iMac clipping highlight information after 13/16 brightness bars (highlight info above 100 luma)

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Level 1

10 points

iMac clipping highlight information after 13/16 brightness bars (highlight info above 100 luma)

I am hoping someone knows whats going on:

When i view this footage on my iMac 2020 at FULL brightness, the highlights in the section of sky that are above 100 luma between the two orange arrows clips. if i lower the global exposure down to below 100 luma, quite a bit of detail in that section of the sky is recovered.

BUT if i lower the brightness on the imac to 13/16 brightness bars i can see those same exact details as if i had not lowered the global exposure below 100 luma. i can see all the highlight info above 100 luma. to make things more confusing - on my LG external monitor, and my m1 macbook pro 13'' I cannot see those details above 100 luma regardless of brightness/contrast settings.

Im mostly wondering what feature this imac 2020 panel has, that the LG and macbook pro 13'' dont have that allow it to read detail above 100 luma.

As well as why the imac is clipping highlight information in the last 3 bars of brightness.

also working noting that highlights above 100 luma is clipped in screen shots, screen records, and after export. is there anyway to retain that detail? at least after export?

iMac 27″, macOS 12.0

Posted on Nov 12, 2021 8:28 PM

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Answer 1

den.thed

Level 10

83,146 points

Nov 13, 2021 8:29 AM in response to Tymbo

Keep in mind that the iMac's back-lighting may be stronger that the LG connected to the MacBook Pro's and that might be the difference that you are experiencing.

The iMac's detail or lack of detail can also come from the Contrast settings. Go to the iMac's System Preferences > Accessibility > Display and make sure that Contrast is set to Normal.

If the contrast was set to Normal. Then I also might try changing the iMac's Display Color Profile: to a slightly darker color profile.

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Answer 2

ku4hx

Level 7

23,604 points

Nov 13, 2021 12:28 AM in response to Tymbo

What app are you using? We have two 2020 iMacs running Monterey 12.0.1 and neither of us have ever seen this.

My experience is not all screens are identical, some will "washout" more than others especially at full brightness.

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Answer 3

Tymbo Author

Level 1

10 points

Nov 13, 2021 7:40 AM in response to ku4hx

its Final Cut Pro.

so just to confirm. On your iMacs, when you are looking at color scopes and the luma wave form, and you are looking at details over 100 luma, you are able to see all those details in the highlights regardless of brightness settings?

do you have any other Mac products by chance?

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Answer 4

Tymbo Author

Level 1

10 points

Nov 13, 2021 9:40 AM in response to den.thed

Thank you for the reply. unfortunately none of these helped. it was already set to normal, and all the color profiles would be darker, but those details in the highlights above 100 luma would still be blown out.

and just to confirm some details: i have the LG connected to my imac actually. so i am comparing how the image looks on the native imac screen, the native macbook pro screen and then the LG.

i can just keep down the brightness i dont mind but i just really want to know what the imac panel has that at least the macbook pro doesnt have. they both have 500 nits, wide p3 color gamut. resolution shouldn't effect highlight detail.... the only thing i can see is the imac supports "1 billion colors" so 8bit+FRC, while macbook only million colors, so 8 bit. but the LG (LGUD59P) is also 8bit+FRC, but that should only really smoothing out gradients not giving me more detail in highlights. the only thing i can think of is some HDR spec, but it isnt HDR content, just shot on Sony A7S III no picture profile, and the macbook and imac should have similar "HDR" capabilities regardless. The LG is also connected with display port 1.2 (or at least i am pretty sure it is - usb-c to displayport from imac), which doesnt support HDR but once again it isnt HDR content so it shouldn't effect anything.

the reason im concerned is because i am trying to purchase a monitor for my new macbook pro MAX, and trying to find a panel that is atleast close to the imac's spec. so id just really like to know what spec this imac has that is allowing it to see detail above 100 luma.

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