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Monitoring an HDR Rec. 2020 PQ project.
In Apple’s “Final Cut Pro X: Wide-gamut HDR tips and tricks” document, the first bullet states: “When you color correct HDR images, the highlight details in the wider color gamut or above 100 nits are clipped in the viewer on a Mac display.”
Do I understand correctly that, even though iMac display is above 300nits, the brightness above 100nits is clipped nevertheless?
This same bullet states that:”To play back the wider range of colors in an HDR project accurately, it’s recommended that you use an external reference HDR video monitor.” Does that mean that just because one uses a setting in Preferences indicating a diff attached A/V monitor, the brightness is not clipped?
The other Apple document “Final Cut Pro X: View playback on an external monitor or display” says that: “A/V Output requires compatible third-party video interface hardware and software.”My question is, can one just use Thunderbolt to HTMI connector to monitor on an HDR monitor, or one needs a special device, like those manufactured by Blackmagic design, to connect to external monitor?
James Duke
jduke@lifestorypictures.com -
17 Replies
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The bottom line is that you cannot properly monitor HDR using Apple displays. A high nits display does not mean it is an HDR display. You need the correct AJA or BMD i/o hardware, plus an HDR-enabled calibrated display.
Oliver
Oliver Peters – oliverpeters.com
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Oliver,
Thank you very much for you note. I would like to understand how does the software handle the interfaces. For example, I do have a HDR monitor I can afford – LG OLED 65B7A TV. What I would like to understand is what exactly “correct AJA or BMD i/o hardware” does to shape or provide handshake between iMac Thunderbolt and LG TV? I.e, what does it introduce beyond Thunderbolt-HTMI cable which is not already in the data provided by FCPX?
Thanks.
James.
https://www.lifestorypictures.com -
[James Duke] ” What I would like to understand is what exactly “correct AJA or BMD i/o hardware” does to shape or provide handshake between iMac Thunderbolt and LG TV”
Since I don’t work with these devices, I don’t have an exact, specific answer. However, in order to turn on HDR in the set, metadata has to be passed to it telling the display that the signal is HDR. I believe the newer HDMI specs support that. Therefore, you have to have the correct, AJA or BMD unit (higher end 4K models) that will pass this metadata. The Mac by itself does not. Someone can correct me if I’m wrong on that, but to my knowledge, that’s the current state of things.
– Oliver
Oliver Peters – oliverpeters.com
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Oliver,
This is my understanding exactly. So, I bought the newest Thunderbolt to HTMI cable to connect iMac to LG TV as an external monitor in FCPX.
I do see HDR video on LG TV, however I do not know if FCPX clips the brightness or not. Next, I will try to use HDR test charts to see if it works. I just wish someone would know what exactly is the function of an interface box.Thanks.
James.
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[James Duke] “So, I bought the newest Thunderbolt to HTMI cable to connect iMac to LG TV as an external monitor in FCPX.”
I would be very surprised if that worked. But maybe.
[James Duke] “I do see HDR video on LG TV, however I do not know if FCPX clips the brightness or not”
Which HDR standard are you using and what is the maximum brightness?
– Oliver
Oliver Peters – oliverpeters.com
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This is from Apple’s white paper (page 11):
“Because the viewer shows only the SDR luminance range, it’s essential to use an external HDR reference display for monitoring and grading your HDR footage. Connect this display to your Mac using a Thunderbolt video output device.
Using the video output device manufacturer’s control panel, configure the device to match the settings of your project and reference display. For example, if you’re grading for Rec. 2020 PQ, configure the display and the control panel accordingly.”– Oliver
Oliver Peters – oliverpeters.com
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Oliver,
I am not 100% sure (who is about anything), but I just tested using test video and it seems that A/V output is passing color info Ok, but clips the brightness at 100 nits (same is for the viewer). So, it is entirely possible that the HDR range is passed only through “interface” device. I am waiting to hear from Blackmagic about it. Years ago it was very easy, one could just call Blackmagic tech support and get all the imfo one needs. Today they do not know much and one needs to send an e-mail to the “developer.” I hope I find out soon.
Thanks.
James.
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I forgot to mention, the video brightness is up to 1K nits. LG TV can handle it as a peak. I compress into HDR10, H.265.
James.
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[James Duke] ” but clips the brightness at 100 nits (same is for the viewer). So, it is entirely possible that the HDR range is passed only through “interface” device”
Right. That’s exactly the issue. The Mac’s standard A/V color management isn’t meant for HDR (yet).
– Oliver
Oliver Peters – oliverpeters.com
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