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post #61 of 180 Old 07-03-2019, 10:03 AM - Thread Starter
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Quote:
Originally Posted by Dominic Chan View Post
Most people would aim for lower, to allow for the HDR highlights.

Interesting, so somewhere between 40 & 50 nits would give some sort of HDR higlights, I guess its going to be trial and error.
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post #62 of 180 Old 07-03-2019, 10:14 AM
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Originally Posted by AdamAttewell View Post
Interesting, so somewhere between 40 & 50 nits would give some sort of HDR higlights, I guess its going to be trial and error.
The actual ST.2084 uses about 100 nits for diffuse white, and everything above it (up to 10,000 nits) for highlights. Tone mapping squeezes the highlights to a much narrower range - whatever you have between the “scaled reference white” and the peak white of your display.
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post #63 of 180 Old 07-03-2019, 10:23 AM
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Quote:
Originally Posted by Dominic Chan View Post
The actual ST.2084 uses about 100 nits for diffuse white, and everything above it (up to 10,000 nits) for highlights. Tone mapping squeezes the highlights to a much narrower range - whatever you have between the “scaled reference white” and the peak white of your display.
ST 2084 does not define defuse white. The ITU is now recommending 200 nits diffuse white for HDR broadcasting (BT.2100)
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post #64 of 180 Old 07-03-2019, 11:41 AM - Thread Starter
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Does this effect me as I will be using BT 2390 after using ST 2084 for the two point grayscale?

All these gamma formulas make my head spin


I must be doing something wrong here as there is no way I can match this luminance curve with the gamma controls.

This is before I adjusted the gamma controls

This is after maxing them out


I am using BT 2390 with a white level of 40 nits.

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post #65 of 180 Old 07-03-2019, 01:27 PM
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Quote:
Originally Posted by AdamAttewell View Post
I am using BT 2390 with a white level of 40 nits.
I might have misled you earlier with CalMAN’s definition of “white level”. Hopefully Tyler will explain it correctly.

Looks like it’s being used as the peak luminance for ST.2390.
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Last edited by Dominic Chan; 07-03-2019 at 01:30 PM.
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post #66 of 180 Old 07-03-2019, 02:10 PM
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Projector Calibration (6040UB) - Second Look

Quote:
Originally Posted by AdamAttewell View Post
Does this effect me as I will be using BT 2390 after using ST 2084 for the two point grayscale?

All these gamma formulas make my head spin


I must be doing something wrong here as there is no way I can match this luminance curve with the gamma controls.

This is before I adjusted the gamma controls

This is after maxing them out


I am using BT 2390 with a white level of 40 nits.


The white level needs to be set to whatever the peak luminance of your display is. Which looks like it is around 133 nits.
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post #67 of 180 Old 07-03-2019, 04:59 PM - Thread Starter
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@Dominic Chan No worries, like you said you have never used CalMAN so grain of salt & all that

Just thanks again for all the info, help & time you have given. I would be lost without it.

I will set the white level at 133 nits tomorrow & see where it takes me.
One other question, what is the reason for adjusting the two point grayscale controls the gamma formula ST 2084 & then switching to BT 2390?

Should I not be using BT 2390 when adjusting the two point grayscale controls?

@WiFi-Spy is it recommended to do this in CalMAN? I dont know if HCFR implements things differently & the workflow I am following is for HCFR.

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post #68 of 180 Old 07-03-2019, 05:31 PM
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Originally Posted by AdamAttewell View Post
Should I not be using BT 2390 when adjusting the two point grayscale controls?
The objective of the 2-pt adjustment is to achieve D65 over the entire range of input values, using 20/80 or 30/70 as “representative” points. It does not involve adjustments of the luminance to match a specific gamma or EOTF.
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post #69 of 180 Old 07-03-2019, 06:13 PM - Thread Starter
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Quote:
Originally Posted by Dominic Chan View Post
The objective of the 2-pt adjustment is to achieve D65 over the entire range of input values, using 20/80 or 30/70 as “representative” points. It does not involve adjustments of the luminance to match a specific gamma or EOTF.

So technically it should not matter if I use BT 2390 or ST 2084 when adjusting the two point controls?


Its just when I switch from ST 2084 to BT 2390 the error of certain grayscale points increases.
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post #70 of 180 Old 07-03-2019, 06:20 PM
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Originally Posted by AdamAttewell View Post
So technically it should not matter if I use BT 2390 or ST 2084 when adjusting the two point controls?


Its just when I switch from ST 2084 to BT 2390 the error of certain grayscale points increases.
Does the error include the luminance component?

Many of the adjustments involve iterations as they affect one another. Doesn’t the CalMAN workflow specify the sequence of adjustments?
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post #71 of 180 Old 07-04-2019, 02:28 AM - Thread Starter
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Quote:
Originally Posted by Dominic Chan View Post
Does the error include the luminance component?

Many of the adjustments involve iterations as they affect one another. Doesn’t the CalMAN workflow specify the sequence of adjustments?
CalMAN does specify the sequence of adjustments like this:


When you load the HDR workflow it sets the gamma formula to ST2084 but I am unsure if I should be using BT 2390 from the start.

@WiFi-Spy Can you confirm that I should be using BT 2390 from the beginning of the HDR workflow.

I am not sure if the error includes luminance, I would guess not seeing as on the screen grabs above it says "RGB Balance without Luminance" & thoses are the errors I am looking at.

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post #72 of 180 Old 07-04-2019, 08:05 AM - Thread Starter
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So I started fresh on the Bright Cinema picture mode, I used BT2390 from start to finish. I measured 137 nits at 100% white on my first grayscale sweep so I used that as the white level.


Here is the grayscale after adjusting the two point controls at 20% & 80%

After adjusting the 2 point controls I lost about 8 nits so I dont know if I should have changed the white level to 129 nits before adjusting the gamma controls.

After adjusting the gamma controls alone I could not get close to matching the EOTF curve.



So I ended up maxing out the contrast control to get the curve close & then used the gamma controls to bring the low end back into line



I then moved onto the CMS which started off like this.



After adjustments I could only manage this.



So I went back to the grayscale & remeasured & got this.



So I adjusted the gamma controls again to bring things back into line.



Then back to the CMS & without any adjustment error was dramatically reduced.



I had another go at adjusting the CMS.



Then checked the grayscale again



So any good?
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post #73 of 180 Old 07-04-2019, 09:10 AM
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Quote:
Originally Posted by AdamAttewell View Post
So any good?
Greyscale and CMS look pretty good, but the EOTF shows very early clipping because you’re using such a high diffuse white level (82 nits at 50%).

The attached figure shows curves hard clipping at 1000 nits (75%) and 4000 nits (90%) with a scale factor of ~4; yours clips 60% (200 nits on the PQ curve).
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Last edited by Dominic Chan; 07-04-2019 at 09:58 AM.
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post #74 of 180 Old 07-04-2019, 10:09 AM - Thread Starter
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Quote:
Originally Posted by Dominic Chan View Post
Greyscale and CMS look pretty good, but the EOTF shows very early clipping because you’re using such a high diffuse white level (82 nits at 50%).

The attached figure shows curves hard clipping at 1000 nits (75%) and 4000 nits (90%) with a scale factor of ~4; yours clips 60% (200 nits on the PQ curve).
I mean I did what Tyler said & set the white level to the peak luminance of the display which seems to set where the EOTF curve rolls off.

I am not sure how I go about adjusting the EOTF target curve in CalMAN other that adjusting/increasing the white level like this.

No way I am hitting 700 nits

I guess there must be another way.

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post #75 of 180 Old 07-04-2019, 11:43 AM
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No way I am hitting 700 nits

I guess there must be another way.
Most other calibration packages apply a scale factor when calibrating HDR for projectors. This article refers to “screen offset” which seems to be equivalent.
https://professionalvideoalliance.co...ors-on-calman/
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post #76 of 180 Old 07-04-2019, 12:13 PM - Thread Starter
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Quote:
Originally Posted by Dominic Chan View Post
Most other calibration packages apply a scale factor when calibrating HDR for projectors. This article refers to “screen offset” which seems to be equivalent.
https://professionalvideoalliance.co...ors-on-calman/
Interesting link, I see he also mentions Tylers method too. So is this a matter of preference?

If I understand correctly to use the screen offset method I need to use ST 2084.

Then lets say the peak luminance of the display is 133 nits so divide this by 1000 you get 7.5 so round that up to 8.

I then use 8 as the Y value under the Screen Offset option.

I presume I just use the measured white level option instead of manually setting one?

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post #77 of 180 Old 07-04-2019, 02:04 PM - Thread Starter
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So take two with the offset applied correctly I still don't see any change in the EOTF curve
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post #78 of 180 Old 07-04-2019, 02:17 PM
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So take two with the offset applied correctly I still don't see any change in the EOTF curve
The way I understand it is that all the measurements will be multiplied by the "screen offset", which means you need to multiply the white level by 8 (i.e., use ~800 instead of ~100) for white level.

However, there are still two issue that I expect may happen if you use ST2084 without BT2390:
- Everything will still clip at 1000 nits (since that's what you use to the derive screen offset)
- A multiplier of 8 will make the overall picture fairly dim

In any case, you will find out whether that actually is the case.
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Last edited by Dominic Chan; 07-05-2019 at 06:01 AM.
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post #79 of 180 Old 07-04-2019, 04:15 PM - Thread Starter
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Originally Posted by Dominic Chan View Post
The way I understand it is that all the measurements will be multiplied by the "screen offset", which means you need to multiply the white level by 8 (i.e., use ~800 instead of ~100) for white level.

However, there are still two issue that I expect may happen if you use ST2084 without BT2390:
- Everything will still clip at 1000 nits (since that's what you use to the screen offset)
- A multiplier of 8 will make the overall picture fairly dim

In any case, you will find out whether that actually is the case.
I will give that a go but I agree I think it will be to dim.

Seems at this point it would be easier to use HCFR but I am pretty sure my Lumagen wont work as a pattern generator with it.



Plus having paid for CalMAN I would like to use it.
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post #80 of 180 Old 07-04-2019, 04:30 PM
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Plus having paid for CalMAN I would like to use it.
You can still use CalMAN. I would, however, use a lower screen offset (4 or 5), and also use BT2390 tone mapping.
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post #81 of 180 Old 07-04-2019, 05:11 PM - Thread Starter
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You can still use CalMAN. I would, however, use a lower screen offset (4 or 5), and also use BT2390 tone mapping.

Just so I understand, that's using BT 2390 with a screen offset of lets say 4 and a white level of 400 nits?


Or would I multiply the peak luminance of the display by 4? So 131 x 4 = 524 nits


I will give this a go tomorrow whichever is correct.

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post #82 of 180 Old 07-04-2019, 06:54 PM
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Just so I understand, that's using BT 2390 with a screen offset of lets say 4 and a white level of 400 nits?


Or would I multiply the peak luminance of the display by 4? So 131 x 4 = 542 nits


I will give this a go tomorrow whichever is correct.
The latter. I used 100 only because your latest plot showed 100.

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post #83 of 180 Old 07-05-2019, 08:24 AM - Thread Starter
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The latter. I used 100 only because your latest plot showed 100.

So BT 2390, Screen Offset = 4, White Level = 524 nits

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post #84 of 180 Old 07-05-2019, 08:55 AM
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So BT 2390, Screen Offset = 4, White Level = 524 nits
Yes, at least see what CalMAN gives you as a target curve.
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post #85 of 180 Old 07-05-2019, 09:03 AM - Thread Starter
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Yes, at least see what CalMAN gives you as a target curve.
What do you think?

Just struggling a little to understand how I am going to hit over 500 nits?

I know I can only get around 130 nits so the luminance error is going to massive? Or does this screen offset adjust the figures measured by the meter so I will be able to hit the target?

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post #86 of 180 Old 07-05-2019, 09:19 AM
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What do you think?
The target luminance curve looks as I expected. It soft clips at 1000 nits. If everything turns out you may want to have another curve for 4000 nits titles. I don’t remember if the Epson can hold more than one custom curve.

Quote:
Just struggling a little to understand how I am going to hit over 500 nits?

I know I can only get around 130 nits so the luminance error is going to massive? Or does this screen offset adjust the figures measured by the meter so I will be able to hit the target?

As I mentioned previously, I don’t know CalMAN so can’t answer this with certainty. However, based on that article the software will multiply the measurements with the scaling factor, so 125 nits will be treated as 500 nits when using a factor of 4.
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Last edited by Dominic Chan; 07-05-2019 at 09:28 AM.
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post #87 of 180 Old 07-05-2019, 09:27 AM - Thread Starter
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Originally Posted by Dominic Chan View Post
The target luminance curve looks as I expected. It soft clips at 1000 nits.
As I mentioned previously, I don’t know CalMAN so can’t answer this with certainty. However, based on that article the sofware will apply the scaling factor to the measurements.

OK I will give it a go and see where it takes me. I guess its going to be self explanatory if I cant get anywhere near to maching the curve.
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post #88 of 180 Old 07-05-2019, 10:50 AM - Thread Starter
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Quote:
Originally Posted by Dominic Chan View Post
The target luminance curve looks as I expected. It soft clips at 1000 nits. If everything turns out you may want to have another curve for 4000 nits titles. I don’t remember if the Epson can hold more than one custom curve.

As I mentioned previously, I don’t know CalMAN so can’t answer this with certainty. However, based on that article the software will multiply the measurements with the scaling factor, so 125 nits will be treated as 500 nits when using a factor of 4.
With those settings I cant get a decent grayscale it all, the two point controls seem to do nothing.

If I remove the screen offset things go back to normal & I get the usual result.

This is with the screen offset active.
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post #89 of 180 Old 07-05-2019, 11:19 AM - Thread Starter
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I decided to disable the screen offset when adjusting the two point controls & the enabled it again for adjusting the gamma controls.


This is the best I can do with maxing out the gamma & contrast controls. Still hard clipping at 60 nits if I am correct?
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post #90 of 180 Old 07-05-2019, 12:23 PM - Thread Starter
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Well I feel like a total dumbass now, I have the screen offset figure in the wrong y box

Was reading a little over on the HDR thread for the Epson & some people were disabling tone mapping when adjusting the CMS I presume this is not recommended.
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