Gamma, what is "higher" and what is "lower"? - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 21 Old 01-29-2017, 06:11 AM - Thread Starter
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Gamma, what is "higher" and what is "lower"?

I have read many articles and posts over the time talking about gamma and can't see a consensus on what is considered "high" gamma and what is considered "low" gamma. Experts' opinions seem to differ, or they get mixed up, when talking about gamma. I have calibrated several displays over the last year and still find myself being caught out. I am of the opinion that 2.4 is "lower" than 2.2, but I am willing to be corrected.

So, to keep it simple, is a gamma value of 2.2 higher or lower than a gamma value of 2.4?
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post #2 of 21 Old 01-29-2017, 07:52 AM
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Higher...... I think. I've wondered this too.
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post #3 of 21 Old 01-29-2017, 05:31 PM
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Quote:
Originally Posted by holdemphil View Post
I have read many articles and posts over the time talking about gamma and can't see a consensus on what is considered "high" gamma and what is considered "low" gamma. Experts' opinions seem to differ, or they get mixed up, when talking about gamma. I have calibrated several displays over the last year and still find myself being caught out. I am of the opinion that 2.4 is "lower" than 2.2, but I am willing to be corrected.

So, to keep it simple, is a gamma value of 2.2 higher or lower than a gamma value of 2.4?
To me, higher gamma simply means a numerically higher gamma value, i.e., 2.4 is a higher gamma value than 2.2. For a specific input, the output luminance is lower with a higher gamma value, but that's just the nature of gamma.

See, for example,
http://www.chromapure.com/colorscience-gamma.asp

I'd be interested in seeing which experts define it the opposite way.

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post #4 of 21 Old 01-30-2017, 06:09 AM
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The picture is an example of Gamma differences. The higher the gamma number the darker the blacks will be. Usually a higher gamma will add more depth to the picture and make it appear to have more contrast but if it is too high it will be too dark to see all the details in the picture or shadow detail. The photo shows this well as the higher gamma you no longer are able to see the wrinkles in his pants and not all the detail can be seen. The lower gamma looks washed out and lacks contrast and depth. Now with regards to calibration we have to remember this is going to vary on the source, display and viewing environment. For sake of argument let's say the source is perfect to calibrate the display.

One thing many calibrators do is make a custom gamma to make the picture look as good as possible and we also have to realize that consumer displays are not a 40" $40,000 reference monitor and we are not always viewing in the dark conditions with proper backlighting that these monitors are being used. So sometimes compromises have to be made to get the most out of the display. A calibrator can calibrate to 2.2, 2.4, BT1886 or whatever but sometimes it doesn't look as good as could but technically it would be accurate.

Some displays you can only pick various options for gamma and you pick the one that works best for that environment. Other displays you can alter the curve of the gamma. For instance let's say your overall gamma is 2.4 and gives a nice contrast and depth to the picture but you lose some shadow detail. You could make the low end of the curve 2.0 or 2.2 to bring out some shadow detail and still keep that depth and overall contrast to the picture. This is a generalization and will vary depending on display and viewing environment. So calibrations is often part science and part art. A good calibrator will know where to make compromises for that display and viewing environment.

I mention viewing environment as this is also very important. The TVs that are ISF certified mean that they have controls for adjusting the picture and have a night and a day mode so you can have two different calibrations for darker and brighter environments. They are not calibrated out of the box. THX certification means it has some presets that are close to reference. But the THX mode might not be the best choice depending on viewing environment. In a brighter environment an overall brighter picture is needed but a higher gamma at least at the darker end of the picture might be preferred to see the shadow detail.

Calibrators and enthusiast often argue about different gammas but in reality there are a lot of variables with sources, displays and environments that need to be factored for gamma and display calibrations. If you are calibrating a display don't just go by the numbers and test patterns, view a lot of different material as well. This way you will know how the numbers relate to real world viewing for that display. Then get the best picture you can for your display.
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post #5 of 21 Old 01-30-2017, 07:32 AM - Thread Starter
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Originally Posted by Ellebob View Post
The picture is an example of Gamma differences. The higher the gamma number the darker the blacks will be. Usually a higher gamma will add more depth to the picture and make it appear to have more contrast but if it is too high it will be too dark to see all the details in the picture or shadow detail. The photo shows this well as the higher gamma you no longer are able to see the wrinkles in his pants and not all the detail can be seen. The lower gamma looks washed out and lacks contrast and depth. Now with regards to calibration we have to remember this is going to vary on the source, display and viewing environment. For sake of argument let's say the source is perfect to calibrate the display.

One thing many calibrators do is make a custom gamma to make the picture look as good as possible and we also have to realize that consumer displays are not a 40" $40,000 reference monitor and we are not always viewing in the dark conditions with proper backlighting that these monitors are being used. So sometimes compromises have to be made to get the most out of the display. A calibrator can calibrate to 2.2, 2.4, BT1886 or whatever but sometimes it doesn't look as good as could but technically it would be accurate.

Some displays you can only pick various options for gamma and you pick the one that works best for that environment. Other displays you can alter the curve of the gamma. For instance let's say your overall gamma is 2.4 and gives a nice contrast and depth to the picture but you lose some shadow detail. You could make the low end of the curve 2.0 or 2.2 to bring out some shadow detail and still keep that depth and overall contrast to the picture. This is a generalization and will vary depending on display and viewing environment. So calibrations is often part science and part art. A good calibrator will know where to make compromises for that display and viewing environment.

I mention viewing environment as this is also very important. The TVs that are ISF certified mean that they have controls for adjusting the picture and have a night and a day mode so you can have two different calibrations for darker and brighter environments. They are not calibrated out of the box. THX certification means it has some presets that are close to reference. But the THX mode might not be the best choice depending on viewing environment. In a brighter environment an overall brighter picture is needed but a higher gamma at least at the darker end of the picture might be preferred to see the shadow detail.

Calibrators and enthusiast often argue about different gammas but in reality there are a lot of variables with sources, displays and environments that need to be factored for gamma and display calibrations. If you are calibrating a display don't just go by the numbers and test patterns, view a lot of different material as well. This way you will know how the numbers relate to real world viewing for that display. Then get the best picture you can for your display.
I appreciate your post, very informative. By the way you describe gamma you are on the side of the numerical argument, where a higher number is a "higher" gamma, even though it (2.4) has lower luminosity than 2.2. This is what I am looking for opinions on, as I understand gamma but both of these descriptions are used and confusion can easily be made. So far, including myself, the opinions ITT are 2-2 (unless my math is completely screwed!).
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post #6 of 21 Old 01-31-2017, 09:14 AM
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Without getting into a crapload of detail Display Gamma is (usually) a curve that describes the inverse of the Source Content Gamma curve bringing it back to the original level.

You can set your curve to the exact inverse of the sources curve or you can make it Higher or Lower to make the image Darker or Lighter.

Higher is darker, lower is brighter. You also have the option to make only the low end brighter or the high end darker, or anywhere in-between (i.e. non-power law gamma). Google "electro-optical transfer function".

The middle line is the original video luma ramp, and the two curves on the outside are display gamma and camera (source) gamma:
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post #7 of 21 Unread 04-05-2017, 11:23 AM
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Just thought I'd add my opinion as well. Gamma refers to how fast or slow a display comes out of black. Basically how many steps to get out of black between 0 and 100% on a 21pt grayscale. The higher the gamma the more steps out of black. That's why we percieve a dimmer picture but the peak luminance doesn't change (ideally).

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post #8 of 21 Unread 04-08-2017, 06:43 PM
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Here is something that might help

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post #9 of 21 Unread 04-08-2017, 06:47 PM
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Quote:
Originally Posted by holdemphil View Post
I have read many articles and posts over the time talking about gamma and can't see a consensus on what is considered "high" gamma and what is considered "low" gamma. Experts' opinions seem to differ, or they get mixed up, when talking about gamma. I have calibrated several displays over the last year and still find myself being caught out. I am of the opinion that 2.4 is "lower" than 2.2, but I am willing to be corrected.

So, to keep it simple, is a gamma value of 2.2 higher or lower than a gamma value of 2.4?
This will help

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post #10 of 21 Unread 04-09-2017, 11:19 PM
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Both videos posted by randal_r are basically marketing fluff from a guy without an understanding of the gamma concept at all (apparently he has founded the ISF - but thats on another page), they offer no real insights - present concepts wrong, and mainly just talk about how you as a salesperson could sell something to guys driving Ferraris, or misscalibrate a TV - so you spouse likes it.

They sell viewers on the same outdated notion, that you choose gamma based on your roomlighting setting which is bordering on "not true" since about three years - and basically showing at every point, that that guy is "winging it" without ANY understanding of the matter.

The only reason those videos are picked to be shared here, is because of that guys name.

The only educational purpose of these videos is to once and for all show, that the ISF was created as an upsell arm of TV retailers to make more money. And thats where the head of the orgnaisation went and ended up mentally.

Not recommended.

On topic - no real "standard" as far as use of word conventions goes. 2.4 is "lower in overall brightness" (but thats relative to what you are aiming for - if your current TV can output 700-1000 nits, and you are aiming for 120, or even 300 (with 180 as the point where it stops being reasonable for SDR content indoors and 500 being the point where it stops being reasonable even watching TV in the midday sun in your garden) - you will still reach it with 2.4 no problem whatsoever) but higher numerically.
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post #11 of 21 Unread 04-10-2017, 06:31 AM
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Greetings again,

I am glad to see you are still in fine form.

The reasons I submitted the videos is for the explanation as to Gamma selection in relationship environmental conditions. Not ever having conversed with the individual who posed the question on Gamma, I felt that the videos might give him a greater insight on the subject. Presenting images of various Gamma settings from a waveform monitor and how it effects the overall image would only serve to confuse the matter and would be of little value to the questioner. This question was answered very well by others. It is said that any question is like a multi-faceted diamond and each facet is just a different perspective and since the question was already answered I merely shed light onto a different facet.

I noted that your posting was one of criticism but you failed to enlighten us with any hard facts on the subject of Gamma. To keep it with in the realms of reachability focus on REC-709, since it can be argued the the newer displays are those of an extra large gamut with enhanced contrast features but have no real reachable standards. We know they can reach the REC-709 standard but fail to reach the REC-2020 standard. I look forward to your future postings of facts on the subject of Gamma.

As for your comments of Joel Silvers is unfounded, the video calibration organizations strive for changes to be made by the manufactures and the extended controls that are now available on displays are by their efforts. The biggest problems with the manufactures is that they listen too much to accountants and have blindly adopted their mindset. It is said that "Accountants sacrifice the dollars of tomorrow on the alter of profit for the pennies of today". Therefore they are resistant to adding new features out of fear for the bottom line. I noticed that you failed to comment on THX or Joe Kane, both have contributed more then you can imagine.

Since I have been criticized in the past by individuals such as yourself of lecturing, I will end this post and wait for the FACTS on the subject of Gamma.
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post #12 of 21 Unread 04-10-2017, 08:53 AM
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Uhhh, I take it you two "know" each other. Heh.

EOTF (Gamma) can be objective (matching the grading display & ambient lighting) or subjective. In the end it's up to the user.

If you go with subjective then whatever choice the person makes is correct.

Also from personal experience 500cd/m2 w/ a 2.4 power law curve is not bright enough for SDR content when the midday sun glaring through my front windows onto the screen. Heck even with a power law curve of 1.6 it's still hard to see darker details through the reflections.
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post #13 of 21 Unread 04-10-2017, 11:59 AM
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Originally Posted by nodixe View Post
Just thought I'd add my opinion as well. Gamma refers to how fast or slow a display comes out of black. Basically how many steps to get out of black between 0 and 100% on a 21pt grayscale. The higher the gamma the more steps out of black. That's why we percieve a dimmer picture but the peak luminance doesn't change (ideally).

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Sorry, but there really aren't any more steps. It's just that the luminance the display produces is higher or lower for each step (except for Black and 100% White) depending the gamma curve used.

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post #14 of 21 Unread 04-11-2017, 02:31 AM
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Originally Posted by randal_r View Post
Greetings again,

I am glad to see you are still in fine form.

The reasons I submitted the videos is for the explanation as to Gamma selection in relationship environmental conditions.
Hi.

Thats definitely a topic in those two videos (I've coincidently watched before), but it approaches it from a sales guys perspective, thats stuck in the sixties.

Basically the "theory" Joe silver offers is, that you should sacrifice everything and anything, just to "impress, fit the situation, or just because it will leave you with a satisfied spouse [his alegories, not mine]".

If you have to put your TV in vivid mode - with PL Gamma 1.9, then just do it, because you want to sell something to a guy driving a Ferrari - or to satisfy your white wine drinking wife and her girlfriends [his mental images for this argument, not mine].

Thats a position. It might even have been a valid one back in the 60s, you being a sales rep at one of those retailers that isn't around anymore - but this coming from the head of the group that is "in control of assessing and establishing color accuracy" - is just too much. And thats before he starts his sales pitch on how to "impress the customer".

F*ck this. Don't give his behavior accolades instead - because you are impressed by a name or a reputation.

The larger issue is, that while this explanation might have been valid 50 years ago - it isn't anymore.

Max. brightness (indoor vs. outdoor "compatible") isn't tied to gamma anymore - hardly at all. The difference in light output between 2.2 and 2.4 gamma on an end user device might be about 30nits on an average scene - on a screen targeting 100 nits. Let it be 50 (it isn't but let it be) - the difference between what SDR content is "meant to be looked at" or "mastered" is 48-72 nits (cinema depending on the projector in use) and 100-120 nits "at home" - to 300-500 nits (full screen white) capability of TVs today.

The "idea" that you'd have to switch to PL Gamma of 1.9 or 2.2 to "get a little more brightness for conventional use" just isn't true anymore -

but thats not my main issue with this freaking sales guy. If you switch from one gamma to another one - you impact color accuracy. You impact look, presentation, directors intent.

Something the ISF was "guarding" by their own volition - but then, two years ago, the industry game along and bought them out, telling them, that the new idea they should be selling was "individual capabilties of max brightness, and max contrast" on a TV.

And the agility with which that freaking guy bowed down to manufacturer interests and went on telling calibrators to sell peak capability (for no real reason - the content for that has yet to be "imagined" and the "standard is in transition") instead of accuracy is astonishing.

As a fact - that guy has no idea - "what gamma to use" in what "room situation" - if he can't escape the question and instead talk about "what brings 30 more, and why that would be beneficial" (in practice it isn't and 30 nits are jumpchange by now). Because his crew, and the industry were instrumental in NOT defining it.

So now the ISF is actively participating in populating the myth that color accuracy is a thing of the past, not important - and if you just wan't to switch to vivid - go ahead, do it - why not. If you can sell more TVs that way - to an unassuming audience....

That sale pitch is in both of those videos. That misrepresentation of the actual role of "the gamma curve" is in both of those videos.

Why I don't know. That guy went on a stage, in front of all "his" calibrators, to talk about gamma and instead talked sales pitches and Ferraris.

Explain that to me (guy - not necessarily you personally).

Joel Silver is my personification and picturepiece of whats so damningly wrong with this industry.

The next thing is, that you - as a manufacturer (lets take LG for example) can happily invite five of those "calibrators" to a product presentation and mess around with "their own" equipment - because in the end you can be absolutely sure - that those guys will come out of that "opportunity" talking about MAJOR IMPROVEMENTS IN OUT OF BLACK PERFORMANCE (something that wasn't on their radar before) - but none of those jokesters will have measured the gamma curve thats responsible for that to begin with.

Then have them talk about "great color accuracy" - because of the new LUT capabilities - but not offer up ANY measurement values on color accuracy. (Just out of interest - compared to what gamma?)

If all ISF calibrators are capable of today is to repeat freaking marketing messages, why do you need them? If they shed the "scientific" principles their discipline is based on at the suggestion of industry initiatives - what purpose do they still serve?

Watch the videos above to get those answers. Upsell. For retailers. Be a money stream for creators of proprietory software solutions. Be part of a feel good factor that suggest "premium" without meaning anything...

Other than that..., I'd say ask Joel Silver - but no, don't...

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Originally Posted by Quad5Ny View Post
EOTF (Gamma) can be objective (matching the grading display & ambient lighting) or subjective. In the end it's up to the user.
Then thats the question of the day. Why?

If the difference between the two is about 30nits in general and thats qualified as "the improvement you get choosing one above the other" - but then at the same time that Joel Silver can argue about just calibrating a personal home theatre (projectors) to 140nits - no problem, just because the capabilities are now there. Also on the basis of customer preference.

Its a joke.

And if 600 nit are available - go with that, why don't you - capability is beautiful.

And at the same time he will still happily suggest to use 2.2 over 2.4 because it just brings a little more "umpf" to that 600 nits picture - that has adhere to no standard whatsoever - but the creator of the calibrators union happily will put on display and "calibrate" (for money.. for his customers?

Again f*ck this. Why?

Color differences between 2.2 and 2.4 can well exceed a dE of 3, 5 or even 10 (not useful as a comparative measure, because its not linear), just because of luminance (color brightnes) - which is defined by gamma, and the target brightness you want to reach.

Color differences between the 2.2 and 2.4 "target" produce visually different results in any case - so why can't the head of the ISF answer the question - which one to adhere to? (Answer - because it isn't defined in the standard, and they changed the gamma to target midway of the "Blueray" (SDR) product cycle - and the new quasi standard (bt1886) is a Joke in its own right - because it serves the purpose to be two things to different people. (can be either PLG 2.4 or PLG 2.2 at high ires with a "black compensation" of around Gamma 1.8 to 1.9 at low IREs depending on an ARTIFICIAL VALUE (having NOTHING to do with lighting conditions - on modern TVs) - namely the measured black level of your device > resulting in starkly different visual images that are pronounced "virtually identical", not based on any perceptual science, but on a mathematical curve whose math is "beautiful" because its so simple - it doesn't even account for any perceptual weighing.
(So how on earth does it know the importance a certain blacklevel. At unknown room lighting conditions. - Nevertheless - it visually alters color representation - based on the gamma targets it "suggests" alone.)

Some of those are complicated words - but the concepts are fairly simple - try to read up on them and make up your own mind. Preferably before you embark on a "career" in this field (= buy "training" and "certificates"). From that guy.

I didn't by the way. So this is not some strange "fall out" this is legitimate anger, because those guys abandoned their purpose, and rather would talk about sales pitches, than technical concepts - in front of cameras, on youtube. But still under the guise of talking about technical concepts.

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post #16 of 21 Unread 04-11-2017, 10:01 AM
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Hi harlekin,

I reviewed both videos while keeping your comments in mind. You seem to want to convey that anyone and everyone who takes the ISF course is more or less taking a marketing course; this is not true. An explanation of any particular subject will also be subjected to the knowledge base of the individual. A business man will refer it to the perspective of businesses, a carpenter from a building perspective, a lawyer from a legalistic perspective, and so on and so on. The fact that Joel Silver has a perspective that you do not like does not negate the fact that the knowledge of the subject he is trying to convey is of no value.

In keeping this simple, is not gamma the adjustment of how quickly black goes to white or dark to bright? Is not the projected luminance plotting a reflection of the gamma? Set a gamma setting in your calibration software and observe the projected plot, now change it to another setting and the plot will change again. If you also note the Target"Y" values will will also change from one setting to another. I would ask you to pick up any DVD you might own an show me the gamma setting of that medium. There is no "One Size Fits All", for if there was we would not need the function of Gamma at all. One thing I have you do for us all is enlighten us as to what gamma is and how it should properly be used.

Although not everyone who will take a video calibration course will enter it in a professional capacity but at one point in time almost everyone of them will calibrate a display for another individual. After it is all said and done the end product is end user satisfaction. There is nothing more destructive than an unsatisfied end user. Since many individuals take these courses as a possibility of going into a possible business it is not unreasonable for the educator to focus the teaching for that particular end.

You seem to have an underlying anger and/or hatred within you and you focus on this industry as a tool for lashing out. This was true in your past postings and seems to have carried over into the present. You offer no data to support your statements. It was my hope that you would have grasped the wisdom that was offed you once before, "You can't push a rope". Stop trying to change what you can't. Maybe if you educate without ranting then maybe more will adopt you view points. I am sure all of us have something we wish we could change but your approach is self-destructive. Maybe if you had taken one of these courses you might feel different about them.
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Quote:
Originally Posted by Rolls-Royce View Post
Sorry, but there really aren't any more steps. It's just that the luminance the display produces is higher or lower for each step (except for Black and 100% White) depending the gamma curve used.
You are correct. There are a set number of electrical signals used for pixel brightness (Does 10 bit display have more steps/signals than 8 bit?) and these do not increase. I should have said more of the 21 steps are used to come out of black but I was trying to make it simple (no eotf) and relevant to his question but I'm unsure I succeeded at either. What I meant to get across was the higher gamma number gamma (2.4) can still reach the same white 'brightness' but in general, has a perceptually darker picture than then a lower (2.2) gamma. Also I wanted to suggest watching a grayscale ramp while changing gamma presets to see what's goin on. Anyway thanks for correcting me....

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post #18 of 21 Unread 04-15-2017, 12:36 PM
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I'm not trying to convey - that everyone who has taken an ISF course has nefarious reasons or anything along those lines.

I'm saying that in those videos Joels Silver - the head iSF representitive makes claims that are non factual, doesn't clue in on the point two times on purpose - to proceed to then not give you the actual statement, but rather a previously prepared marketing pitch on "why you'd need his calibration services".

I'm also saying that this guy had the guts to get on stage at a conference proclaiming to talk about gamma, and then proceeded to give a pure marketing speech centered on "how to upsell an unknowing customer". In the past - and in the future.


The two videos together are as close to being a display of practical fraud - not because the guy doesn't know what he is talking about in depth (and he doesn't) - but because of how he suggest calibrators should behave to "sell" their services.
-

Also - I know this is 2017 and everyone likes to live more and more in their own personal bubble and decide on if they'd consider facts based on "how much they like them" - but this stuff - sadly is factual.

If someone gives a marketing presentation instead of a tech talk about a subject he is supposed to talk about - and there is video of it - you just don't get to excuse it with "that guy just had a different perspective".

If someone doesn't show any understanding about how luminance affects color representation, then proceeds to sell you and your "customers" on "vivid mode for when the sun shines", then tells you you should use it because peak brightness is beautiful - all the wile never mentioning gamma at all, or how his "suggestions" impact every picture characteristic including, but not limited to gamma - that guy has perfectly shown that he never started to look into the topics he is giving public talks about.

In addition - I've watched other ISF events that are littered with wrong statements and inaccurate use of tech terms in the past -


(Look out for the Interview portion with one of "the most well regarded" people in the scene - and watch it with a critical mindset - might not be in this video (which is full of inaccuracies as well), but its part of this "series".)

So if you'd pin me down to give you an oversimplistic characterisation of the ISF "as they represent themselves in public videos" -

they are a bunch of pseudoscientific "clubmembers" that love to bamboosle you with "tech talk" they - more ofteh than not don't apply correctly - with the intended goal to upsell members of the public into buying their services, or paying an additional fee to a retailer that has contracted with a charter member of their operation.

I wen't into this field with an open mind, and learned from various sources openly available to the public - I was shocked and disgusted to see those videos on display - and I won't allow them to be handed on as "good advice" just because of some "confidence play" ("I know that guy's name and reputation!").

If you watch the entire 2014 HDTV shootout series - somewhere in the videos, their calibrators admit, that they were using different gamma targets, because they didn't calibrate gamma. (WHAT?") They also didn't really measure it, because Calman didn't tell them to.
But they were very excited to show you low dE numbers on Greyscale towards a target they never properly defined.

Looking at the TVs in the room - some of them have obvious color tints - that can't be explained away with off axis viewing angles (because they've set up several shots - you can use to disproove their claim) - but they try to use that excuse nevertheless.

The remaining 80% of that event is a sales presentation as well - complete with "sign me up" opportunities after every talk.

edit: Linked the wrong year of the shootout videos. Fixed now.

Last edited by harlekin; 04-15-2017 at 02:48 PM.
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post #19 of 21 Unread 04-15-2017, 03:01 PM
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Also - the guy is a repeat offender.

Starting a talk about TV calibration with a slide that reads:

Sharp Sakai City - $11 Billion and
Panasonic Amagasaki - $2.11 Billion -

then taking the time to emphasice just how state of the art the facilities are nowadays that those TVs get prododuced in - is NOT, i repeat NOT the job of someone who should be for the lack of a better word a "consumer advocate".

That guy is a marketing shill. And after that presentation you had Robert Heron talking about the factories for the two following years (if my memory serves me well - please factcheck before you quote me here.. ), for no good reason. So apparently it works.

edit: Also great audio guys - real stellar, you are the pros. Also thanks for confirming it on video, just how great you think that audio is. Basically perfect.

edit: This video, is such an utter disgrace - that I challenge you as someone with an IQ in the 90s range or higher to watch it in its entirety without pausing and then not tell me, that you have to hate this guy - whose job seems to be to trick the public in nodding their heads to consequitively more and more outrageous A-B comparisons that make no sense considering what hes proclaiming to talk about.

And then again - if thats the BEST the ISF can produce... Questions arise.

Last edited by harlekin; 04-15-2017 at 03:29 PM.
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Originally Posted by holdemphil View Post
I have read many articles and posts over the time talking about gamma and can't see a consensus on what is considered "high" gamma and what is considered "low" gamma. Experts' opinions seem to differ, or they get mixed up, when talking about gamma. I have calibrated several displays over the last year and still find myself being caught out. I am of the opinion that 2.4 is "lower" than 2.2, but I am willing to be corrected.

So, to keep it simple, is a gamma value of 2.2 higher or lower than a gamma value of 2.4?
Hi holdemphil,

I regret that this thread was hi-jacked. Your question on Gamma has been answered by others within this thread; The lower the Gamma number the brighter the image. Also keep in mind that a Gamma of 1.8 will not clip the anything below reference white nor will Gamma 2.4 clip the blacks. The setting of these values are defined when setting Contrast & Brightness. The function of Gamma will only manipulate everything in between.

If I could give you any advise that I thought would serve you the best, that would be to take a weeks time and research "How to read a waveform monitor and vectroscope". Upon completion you will have an excellent understanding of Luma, Chroma, Gamma and how it is utilized by colorists and broadcasting technicians. There are some excellent tutorials on Youtube where you can see the effects of an adjustment verses just reading about it. Good luck.


To harlekin,

It would be great if we could set up displays that were completely linear but how do you you propose that the issue of the cost of replacing equipment around the world to comply with the linear standard? How are you going to address the issue of legacy material? Do we just discard it? In that sense we are throwing away our history.

Too keep this as simplistic as possible, Gamma deals with how fast an image moves from black to white. The issue of Gamma (in video), existed long before the issue of color or the correction of color. My point of reference is pre-1953 when black and white televisions where only available. The only issue one had to deal with was Luma. (Luma is the luminance of black and white with the factor of Gamma introduced to it). Broadcaster would add a Gamma factor between 1~2; as it made the image appear better. After 1953, color was introduced. This introduced the Chroma signal which piggy backed on the Luma signal. Any display that was colored based could read and process the chroma signal and the Luma but those that where strictly black and white processed only the luma. At this point the legacy issue began.

Ever since 1953, all color based displays operate internally as RGB based displays. Since the the bandwidth of an RGB signal would be too great for broadcasting, the engineers stripped away the green component of the signal to shrink the overall signal to a level that was more usable. Since they had the values from the Luma portion and the Red value as well as the Blue value, it was easy to mathematically calculate the Green value; hence Y' PrPb. (Note that the proper expression of Luminance is changed to Luma and is denoted as Y' and not Y as the apostrophe shows that a Gamma factor has been added). An issue that still exists today is the errors that occur in the conversion process. Since the Y'UV, Y'PrPb or the Y'CrCb has a greater colorspace then the RGB colorspace, RGB Gamut errors can exist when converting.

The best way to see the effects of Gamma is to observe the video material while utilizing a waveform monitor. One then can see how the brightness or darkness of the image can be shewed. Colorists utilize this when making adjustments from one scene to another. Since the Chroma signal is piggy backed on the Luma portion, it somewhat follows the Luma's lead. Due to fact that Chroma and Luma can be separated a colortist will view and adjust the Chroma via a vectroscope.

(The above was not mentioned for your benefit but for any newbie who might be trying to follow along. I also apologized for the extremely quick overview, as chapters could be stated on the subject and trying to condense it into a paragraph not as easy as I thought)

With regards to the "Color Tracking, Color Fidelity & Gamma". In the first portion, the mentioning of discoloration within the grayscale. This introduces a pet peeve that I have. This could stems to improperly setting contrast and brightness. The 3 Rules for setting contrast should be abolished as they do not work and only serve to create more issues then they solve. If any one would like to debate and discuss this further create a new thread and I'm there but not on this one.

I do not wish to debate what seems to be personal opinions you have regarding the individuals within the videos or their technical expertise. You make statements that the individuals in the videos do not understand the science of Gamma, which implies that you are more enlightened. Yet, in all your postings I have failed to see any facts or data presented by you to support your opinions. By all appearances your posting are nothing more than a Bashing session. It is obvious of your opinions of these individuals in the videos, so please enlighten us the the secrets and the sciences of Gamma. (preferably on a different thread).
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Originally Posted by randal_r View Post
Hi holdemphil,

I regret that this thread was hi-jacked. Your question on Gamma has been answered by others within this thread; The lower the Gamma number the brighter the image. Also keep in mind that a Gamma of 1.8 will not clip the anything below reference white nor will Gamma 2.4 clip the blacks. The setting of these values are defined when setting Contrast & Brightness. The function of Gamma will only manipulate everything in between.

If I could give you any advise that I thought would serve you the best, that would be to take a weeks time and research "How to read a waveform monitor and vectroscope". Upon completion you will have an excellent understanding of Luma, Chroma, Gamma and how it is utilized by colorists and broadcasting technicians. There are some excellent tutorials on Youtube where you can see the effects of an adjustment verses just reading about it. Good luck.
Hi randal,

You're right, my question has been answered. It was never about how different gamma levels appear though, rather how to label them correctly in discussions. I have been swayed by the explanations on why you should refer to them as higher/lower based on their numerical value rather than light output. 2.4 is now a high gamma in this household..

I will definitely spend some time looking at "How to read a waveform monitor and vectroscope".

Thanks again, all.
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