topic Re: Q90R HDR highlight clipping in TV

Q90R HDR highlight clipping

FrankieSomeone — Fri, 03 Apr 2020 16:18:12 GMT

I only found a couple of posts on the internet mentioning this - when viewing HDR content the highlights get quite clipped, or rather they plateau and get squished at the top.

I have tried all kinds of calibrations and the only way to avoid this is to use the Movie profile with Local Dimming set to Low, which is not very good because it gets very dark and the panel won't dim at all unless it's entirely 100% black.

I believe this to be an intrinsic property of gamma st.2084 - some people might like it but I find very annoying that highlight details get erased, I thought one of the selling points of HDR was super bright reflections and highlights!

The pictures below are taken in Movie mode with Local Dimming set to High (it's the same with standard)
The picture without the clipping is what you see when you pop up the menu. It seems the highlights clip more the darker the overall screen is.

Come on Samsung, you can do better. At least give us a second gamma curve to choose from.

Re: Q90R HDR highlight clipping

FrankieSomeone — Sat, 04 Apr 2020 09:31:02 GMT

Update: the clipping is quite reduced by using the Standard profile and lowering contrast to about 25 - but with these settings, small bright things in very dark screens disappear completely (for reference, in the opening scene of Prisoner of Azkaban, the small bright window at the center of the screen becomes invisible until the WB logo appears)

Re: Q90R HDR highlight clipping

FrankieSomeone — Mon, 20 Apr 2020 07:31:52 GMT

Turns out Game Mode neutralises the tone mapping curve and keeps Local Dimming on. It creates a bit of blooming in dark scenes with bright objects and high contrast but no highlight details are lost.

Re: Q90R HDR highlight clipping

crisfreak — Sun, 28 Jun 2020 21:28:16 GMT

On my Q90R, I reduced the contrast setting to 42 to get no clipping

Re: Q90R HDR highlight clipping

btaiji — Sat, 11 Jul 2020 03:23:22 GMT

I AM so angry about this issue.

Samsung must solve this problem! Shame on you!

I hope my setting would help.

Backlight 50

Brightness +3 ~ +5 : only works on dark scene

Contrast 50

Local Dimming : Low

Contrast Enhancer : High

Re: Q90R HDR highlight clipping

btaiji — Sat, 11 Jul 2020 03:37:01 GMT

https://youtu.be/_cgmVElC018?t=120

Samsung's 2020 8K model Q900T has the same issue.

Re: Q90R HDR highlight clipping

FrankieSomeone — Fri, 24 Jul 2020 07:46:16 GMT

Thank you! That's exactly what I'm talking about. Happy to see someone else calling this out.

Re: Q90R HDR highlight clipping

btaiji — Fri, 24 Jul 2020 11:40:51 GMT

I will post about this issue on Korean AV community.

I'm Korean, so i wish some samsung-man will see my post.

I'll share the post here when I ready.

You might understand it by translator

Re: Q90R HDR highlight clipping

btaiji — Fri, 31 Jul 2020 02:04:02 GMT

BTW

Same problem occurs on 2020 4K QLED

I tested Q95T. It also clips highlight!!

Re: Q90R HDR highlight clipping

btaiji — Fri, 31 Jul 2020 02:04:43 GMT

I posted an article!!

https://dvdprime.com/g2/bbs/board.php?bo_table=display&wr_id=408994

I hope google smart enough.

https://www.youtube.com/watch?v=XFNKyuHoars&feature=emb_title

Re: Q90R HDR highlight clipping

FrankieSomeone — Thu, 30 Jul 2020 20:45:53 GMT

Thank you for writing that post btaiji. Very thorough analysis. It's so stupid that Samsung claims it's not a problem. It is for me!
Here's a picture to illustrate what I think is going on here. I think tonemapping is the culprit. Anyone feel free to correct me if I'm wrong.

I think Samsung's goal is keeping average picture level high (bright image) -- as a film purist, I'd love to have the option to keep APL lower so I can see all the highlight detail.

Re: Q90R HDR highlight clipping

btaiji — Fri, 31 Jul 2020 01:56:05 GMT

I agree with you!

It seems that Samsung is setting a different 'feeling'

that they wants to show the viewers at each local dimming stage.

And not only changing the local dimming mechanism at each stage,

but also changing the tone curve,

and I don't think it's working properly.

The image you uploaded is quite convincing,

where did you capture the graph and curve? Photoshop?

Re: Q90R HDR highlight clipping

FrankieSomeone — Wed, 05 Aug 2020 01:05:43 GMT

Yes it's a mockup I did in photoshop, based on my understanding of how tone mapping works.

It's strange that there aren't many references to this in reviews.
There's a brief mention here:
https://www.rtings.com/tv/reviews/samsung/q90-q90r-qled
in the picture quality/local dimming section
"it tends to dim the edges of bright objects, causing a vignetting effect, and small highlights like stars are crushed"
Again, I don't think this is caused by local dimming, but by the tone curve or something like that which is enabled when standard or high local dimming are selected. It can't be caused by local dimming alone (the actual LEDs in the screen) because the detail is missing from the pixels on the LCD panel. Local dimming simply lowers LED brightness, it doesn't erase detail.

I also noticed that the Standard picture mode handles highlights slightly better, but it crushes shadow detail.
Game Mode preserves all highlight detail and has darker black levels than Low local dimming, but it creates halos and it's only available for external sources.

Re: Q90R HDR highlight clipping

btaiji — Wed, 05 Aug 2020 01:24:00 GMT

I also don't think this is the problem of local dimming itself.

There must be something that applies to the pixel itself when I choose the dimming mode.

I wrote about SDR situation, and now I'm preparing for HDR.

There's something I found out on the way, the low setting also changes the highlight.

While standard or high setting burns the highlight gradient like white, low setting gently rubs the highlight.

Everything can't be perfect, but the low setting is the least annoying,

so I'm going to use the local dimming as low.

Since I set Contrast Enhancer to Low in SDR and High in HDR, I think dynamic range is good too.