Pls Help Test Z9X with Oppo 203

Fun fact: Mad Max: Fury Road has a maxcll of 10,000 nits and maxdml of 4000 nits, as you described. However, on LG OLEDs, it will STILL use a 10,000 nit tone curve (as it should) since maxcll is 10,000 nits. It takes the LESSER of maxcll/maxDML, unless one of the values goes over a threshold. So in this case, even though maxDML is 4000 nits, it will still use 10,000 nits because the maxcll is over the 4200 nit threshold or whatever the TV uses to decide on the tone curve. Otherwise, if it used a 4000 nit tone tone curve instead, a ton of stuff would be clipped. Just an fyi in case anyone was interested in how LG OLEDs handle maxcll/maxdml when deciding on the tone curve.

Also, what did you mean by dolby vision tone maps after 700 nits? Just curious. How does this work? Does dolby vision use "tone curves" in the same way as HDR10 (1,000/4,000,10,000 nit curves for example) ? I actually don't know.

 

For LG OLED TVs:

DTM On/Off Target maxTML is determined by the HDR Static Metadata as follows:
--If maxDML = maxCLL = 0 (not provided), then Target maxTML = 4000 nits
--If maxDML = 0 & maxCLL > 0, then Target maxTML = maxCLL
--If maxDML >0 & maxCLL = 0, then Target maxTML = maxDML
--If maxDML >0 & maxCLL >= maxDML, then Target maxTML = maxDML
--If maxDML > 4000 nits, then Target maxTML = maxDML
--If maxDML <= 4000 nits & maxCLL < maxDML, then Target maxTML = maxCLL
--If resultant Target maxTML <450 nits, then Target maxTML = 450 nits

So pretty sure if maxcll is larger than maxDML and over 4000 nits, it will use the 10,000. Otherwise you'd have a ton of clipping. It's still a bit confusing and a bit challenging to test easily but I am pretty sure this is how it goes.

 

All this stuff is beyond me lol but can say the 10,000 and 6,000 nits content does look amazing on C9.

 

Well actually don't be fooled. Your C9 only goes to 800-85o nits. So you're not actually seeing content over that luminance value. it's being tone mapped along a curve. Ironically, the higher the tone curve, the dimmer highlights actually get becuase of the severe roll off of a 4000 or 10,000 curve. Now these movies are mastered for those tone curves most likely, so it should hopefully still look good. This avoids major clipping issues on TVs like ours. In games however, which often let you adjust the HDR peak values, using a 10,000 curve will actually dull the living hell out of everything, lol. That's why HGIG is preferred (when it makes sense). That way, highlights are brighter and just hard clip at the maxTML of the panel. Tone curves actually dull highlights. It's a bit confusing and a huge rabbit hole to go down ha.

But basically, a movie with a maxDML/MaxCLL of 850 nits will look nicer (on a C9 - because it's basically HGIG with a peak brightness = maxTML of the TV) than a movie with a maxcll of 10,000 nits and maxdml of 10,000 nits. As stated before, this is because with the 850 tone curve, it's basically doing HGIG and not rolling off at all, whereas on the 10,000 nit curve, it's a exaggerated rolloff.

@Markswift2003 let me know if anything i'm explaining is wrong.

 

Of course, im not expecting to see 10,000 nits on my TV. There's like only a handful of devices like the Sony mastering display that can do that. Still, the colors and brightness look amazing in 10,000 compared to their counterparts with 1000 nits.

 

But like I said, the 1000 nit movie should actually appear brighter since a 1,000 nit curve has a very sharp rolloff near maxTML (850 nits). The 10,000 nit curve has a very exaggerated rolloff. This means on a 1,000 nit curve, 700 nits will probably be around 700 nits. On the 10,000 nit curve, 700 nits source signal will actually display at like 500 nits or something on your TV. Maybe even less. See visual below:


https://imgur.com/a/ZuF1djq


Now like I said, if a movie is mastered at 4000 nits or 10,000 nits or something, then likely it's been adjusted to account for this. Games are a different beast.

But in theory, a movie mastered at 850 nits should follow the PQ curve perfectly (assumign your TV has accurate EOTF tracking which LG's does) and will look better than a movie mastered at 10,000 nits.

 

That's all great but I am just letting you know what I see on the TV. You have to remember that just because a movie is master at 1000 nits, its not displaying 1000 nits at all times but a 10,000 nits movie that has been tinkered with may be displaying 500 nits at all times and then some. I dont know if that's true or not but I've seen some 1000nit movies hit 100 nits in some scenes and that's a shame. Like those Pirate movies or Heat UHD.

 

Yea, sorry, I should have clarified. I'm talking about 1,000 nits and 10,000 nits assuming that MaxCLL = or is close to MaxDML. So yea, if you have a movie mastered at 1,000 nits and it only hits maxcll of 400 nits, THAT will look way dimmer than a movie like mad max where maxcll is like 10,000 nits (since 10,000 will show at 850 nits on your TV since it's using the entire luminance range).

 

Yes, it kind of uses tone curves - Dolby Vision is a PQ based technology (Perceptual Quantiser - a type of gamma curve), but like HDR10+, it's dynamic - ie the tone curve changes depending on scene/frame content and the display capabilities vs maximum luminance.

If the display can do 700 nits then up to that point, no tone mapping is needed - so if MaxCLL is 700 then no tone mapping is required because the display can hit that with no gamma compression (with Dolby Vision and HDR10+ there is other stuff going on as well though...).

Because the maximum nits defined in the Dolby Block (Target Max PQ) is 700 nits in this case, anything over 700 nits needs to be compressed (ie tone mapped) to fit into that 700 nit max. So what happens is the the tone map starts soft clipping the PQ curve before 700 nits so that everything above can be squished in. The higher the maximum luminance is above 700 nits, the more aggressive tone mapping is needed which involves a combination of starting the roll off earlier and being more aggressive with it so that the max Luminance - say 1000 nits, 2000 nits, whatever - is mapped to 700 nits.

So you can see that 0-1000 nits will need much less fiddling with the top end of the gamma curve to fit into 0-700 nits than 0-2000 nits. And it's only the top end of the gamma curve that gets compressed (rolled off) because we're only talking about specular highlights - the overall APL (Average Picture Level) shouldn't be vastly different to the SDR grade.

And of course this is all done dynamically in the case of Dolby Vision, generally on a per scene basis but occasionally per frame.

 

That is very interesting, thank you. So it seems to me like it's basically tone mapping in the same way as HDR10 but the curves change dynamically rather than being static (which makes total sense). Yea on my LG C1 you can test out how different tone curves look in games. If the game allows you to adjust the peak hdr brightness value, you just max it out. You then take that max value and match it in the TV's hdmi signaling override menu. So if the game puts out 2000 nits with the slider maxed out, you select 2000 nits for maxcll/maxdml in the override menu. Then you can see how different curves affect the image. So in my example, a 1000 nit tone curve would clip a ton and a 10,000 nit tone curve would dull the hell out of the highlights.

 

And me too - I feel your frustration lolol. I wish there was an article or something to read up simply enough to understand - @Markswift2003 could earn a small fortune spilling his mind for us and I for one would be willing to pay

 

I've touted this website around quite a lot and it's probably the best description of HDR I've seen - this guy cuts through all the BS about HDR being "brighter" blah blah blah.

Worth a read:

https://www.lightillusion.com/what_is_hdr.html

 

Thank you Mark, not seen it before

 

Thank you! I just bookmarked this and plan to read through it later.

 

Anyway....to get back on topic, do we have any ideas what is going on with the picture quality between the Zidoo and Oppo? lol.

 

@Markswift2003 back off topic again....lol, so I was wrong. For mad max fury road, LG TVs will use MaxDML in this case. So it would be using a 4000 nit tone curve even though maxcll is 10,000 nits. This would mean that anything over 4000 nits is clipped, correct? So was this an oversight with the blu ray? Or is it by design? Is it the "artistic intent" to have a ton of the highlights clipped? I am assuming it's probably just those fire effects that reach 10,000.

 

All I can say is I look forward to the Zidoo of year 2024 when it finally supports FEL metadata and hope that replicates the image of the Oppo then. Until then its a two machine setup for me.

 

I think it's been made abundently clear that FEL does not explain the PQ differences we're seeing here. It's clear something else is going on here. Or did I misunderstand everything?

 

Its the only thing missing in Z9X in comparison to the Oppo so that's what I am landing on. I wish I knew how to read that FEL graph of the movie to say otherwise.

 

Mark tested this on his blu ray player which plays FEL though, and he said PQ was similar, if not the same. Idk though since I don't have an Oppo so I cannot test.