helping a newbie understanding calibration and theory - AVS Forum
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post #1 of 16 Old 10-03-2013, 10:00 AM - Thread Starter
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Hi everyone,

I'm new to calibration but I got a used i1 pro + calman. I'm pretty serious about getting the theories in order and understanding the concepts behind the calibration (rather than just do it once and never know what i did).

I did a lot of research by reading these articles:
http://www.lightillusion.com/display_calibration.html
http://www.avsforum.com/t/852536/basic-guide-to-color-calibration-using-a-cms-updated-and-enhanced
http://www.hometheatershack.com/forums/video-calibration/54381-diy-display-calibration-via-calman.html

Using Chad's advice:
http://www.avsforum.com/t/1383050/gamma-vs-brightness#post_21409582

So what I gather for the steps of calibration:
1) adjust brightness and contrast
2) Set luminance
3) Adjust grayscale with 2pt balance
i) start with bias @ 20/30%
ii) then gain @ 80%
4) adjust CMS
5) adjust 10pt gray scale to level the gamma

I have several questions:
1) In the guide and forums, people mentioned not touching the "green" gain/bias settings. So would the "proper" way of adjusting this be subtracting/adding blue/red into the colour until i reach the target D65?

2) What does tint do? I remember a guide telling me that it shift the triangle around

3) Am I doing this right? are my steps to calibration logical?

4) I have a PN65D8000 that I attempted to calibrate. At 90%, the gamma drops. What should I do to correct for this? Do I leave it until the 10pt before adjusting it?

Thanks!
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post #2 of 16 Old 10-03-2013, 10:58 AM
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Originally Posted by goonx View Post

1) In the guide and forums, people mentioned not touching the "green" gain/bias settings. So would the "proper" way of adjusting this be subtracting/adding blue/red into the colour until i reach the target D65?

Green does dominate perceived luminance, but I don't follow that guideline. After adjusting contrast your gains will be aligned close to clipping. Because of that I only turn the gains down, since gains are typically individual R,G,B contrast controls.

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2) What does tint do? I remember a guide telling me that it shift the triangle around
Yes it effects yellow, magenta and cyan primarily and slides them clockwise or counter clockwise. Don't use tint if you have CMS. Don't touch tint till after you do white balance.

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3) Am I doing this right? are my steps to calibration logical?
so far so good.
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4) I have a PN65D8000 that I attempted to calibrate. At 90%, the gamma drops. What should I do to correct for this? Do I leave it until the 10pt before adjusting it?

Correct, pay no attention to gamma until you get to the 10 point. Also 90% is extremely sensitive if you are looking at gamma numbers, but the difference between 1.8 and 2.4 at 90% is a very small visible difference, so focus more on dE than gamma numbers.

Joel Barsotti
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post #3 of 16 Old 10-03-2013, 11:20 AM
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Greetings

You also have the option for professional level training and it doesn't have to cost that much. But if your time is worth little to you and it is about the exploration of how to do calibration ... rather than get to the end result faster and with more certainty ...

http://www.tlvexp.ca/tutorials/

Go here and watch these videos first ... then decide if you want to learn more about what you are doing ... with less mystery ... more certainty.

http://www.tlvexp.ca/2013/04/calibration-knowledge-challenge/

And if you think you already know what you are doing, then please take this quiz. It should be a snap. smile.gif

Regards

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The Video Calibration Education Hub - www.TLVEXP.com

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post #4 of 16 Old 10-03-2013, 11:39 AM - Thread Starter
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Thanks for the fast response. I am "feeling" it out but I'm a graduate student and I enjoy learning about the more academic side and the science behind the calibration. Funny, because i was just looking into your videos michael! I also saw that you're hosting a event in toronto at the end of the month.

Unfortunately being a graduate student means I don't have too much disposable income at the moment after the hardware/software investment. Maybe that will be an option for me later. I'm calibrating my parent's TV.

I "calibrated" this TV twice already but it was just shotgun and I had no idea what I was going other than following on-screen instructions. I'm slowing getting it.
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post #5 of 16 Old 10-03-2013, 11:53 AM
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Greetings

Well if you consider that the 7+ hour training series is now more thorough than any ISF class out there at less that 10% of what a class like that costs ... Sorry it can't be free.

If you want to sit in on that class ... same class being taught again and again over 2 to 3 days ... it can be arranged at a discount, but it will still be much more than the training videos.

regards

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post #6 of 16 Old 10-03-2013, 03:53 PM
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Originally Posted by goonx View Post

Unfortunately being a graduate student means I don't have too much disposable income at the moment after the hardware/software investment. Maybe that will be an option for me later. I'm calibrating my parent's TV.

similar position here smile.gif

also in toronto
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post #7 of 16 Old 10-03-2013, 05:45 PM - Thread Starter
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Hi,

So i'm having some difficulty with the greyscale

at the 2pt grey scale, I can get almost the D65 spot on. Then I move on to setting up my gamut which i can get pretty much spot on. When I adjust my gamma and 10pt greyscale, hell breaks loose!

I can't get the nice uniform gamma and the greyscale tracking is also very poor. Most of my greys are red-shifted and on my samsung, I'm already at the max of my 10pt settings.

What am I doing wrong?

Should I be doing the 10pt greyscale calibration first?

These are my steps for calibration:
1) adjust brightness and contrast
2) Set luminance
3) Adjust grayscale with 2pt balance
i) start with bias @ 20/30%
ii) then gain @ 100%
4) I got back and check the contrast and brightness again
5) adjust CMS
6) adjust 10pt gray scale to level the gamma

Using AVS 709 window patterns. Should I be using ABL ones for better results?
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post #8 of 16 Old 10-03-2013, 06:02 PM
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Quote:
Originally Posted by goonx View Post

Hi,

So i'm having some difficulty with the greyscale

at the 2pt grey scale, I can get almost the D65 spot on. Then I move on to setting up my gamut which i can get pretty much spot on. When I adjust my gamma and 10pt greyscale, hell breaks loose!

I can't get the nice uniform gamma and the greyscale tracking is also very poor. Most of my greys are red-shifted and on my samsung, I'm already at the max of my 10pt settings.

What am I doing wrong?

Should I be doing the 10pt greyscale calibration first?

These are my steps for calibration:
1) adjust brightness and contrast
2) Set luminance
3) Adjust grayscale with 2pt balance
i) start with bias @ 20/30%
ii) then gain @ 100%
4) I got back and check the contrast and brightness again
5) adjust CMS
6) adjust 10pt gray scale to level the gamma

Using AVS 709 window patterns. Should I be using ABL ones for better results?


For the D8000, the 10 point controls only match up with their designated ranges when the contrast control is higher than about 90. A lower contrast setting skews the 10 point ranges. Only experimenting will determine what range(s) is affected by a specific 10 point control.

Larry
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post #9 of 16 Old 10-03-2013, 09:29 PM - Thread Starter
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interesting, so you're saying the 10pt doesn't match the IRE ranges? My contrast was around 96.

My fl was 50 since I was tuning this for a bright room. Perhaps my contrast and fl settings are not allowing me to adjust to the proper gamma levels?

I've been setting my contrast by using AVS 709 contrast calibration image and setting it so that 235 stops flashing but 234 and above does. I believe is this correct?
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post #10 of 16 Old 10-03-2013, 09:46 PM
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Yeah you can set contrast too high and it'll start clipping so 90% or even 80% start to be as bright as 100%.

Before you even get to light level, you need to make sure you aren't causing clipping or discoloration with the contrast control.

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post #11 of 16 Old 10-03-2013, 11:53 PM
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Greetings

You should follow the three rules for setting contrast.

1. No clipping.
2. No discoloration
3. Eye fatigue considerations.

You should set the contrast to see as many bars as you can past 235 and not hard clip it at 235. One only starts to consider purposely clipping if there is insufficient light output if you don't clip. And even then, if discoloration creeps in, that is bothersome too. Whites look pink ... for instance.

regards

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The Video Calibration Education Hub - www.TLVEXP.com

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post #12 of 16 Old 10-04-2013, 01:05 PM - Thread Starter
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Originally Posted by Michael TLV View Post

Greetings

You should follow the three rules for setting contrast.

1. No clipping.
2. No discoloration
3. Eye fatigue considerations.

You should set the contrast to see as many bars as you can past 235 and not hard clip it at 235. One only starts to consider purposely clipping if there is insufficient light output if you don't clip. And even then, if discoloration creeps in, that is bothersome too. Whites look pink ... for instance.

regards

So from what i'm understanding is that contrast is not necessarily "right" when white is set as 235. I should satisfy the 3 "rules" first and I can have the 235 still flashing. If discolouration or clipping occurs, leave the contrast lower than the "235" level.

What would be the impact of not having the proper "white" level. Will this be fixed later when I calibrate the 10pt balance/gamma? Or this is something just to live with as an imperfection of the TV set/room conditions.
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post #13 of 16 Old 10-04-2013, 03:01 PM
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Originally Posted by goonx View Post

So from what i'm understanding is that contrast is not necessarily "right" when white is set as 235. I should satisfy the 3 "rules" first and I can have the 235 still flashing. If discolouration or clipping occurs, leave the contrast lower than the "235" level.

Technically you need to be able to resolve all the way up to 253 (254 is the background, 255 is not encodable on disc). 253 might be tough since it's so close to 254.

If you want to clip above 235, that is your prerogative, but it's not technically correct. You should at least always be weary of color shift above 235.



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What would be the impact of not having the proper "white" level. Will this be fixed later when I calibrate the 10pt balance/gamma? Or this is something just to live with as an imperfection of the TV set/room conditions.

If you clip, you'll end up with discolored highlights and coloration in your grayscale gradients. It will be very noticeable on any gradient white field which has become common in commercials. It's a very important step, you need to do it correctly.

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post #14 of 16 Old 10-05-2013, 02:06 PM - Thread Starter
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Technically you need to be able to resolve all the way up to 253 (254 is the background, 255 is not encodable on disc). 253 might be tough since it's so close to 254.

If you want to clip above 235, that is your prerogative, but it's not technically correct. You should at least always be weary of color shift above 235.
If you clip, you'll end up with discolored highlights and coloration in your grayscale gradients. It will be very noticeable on any gradient white field which has become common in commercials. It's a very important step, you need to do it correctly.

So for contrast, I just make sure that I can resolve all the bars on the AVS HD 709. Unlike brightness where i set it so that the 16th bar "disappears" into the background (and stops flashing).
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post #15 of 16 Old 10-05-2013, 03:32 PM
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So for contrast, I just make sure that I can resolve all the bars on the AVS HD 709. Unlike brightness where i set it so that the 16th bar "disappears" into the background (and stops flashing).

correct, but you also need to watch the shade as well. For instance, if red clips it will turn the top bar a blue shade which will make the rest of the grayscale appear pinkish. So if you see color shifts you need to continue to turn contrast down till changing the contrast a click down and a click up does not appear introduce a tint to the grayscale.

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post #16 of 16 Old 10-06-2013, 12:29 PM - Thread Starter
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Thanks Sotti,

your comments has been extremely helpful. I calibrated one of the displays and the result is day and night.

On my other set, i'm having a bit of difficulty with the "blue" CMS. Y seems to set a bit too high and if i increase the intensity of blue, light level is too high. Is there any tips where I can get my blues to be closer to reference?
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