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Discussion Starter · #1 · (Edited)
There have been some very good conversations past week or so on various other threads regards calibrating the Epson 5040/6040 for HDR.

These threads were...
http://www.avsforum.com/forum/68-di...ficial-epson-5040ub-6040ub-owners-thread.html
http://www.avsforum.com/forum/139-d...e-projector-display-calibration-software.html
http://www.avsforum.com/forum/139-display-calibration/2248138-official-chromapure-3-thread.html

In an effort not to swamp those threads and possibly take them off topic, I have created this one.

Update:
To save yourself reading loads of pages, the current process (WIP) is post 344
 

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Discussion Starter · #2 ·
@Dominic Chan

Continuing from the latest discussion, could you expand further on your current thinking of what diffuse white and peak brightness to try aim for for best of possible HDR experience with a projector?

My current understanding is that diffuse white is 100 nits, anything above this are spectral highlights. Naturally projectors are not as bright as screens that can hit 100's to 1000's of nits so we have a limited range for these.

Currently on my 5040 I'm getting the following using the 50%/100% Masciola pattern...
BC HDR1 med = 21 nits
BC HDR1 high = 27 nits
Dynamic HDR1 med = 39 nits
Dynamic HDR1 high = 54 nits

And the with 100%/100% pattern...
BC HDR1 Med = 116 nits
BC HDR1 high = 150 nits
Dynamic HDR1 med = 188 nits
Dynamic HDR1 high = 248 nits



Am I right in saying you are recommending for diffuse white to be 50 nits therefore leaving headroom for highlights? What I'm struggling with is how does the projector know that 50 is the diffuse white and maps from that?
 

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@Dominic Chan

Continuing from the latest discussion, could you expand further on your current thinking of what diffuse white and peak brightness to try aim for for best of possible HDR experience with a projector?


Am I right in saying you are recommending for diffuse white to be 50 nits therefore leaving headroom for highlights? What I'm struggling with is how does the projector know that 50 is the diffuse white and maps from that?
There is no HDR standard that applies to projectors, due to the much more limited peak luminance. What I suggested is to use half of the luminance, consistent with the SDR practice of calibrating to 50 nits white instead of 100 nits white.
This approach is similar to what Steve Shaw refers to as the "multifplier":
https://www.lightillusion.com/uhdtv.html
 

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There have been some very good conversations past week or so on various other threads regards calibrating the Epson 5040/6040 for HDR.

These threads were...
http://www.avsforum.com/forum/68-di...ficial-epson-5040ub-6040ub-owners-thread.html
http://www.avsforum.com/forum/139-d...e-projector-display-calibration-software.html
http://www.avsforum.com/forum/139-display-calibration/2248138-official-chromapure-3-thread.html

In an effort not to swamp those threads and possibly take them off topic, I have created this one.
That's a good idea, although the links can be more specific to a page or post where this topic was discussed. HCFR thread has close to 10,000 post!:)
 

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The 'Multiplier' approach is basically what Dolby use for their HDR projection based cinema, with their 103 nits projection configurations (I think it is 103 nits, without checking my data...).

To allow for different peak luminance we have a user definable multiplier within LightSpace to allow for user preferences.

(https://www.lightillusion.com/lut_manual.html#destination_colour_space)

We also have a user definable tone-map, as varying the rolls-off is key for getting the best final result, rather than just relying on the fixes time mapping of BT2390.

As they say, every little helps!

Steve
 

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Discussion Starter · #6 ·
Sorry folks, I'm still struggling with the concept, maybe just one of those days/weeks! Also can't see mention of multiplier in the https://www.lightillusion.com/uhdtv.html article.

Maybe I just need a better understanding of how the HDR works. If a UHD is created against 1000 nits, how does a projector with say 100 to 150 peak nits use this data? Lets say theres a scene where a bunch of pixels need 500 nits, does the projector just use max, so in essence for a scene with various high nit pixels eg 300, 400, and 500, a projector with 150 will just show max for all of them so there is no definition between them if that is the right word. I'm an engineer by trade and I can't let things go until I understand how they work, to my own detriment! Thanks for your patience.
 

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There is no HDR standard that applies to projectors, due to the much more limited peak luminance. What I suggested is to use half of the luminance, consistent with the SDR practice of calibrating to 50 nits white instead of 100 nits white.
This approach is similar to what Steve Shaw refers to as the "multifplier":
https://www.lightillusion.com/uhdtv.html
Thanks for creating this thread!

Dominic, I've been following your lead on how to approach this for the 5040ub and already I really like the results.

The attached chart shows how my gamma is tracking to the targets that Zoyd provided (with some small adjustments down to 138 nits). Picture looks very good now and I don't have the issue with HDR being too dark.

But as you'll see, the main challenge is that my luminance is too low from 50% to 70%. Gamma settings are completely maxed out in these ranges. I can get these closer to the targets by increasing the contrast (currently set very low at 20) but then I start to see the whites getting crushed.

I used Ryan's white clipping pattern to set contrast to clip at 1000 nits (this is how I arrived at a low contrast of 20). Again, if I increase it I do start to see whites getting crushed.

Is this the right way to set contrast for HDR, knowing what I am trying to do with the 5040?

Any other suggestions to improve these results?
 

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But as you'll see, the main challenge is that my luminance is too low from 50% to 70%. Gamma settings are completely maxed out in these ranges. I can get these closer to the targets by increasing the contrast (currently set very low at 20) but then I start to see the whites getting crushed.

I used Ryan's white clipping pattern to set contrast to clip at 1000 nits (this is how I arrived at a low contrast of 20). Again, if I increase it I do start to see whites getting crushed.

Is this the right way to set contrast for HDR, knowing what I am trying to do with the 5040?

Any other suggestions to improve these results?
I was able to get pretty close to the target curve (dotted yellow line) by keeping Contrast at 50, and reducing clipping using the top gamma control point. The target curve is for contents mastered on 1000-nit displays, but with a multiplier of about 50%.
I don't have Masciola's patterns, so all adjustments are based on HCFR's internal patterns and manually setting the mode to HDR1.
 

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I was able to get pretty close to the target curve (dotted yellow line) by keeping Contrast at 50, and reducing the top gamma control point. The target curve is for contents mastered on 1000-nit displays, but with a multiplier of about 50%..
I don't have Masciola's patterns, so all adjustments are based on HCFR's internal patterns and manually setting the mode to HDR1.
That's great. Very close. I did another round tonight and improved my results. I am getting it pretty close. HDR content is really looking good now. Thanks for suggesting this approach.

Are you able to share your custom gamma settings and how you were able to track the target so closely?
 

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Discussion Starter · #11 ·

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Discussion Starter · #12 ·
I was able to get pretty close to the target curve (dotted yellow line) by keeping Contrast at 50, and reducing clipping using the top gamma control point. The target curve is for contents mastered on 1000-nit displays, but with a multiplier of about 50%.
I don't have Masciola's patterns, so all adjustments are based on HCFR's internal patterns and manually setting the mode to HDR1.
What settings in HCFR do you use to show/draw your target curve?

Also are you using extended video range and superwhite?
 

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What settings in HCFR do you use to show/draw your target curve?
HCFR does not let one edit the target curve, so I had to come up with the following trick:
  1. Convert the BT.2390 tone mapping values posted by @zoyd, to 0-100% range. I use the 300_8000 version. (Unfortunately I forgot to use the "8-bit simulation" so there's a small error.
  2. Create a blank HCFR file using Simulated Sensor, setting all simulation errors to 0.
  3. Run the Gray Scale sweep, Primary and Secondary Colours, Saturation Sweeps.
  4. In the Grey Scale grid, turn on Editable Data, and change all the Y values to the BT.2390 values . I use the 1000 nits version but you can also ues the 4000 nits version.
  5. For the 100% stimulus, override the Y with the peak white you're actually getting (141 in my case). Select Yes to scale all measurement.
  6. Save the file and select it as Reference which you can use as the target for the real measurement.

I have attached the spreadsheet, the Reference chc, and my own measurements chc for those who want to try the approach.

Also are you using extended video range and superwhite?
No.
 

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The curve has a different shape for 141 nits max white compared to 300 max so I don't think that linear scaling will work.
Yes, I understand that. I've explained my rationale in a previous post
http://www.avsforum.com/forum/139-d...cial-chromapure-3-thread-44.html#post55174284

BTW, when I said "too bright", that is for projector in a completely dark room, where people calibrate to 50 nits rather than 100 nits SDR.
Hence I asked for a 300 nits curve rathan than a 141 nits curve.

I believe the JVC projector users are doing something similar for ST2084, although they don't seem to be aware of the tone mapping standard in BT.2390. LightSpace is also using something similar, in terms of aiming for a lower luminance.
 

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That's great. Very close. I did another round tonight and improved my results. I am getting it pretty close. HDR content is really looking good now. Thanks for suggesting this approach.

Are you able to share your custom gamma settings and how you were able to track the target so closely?
I can certainly post the gamma settings later for you to try.
However, I find it very hard to "read back" the custom gamma settings on the Epson projectors. It displays the setting while you're adjusting it, but does not display the value when you're done (unless you start changing it again). It only displays a graphical curve which is very "rough". Did I miss something?
 

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ok, you can compare to this curve where I have shifted the knee parameter to give you ~50 nits at 50% stimulus. (actual 59 nits for 1000 nit master, 41 nits 4000 nit master)
 

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I can certainly post the gamma settings later for you to try.
However, I find it very hard to "read back" the custom gamma settings on the Epson projectors. It displays the setting while you're adjusting it, but does not display the value when you're done (unless you start changing it again). It only displays a graphical curve which is very "rough". Did I miss something?
Yes, the gamma settings are a bit of a pain with the 5040. I don't need the exact settings. Maybe if you just take a picture of the curve for now. My situation is different given the luminance I get so I won't really be able to use your settings. I just wanted to see if it gave me any ideas.

Any tips on using the Epson gamma settings with HCFR? I think I read once that you set it up to do real-time adjustments.

A few other questions:
-
- I've just been experimenting for now to see if this approach actually produces a good result before spending too much time trying to get it precise. It seems as though it is going to work quite well. What is your opinion when looking at HDR content?


EDIT - I think Zoyd's new file addresses these questions. Thanks, Zoyd!

- When you scale the curve in HCFR (nice trick by the way), it also scales down the 0%. Wouldn't you want to leave 0% and maybe 5% at the original target? I can't hit 0.01 in my room.

- Looks like Zoyd verified that Ryan is actually using 10-bit codes rounded to whole numbers. So if I am using his disk, your scaled file is accurate, right?
 

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Yes, the gamma settings are a bit of a pain with the 5040. I don't need the exact settings. Maybe if you just take a picture of the curve for now. My situation is different given the luminance I get so I won't really be able to use your settings. I just wanted to see if it gave me any ideas.
I'll take a picture next time I turn on the projector (prefer not to cycle it on/off in a short time). From what I remember, I maxed out control C8 and turned down C9. C1 was untouched at 0, the others at slightly positive values.
[EDIT: Picture of Gamma Settings attached]

Any tips on using the Epson gamma settings with HCFR? I think I read once that you set it up to do real-time adjustments.
Once you've decided on a specific contrast setting, you can characterize the controls by running sweeps maxing out one control at a time while keeping all the others at default. I've posted the values previously, but that was for SDR.
An alternative for Epson projectors is to display a pattern and ask the projector to show you which control corresponds to that stimulus.
A few other questions:
- When you scale the curve in HCFR (nice trick by the way), it also scales down the 0%. Wouldn't you want to leave 0% and maybe 5% at the original target? I can't hit 0.01 in my room.
I requested zoyd to produce the curve for 300 nits peak and 8000:1 contrast ratio. The contrast ratio does not change when I scale down the values, so the black value after scaling is actually the right value I'm getting.
- I've just been experimenting for now to see if this approach actually produces a good result before spending too much time trying to get it precise. It seems as though it is going to work quite well. What is your opinion when looking at HDR content?
To be honest, it was really late last night when I finished so I did not even have any chance to watch real HDR content. However, as I mentioned previously, the default HDR1 curve was already very good with a diffuse white of 40 nits. This curve reduces the highlight clipping.
[EDIT: I watched X-Men Apocalypse and noticed some clipping of extreme highlight. Not sure if that movie was mastered on 4000 nits or 1000 nits display]

- Looks like Zoyd verified that Ryan is actually using 10-bit codes rounded to whole numbers. So if I am using his disk, your scaled file is accurate, right?
Yes.
 

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I'll take a picture next time I turn on the projector (prefer not to cycle it on/off in a short time). From what I remember, I maxed out control C8 and turned down C9. C1 was untouched at 0, the others at slightly positive values.

[EDIT: Picture of Gamma Settings attached]





Once you've decided on a specific contrast setting, you can characterize the controls by running sweeps maxing out one control at a time while keeping all the others at default. I've posted the values previously, but that was for SDR.

An alternative for Epson projectors is to display a pattern and ask the projector to show you which control corresponds to that stimulus.



I requested zoyd to produce the curve for 300 nits peak and 8000:1 contrast ratio. The contrast ratio does not change when I scale down the values, so the black value after scaling is actually the right value I'm getting.



To be honest, it was really late last night when I finished so I did not even have any chance to watch real HDR content. However, as I mentioned previously, the default HDR1 curve was already very good with a diffuse white of 40 nits. This curve reduces the highlight clipping.

[EDIT: I watched X-Men Apocalypse and noticed some clipping of extreme highlight. Not sure if that movie was mastered on 4000 nits or 1000 nits display]





Yes.

Do you think Ryan's white clipping pattern would help you?

I guess the ideal would be to have 2 calibrations - one for each mastering display

Thanks for posting the pic of the gamma settings.




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