant are not valid in the particular case.

Maybe the concept of an IRE is beyond human comprehension, whatever "it" is I can define it for you perfectly 100% of the time.
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post #186 of 395 Old 08-11-2009, 09:38 AM
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Have missed this thread apparently, so I'm not up to speed what you've discussed earlier. Except who is right and who isn't ;-)

But how do one go about in adjusting the gamma ?
I'm using a HTPC, got a Spyder 2, have done greyscale calib. (room for improvement of course).
E.g. in ffdshow you can create curves, but where do you start in regard to the points to adjust the low end ?

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post #187 of 395 Old 08-11-2009, 10:08 AM
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I came across this paper again today when looking for something else entirely.

I've not been keeping up with this topic now, but it seems relevant:

http://www.poynton.com/notes/PU-PR-I...PR-IS.book.pdf
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post #188 of 395 Old 08-11-2009, 01:03 PM
 
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Mr. Poynton is addressing this very topic btw in that doc

My position:
Colorist convey the intention of RGB images. A colorist adjust relative image intent with reference to a known 2.2 D65 target. And as long as the rec 709 power function has connections to NTSC smpte TV standards, then the idea is

*a "artist" understands color science enough that when he yanks gamma it's for a reason and these tweaks are propagated as intentional additional pre distortion. This intent is intentional deviation from a default linear 1:1 correlation.

Watch any DVD or Bluray..could one say it looks filmlike?

Do different movies have a unique tone or appearance?

Are all recordings REC 709?
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post #189 of 395 Old 08-11-2009, 01:32 PM
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Quote:
Originally Posted by tbrunet View Post

Never mind racerxnet, I just got a pm from a forum member add he stated in black and white.

"My comments are actually backed up by real science fact."

Maybe your "friend" can answer Chris's question for you, since you don't seem able to. And what positions of yours does your "friend" claim are backed by real science fact:

- That the highest on/off CR possible with REC.709 is 219:1.
- That Charles Poynton's position is that the standard for video is that the displays do 2.2 gamma.

Something else?

I seem to recall you using this thing in the past that some mysterious person PMed you and so you must be right, as you were claiming some ridiculous stuff. Heck, you and DefininerOfReality were sticking together on the forum just a year ago to claim that gamma didn't apply to digital. You could have banded together with somebody ignorant like that in PMs and since you couldn't figure out that DefinerOfReality was wrong when he claimed that gamma didn't apply to digital and so 50% video level (or 50 IRE) would result in 5 ft-lamberts if 100% video level was 10 ft-lamberts, out in the open, what are the odds that you would figure something like that out in PMs?

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post #190 of 395 Old 08-11-2009, 01:37 PM
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Quote:
Originally Posted by darinp2 View Post

- That the highest on/off CR possible with REC.709 is 219:1.

Uhh, I hesitate to wade into this swamp battle, but how would any display spec which allows for absolute black be capable of affecting maximum possible CR? That's purely a function of the output device...!
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post #191 of 395 Old 08-11-2009, 01:46 PM
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Originally Posted by PeriSoft View Post

Uhh, I hesitate to wade into this swamp battle, but how would any display spec which allows for absolute black be capable of affecting maximum possible CR? That's purely a function of the output device...!

A spec can define what is possible. The output device could then do less than that, as we see. For instance, we have projectors that only do 1000:1 on/off CR and if you compare those to a CRT setup reasonably well, it is quite a difference (the absolute black being much more gray on the digital with low on/off CR like that if white is setup reasonably at all).

And if they want to limit the CR through the spec then they need to specifiy a lower CR than is possible.

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post #192 of 395 Old 08-11-2009, 01:48 PM
 
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Darin,

Poynton's public announcement and request for comment, is a plea to standardize a display OETF (Optical electrical transfer function).


I addressed the concept of gamma and intentionally propagating uniquie image info. Above I've outlined how "art" is created and how the digital image is essentially and perceptually conveyed in analog or digital form.

It seems a “digital” representation of gamma for some reason results in masive confusion on how one would deviate from Rec 709 i.e. how the colorist “enhances” look. Essentially modifying the gamma coding paradigm altogether and at the same time target ntsc color space
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post #193 of 395 Old 08-11-2009, 01:50 PM
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Quote:
Originally Posted by darinp2 View Post

A spec can define what is possible. The output device could then do less than that, as we see. For instance, we have projectors that only do 1000:1 on/off CR and if you compare those to a CRT setup reasonably well, it is quite a difference (the absolute black being much more gray on the digital with low on/off CR like that if white is setup reasonably at all).

OK, so it's more of a, "thou shalt provide at least this capability if you want to conform", not an intrinsic part of the definition (as it would be if it described a minimum luminance of N and a maximum luminance of 219N, in which case that would limit the CR via the internal standard rather than the output device's capability).
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post #194 of 395 Old 08-11-2009, 01:58 PM
 
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Darin is unable to even argue one specific point I've made in this thread. He finds a quote from me years old where I may have been in error. I have apologized publicly here on this forum and to Alan in pm. I admitted my error. But come to find out I was not 100% wrong as the big pic goes.

Problem IS Darin does not understand what gamma really really is especially with respect to a normalized tv signal voltage.


Sorry them be the facts.
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post #195 of 395 Old 08-11-2009, 02:02 PM
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Quote:
Originally Posted by tbrunet View Post

Darin,

Poynton's public announcement and request for comment, is a plea to standardize a display OETF (Optical electrical transfer function).

Poynton says:
Quote:


The electrostatic characteristics of a CRT's electron gun cause a CRT tohave nonlinear response from voltage to light - the EOCF. Since the
earliest days of television, the display power exponent for studio video has been about 2.4, and this value remains representative of today's studio displays - even those using non-CRT technology.
...
The de facto 2.4-power function of today's reference studio displays almost perfectly inverts L*
...
Perceptually correct reproduction is obtained by modifying image data, thereby altering the end-to-end relationship of scene luminance to reproduced luminance. In a greyscale system, a suitable correction can often be accomplished by arranging the system so that a gentle end-to-end power function acts upon relative scene luminance. Today, we are more interested in colour reproduction than in grayscale reproduction; a good starting point for the required colour image modification involves imposition, to each of the red, green, and blue tristimulus values, of a modest end-to-end power function. For a typical studio scene intended for display at about 100 cd·m2 in a dim surround, a common baseline correction can be accomplished by using an end-to-end power function having an exponent of about 1.2. The power function increases contrast and colour saturation in the reproduced midtones, relative to the midtones of the scene. The EOCF of today's studio displays closely approximates a 2.4-power function.
...
EOCF of a studio reference display should be standardized based upon a 2.35-power function.

Yet you claimed that he supported 2.2 as the display's gamma. Are you having trouble comprehending the difference between what you claim Poynton supported and what Poynton actually says he supports?

The subject of this thread is what the gamma of the displays are.

--Darin

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post #196 of 395 Old 08-11-2009, 02:04 PM
 
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Originally Posted by darinp2 View Post

Maybe your "friend" can answer

He is participating in this thread so maybe you will see a pm from him?

This persons calibrates displays and said my comments basically align with the science as it is understood today.

I know color science is complicated but it's not beyond comprehension..nor is 2.222222222 gamma
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post #197 of 395 Old 08-11-2009, 02:07 PM
 
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Quote:
Originally Posted by darinp2 View Post

Poynton says:Yet you claimed that he supported 2.2 as the display's gamma. Are you having trouble comprehending the difference between what you claim Poynton supported and what Poynton actually says he supports?

Darin I manage and calibrate many A/V system here.

Are you suggesting I can't measure video levels correctly?

Should Poynton come by and calibrate all my system for me? for the ideal .51 emphasis? and call it REC 709?
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post #198 of 395 Old 08-11-2009, 02:08 PM
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Quote:
Originally Posted by tbrunet View Post

Darin is unable to even argue one specific point I've made in this thread. He finds a quote from me years old where I may have been in error. I have apologized publicly here on this forum and to Alan in pm. I admitted my error. But come to find out I was not 100% wrong as the big pic goes.

Problem IS Darin does not understand what gamma really really is especially with respect to a normalized tv signal voltage.

What quote is that from year's ago that you apologized for? Just last year you said that gamma doesn't apply to digital. That sure wasn't years ago, although you did spend years playing tricks with the word "linear" to try to make it look like Dr. Soneira supported your position about the highest on/off CR possible.

After all these years, if your position about the highest possible on/off CR with REC.709 isn't 219:1, then what is it? You've been arguing against on/off CR for years, so you should be able to answer that.

And once again you play this trick claiming I don't understand gamma, yet you still can't answer Chris's question about what really happens and avoided my question for years about what light level a 10% video level would result in and when you finally attempted it, couldn't even get in the ballpark. So, if you understand gamma and I don't, then kindly tell people approximately how much light should come off a display for different encoding levels if (235, 128, 128) is 10 ft-lamberts:

(128, 128, 128): ?? ft-lamberts
(20, 128, 128): ?? ft-lamberts

You can add lots of words about how well you understand a subject matter, but when it comes down to actually answering real light levels that a person can check to see if you have a clue what you are talking about, you add post after post with no answer in order to get as far as from the specific questions as you can.

As you have done in this thread. What are you up to now, about 35 posts since I asked if you agreed with Poynton on one specific thing and still no answer. Not even that you don't know if you agree with him or not.

--Darin

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post #199 of 395 Old 08-11-2009, 02:11 PM
 
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Darin I just asked you if Poynton could better cal my digital production HD workflow including hardware for .51 unity?
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post #200 of 395 Old 08-11-2009, 02:13 PM
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Quote:
Originally Posted by tbrunet View Post

Darin I manage and calibrate many A/V system here.

Are you suggesting I can't measure video levels correctly?

In about 4 years you've showed that you can't. You told me you would measure light levels off a display and you have yet to do it. You either aren't smart enough to comprehend the difference between measuring a voltage inside and measuring the light level off the display, or you won't do it because it will go against other claims of your's.

If you know how to measure video levels correctly then why did you say a year ago that gamma doesn't apply to digital to support DefinerOfReality claiming that 50% video level would result in 5 ft-lamberts if 100% video level is 10 ft-lamberts?

You are welcome to measure in order to answer Chris's question if you don't know enough to be able to calculate it.

Instead of asking whether I think you don't know how to do something why don't you answer the question to show that you do know how? You played the same kinds of tricks for over a year in avoiding my question and how bright 10% video level would be and then when you finally did answer you showed that you didn't actually know how to do it.

And just as I predicted, instead of answering a straightforward question you try to get away from the question by asking more questions of your own, all the while knowing that you will never answer the original question no matter how many of your questions other people answer. You will just try to go in circles as long as you can in order to avoid the straightforward question. Nothing new for you.

I think people can see that racerxnet was right. You are trying to dance away from questions.

--Darin

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post #201 of 395 Old 08-11-2009, 02:17 PM
 
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Quote:
Originally Posted by darinp2 View Post

Not even that you don't know if you agree with him or not.

I agree with Poynton and would add that 2.2 was an excellent choice btw since sRGB has adopted the paradigm.


I could care less how a given display manufacturer handles their OETF. The design of displays is a very interesting subject but has nothing to do with the actual image information being recorded. Rec 709
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post #202 of 395 Old 08-11-2009, 02:19 PM
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Originally Posted by tbrunet View Post

He finds a quote from me years old where I may have been in error. I have apologized publicly here on this forum and to Alan in pm. I admitted my error. But come to find out I was not 100% wrong as the big pic goes.

As far as this, there was one time that you apologized and then within a few days you took it back. That was about your claim that the highest on/off CR possible with REC.709 was 219:1. Since you took it back, why is it that you want a pass on that claim when you won't even say whether it is your current position or not, or what you current position is on the thing that you claimed so many other people were wrong about?

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post #203 of 395 Old 08-11-2009, 02:21 PM
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Quote:
Originally Posted by tbrunet View Post

I agree with Poynton ...

You agree with him about what? Poynton makes it pretty clear that the 2.2 of sRGB is not for video in a dim surround and studio monitors, from things I have already quoted from him.

He clearly says:
Quote:


The de facto 2.4-power function of today’s reference studio displays almost perfectly inverts L*
...
EOCF of a studio reference display should be standardized based upon a 2.35-power function.

So, what is it you agree with Poynton about? Please be clear.

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post #204 of 395 Old 08-11-2009, 02:22 PM
 
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Originally Posted by darinp2 View Post

In about 4 years you've showed that you can't.

The display is everything..if the colorist is tweaking gamma he better have a 2.2 @ D65 reference.

When he/she moves back (pedestal), white, gamma, iris, ect.

One needs to see down to ~1/2 IRE pedestal resolution. If the display is crushing blacks unrealistically then these tweaks are invalid and will probably look like crap!
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post #205 of 395 Old 08-11-2009, 02:26 PM
 
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"EOCF of a studio reference display should be standardized based upon a 2.35-power function."

Well in the real world color correction or color enhancement, the reference monitor should be 2.2 @ D65. If Poynton is saying the above..then he is mistaken on what happens inside the mastering environment

Ask Mr. D

PLEASE!
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post #206 of 395 Old 08-11-2009, 02:45 PM
 
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Originally Posted by darinp2 View Post

As far as this, there was one time that you apologized and then within a few days you took it back. That was about your claim that the highest on/off CR possible with REC.709 was 219:1.

Darin I was even probably right about that to fyi

Quote:


http://www.marcelpatek.com/gamma.html

For 8-bit grayscale gradient, there would be theoretically 8.2 f-stops (exposure zones, log2300 = 8.2). For all 256 levels, there would be about 256/8.2 = ~ 31 distinguishable levels per a zone.

Number of levels assumes complete adaptation to relatively narrow range of luminances around the evaluated neighboring levels.

This 8 ½ f-stop exposure Darin just happens to align with ~200:1 contrast for some unknown reason?
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post #207 of 395 Old 08-11-2009, 02:48 PM
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Quote:
Originally Posted by tbrunet View Post

Ask Mr. D

Mr. D already weighed in on the forum that he thought the de facto standard was becoming 2.2.

I think Poynton's paper was largely that he didn't want some de facto standard for 2.2 for the display because he doesn't think that is what mastering displays over the years have been doing. Poynton wants an actual standard for display gamma, not for people to assume one from a REC.709 curve, which wasn't for the display. REC.709 has a linear tail. I'm guessing that if Mr. D addressed that he would say that they aren't doing the linear tail on the display side.

So, how did they decide on 2.2? As Mr. D said, he just cares how the display is setup and that makes sense. But Poynton's position is that they have been setup a certain way that wasn't 2.2. Maybe that has changed. Mr. D could address whether they've been 2.2 for decades, or whether he thinks it is a more recent thing.

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post #208 of 395 Old 08-11-2009, 02:57 PM
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Quote:
Originally Posted by tbrunet View Post

Quote:
Originally Posted by darinp2 View Post

As far as this, there was one time that you apologized and then within a few days you took it back. That was about your claim that the highest on/off CR possible with REC.709 was 219:1. Since you took it back, why is it that you want a pass on that claim when you won't even say whether it is your current position or not, or what you current position is on the thing that you claimed so many other people were wrong about?

Darin I was even probably right about that to fyi

This 8 ½ f-stop exposure Darin just happens to align with ~200:1 contrast for some unknown reason?

I wanted to quote this so you couldn't delete it and have it go away.

To be clear, you want credit for a claim of yours being years ago and accuse me of only going over something you apologized for with your, "He finds a quote from me years old where I may have been in error." Yet, over the past 4 years you haven't figured out enough to know whether you were right or not and you avoid simple questions either because you don't know the answer, or the answers would go against your claim there.

So, which is it, are you a person how is sticking with your claim that on/off CR can't be above 200:1 or not? You told people that they need to trust you because you are the engineer and have 30 years in this field, yet you are sticking with this 200:1 claim right? All while refusing to answer Chris's question that is related to this matter.

If you want to stick with that claim then answer this question:
Quote:
Originally Posted by darinp2 View Post

So, if you understand gamma and I don't, then kindly tell people approximately how much light should come off a display for different encoding levels if (235, 128, 128) is 10 ft-lamberts:

(128, 128, 128): ?? ft-lamberts
(20, 128, 128): ?? ft-lamberts

Maybe you can get Mr. D to agree with you that the highest on/off CR possible with 8 bit data REC.709 data is ~200:1. I doubt he would do that, but you can ask.

For others here, if tbrunet would answer the questions about how much light results from different specific levels people could check them. But instead he will avoid those and probably keep doing things like a year ago claiming that gamma didn't apply to digital. Maybe it is all to support his claim from almost 4 years ago that the highest on/off CR could go was 219:1.

Anybody else here ever looked at a display with about 200:1 on/off CR in a dark room before to see what that looks like?

--Darin

This is the AV Science Forum. Please don't be gullible and please do remember the saying, "Fool me once, shame on you. Fool me twice, shame on me."
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post #209 of 395 Old 08-11-2009, 03:02 PM
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Quote:
Originally Posted by tbrunet View Post

Quote:
Originally Posted by darinp2 View Post

As far as this, there was one time that you apologized and then within a few days you took it back. That was about your claim that the highest on/off CR possible with REC.709 was 219:1. Since you took it back, why is it that you want a pass on that claim when you won't even say whether it is your current position or not, or what you current position is on the thing that you claimed so many other people were wrong about?

Darin I was even probably right about that to fyi

Here is a post where Jason Turk measured on/off CR for a Sony HW10:

http://www.avsforum.com/avs-vb/showt...3#post14572473
Quote:
Originally Posted by Jason Turk View Post

Contrast/Black Levels: As mentioned, the unit is rated at 30000:1 on/off contrast, more than the previous VW40 (with iris). Originally I measured the unit at 16995:1, but then realizing I made an error. After remeasuring it, I got 24353:1 on/off! Kudos to Sony for impressive contrast on a lower cost SXRD.

Is it your claim that Jason measured it wrong?

Have you ever in your life measured on/off CR for anything?

--Darin

This is the AV Science Forum. Please don't be gullible and please do remember the saying, "Fool me once, shame on you. Fool me twice, shame on me."
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post #210 of 395 Old 08-11-2009, 03:05 PM
 
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http://www.marcelpatek.com/gamma.html

Note*: if we send linearly sampled data through a power function and quantize them, we will lose certain number of levels, depending on the number of bits of input and the number of bits of output. For example if we would send 256 linearly spaced levels (8-bit encoding) through the gamma compression curve of 0.4545 ( = 1/2.2), we would lose 72 levels to give us only 184 to work with. However, if our camera uses 10 or 12 bits to represent the captured linear RAW data, the gamma compression with the same power coefficient of 0.4545 would preserve all 256 levels in 8-bit encoding. See the Bruce Lindbloom's Level Calculator for details.
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