Current EDR headroom does not increase when lowering iPhone brightness.

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OctoBHVR OP

Created May ’23

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I am using an iPhone 13 Pro. It has an HDR display with potential EDR headroom of 8. I measured the following:

Phone brightness: from 0 to 60% --> EDR Headroom = 8

Phone brightness: from 60 to 100% --> EDR Headroom ranges from 8 to 2.2

Why does currentEDRHeadroom remain constant when decreasing the iPhone screen brightness from 60% to the minimum? Shouldn't both value decrease continuously?

Answered by FrankSchlegel in 752858022

I think this is a design decision from Apple's side. You are not supposed to set the pixel brightness to more than 8x the current brightness of the screen. Otherwise, you could "blind" the user with very bright pixels, even though they set the screen to be dim.

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Answer 1

FrankSchlegel OP

May ’23

Accepted Answer

I think this is a design decision from Apple's side. You are not supposed to set the pixel brightness to more than 8x the current brightness of the screen. Otherwise, you could "blind" the user with very bright pixels, even though they set the screen to be dim.

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Answer 2

OctoBHVR OP

May ’23

Right. I think what this bar chart explanation misses is: for iOS, when brightness is lowered, the peak luminance is also capped to keep headroom concistent.

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