The only thing I've seen it do is override my brightness setting to make my screen go to full brightness when I've set it lower.
One is that HDR displays can usually get MUCH brighter. An iPhone 5 could do 500 nits. An iPhone 14 Pro can do 1,000 - 2,000 nits.
That’s what’s used here. You get all the same colors as before, but max brightness is way brighter.
The other thing is color gamut. The standard we had for a long time was 24-bit color, so ~16.7 million colors. Instead of having 8 bits per channel, screens may now have 10 or 12 bits per channel. I can’t find just how many a modern iPhone has.
This means there are more shades between black and 100% bright red. There are more variations between blueish green and greenish blue. Gradients can be smoother. Objects that are mostly one color (yellow corn, a red apple, etc) now have more options the can use to provide definition and details.
In a very dark scene, there are now more dark shades to show things with. When looking at bright clouds, they don’t have to be all white and washed out.
And combined with the increased brightness a scene can show definition in both dark and bright areas without having to wash everything out.
I have one Dell made a few years ago. It supports the additional colors of P3 but isn’t any brighter than any other quality normal display of the time.
But if you do want to "use the full potential of your hardware", there was some third-party app that used private APIs to set the screen brightness above that limit. I don't remember its name.
I imagine very few people, i.e. graphics designers, want true sRGB colours. The rest (i.e. normal people) adjust the brightness to the ambient conditions, adjust their eyes to the current "white" and expect everything to follow suit.
This is not Apple specific, and not what HDR is designed for. No implementation works as you expect. Linux doesn't even support HDR at all. When I plug in my non-Apple HDR monitor into my Linux desktop the brightness remains capped at SDR since there is no hardware support. Even when Linux does eventually support the hardware, it is unlikely that any UI will use HDR by default. The UI would need to be redesigned for HDR specifically. It is way too bright for sustained usage on a UI. Uncomfortably bright to the point where it may cause damage to eyesight with prolonged use. It is intended for dynamic scenes that are occasionally bright in some parts of the image, as in TV and movies. I would never use that as a default global brightness level.
The difference is while most things support sRGB, those other color spaces may just be outside what the display can handle. My Ultrafine 5k for instance does not show a discernible difference between the two QR codes.
You also have the issue that static images displayed at higher brightness will use more power and require quicker mitigations to prevent burn-in, so an 'ultra white' background may just not be something supported for a web page.
If this were true, monitor brightness would be hard-set at 80cd/sqm, which would be borderline unusable during the day and way too bright in the dark. But hey, true sRGB colours!
So if they they just mapped the new brightness everything, everywhere, would look wrong. And people would complain that the iPhone is broken. And they have to redo all their websites/apps. And when they do, they look wrong on every other device.
This is the only sane way. It has to be something people opt-in to. That’s what Apple did.
I will say that it is really annoying to have an HDR video just be way brighter for no reason, and I kind of hate HDR for this and this alone.
[0] This is also why streaming services have shows that are WAY TOO DAMNED DARK. Related: the people mastering the audio have also decided to make all the dialogue way too low because fuck people with hearing disabilities[1].
[1] An audio engineer was asked about this and he outright said he doesn't master for substandard audio setups. No I don't remember the source, it was from one of those articles that show up on the Firefox new tab page. Yes I am kind of reading into things and getting angry about it.
It was Christopher Nolan. He said
"The only platform I’m interested in talking about is theatrical exhibition."
and
"“We made the decision a couple of films ago that we weren’t going to mix films for substandard theaters... We’re mixing for well-aligned, great theaters... At a certain point, you have to decide if you’ve made the best possible version of the film and you’re trying to account for inadequacies in presentation... That’s chasing the tail. It doesn’t work. I will say, with our sound mixes, we spent a lot of time and attention making sure that they work in as predictable a way possible."
https://www.indiewire.com/features/general/christopher-nolan...
https://www.indiewire.com/features/craft/dunkirk-too-loud-ch...
Doesn’t that happen because shows are mastered for 5.1 systems and the dialogs are put in the centre channel, whereas most of us are watching in stereo with poorly setup automatic remixing?
Every (compliant) screen will produce that range, when given numbers between the minimum and maximum. It's nowhere near every color we can see (the dark gray area), but it is a decent manufacturing target and it covers a very practical area of our vision.
Screens could just produce their maximum range all the time... but then you'd get screwed up colors, with every display being different than the others (some redder, some greener, etc.). Hence standard color ranges, like sRGB, so bananas used for color scale always look the same shade of yellow. That triangle looks the same on my screen as it does on yours, assuming the manufacturer cared at all about consistency. (remember the stupidly red OLEDs when they were new? they looked awful, humans looked like oompah loompahs)
So screens are capable of more than they normally display, sometimes by a pretty large margin. Somehow you have to tell the screen to go beyond its normal range, to show yellower yellows for super-bananas - that's HDR.
It does give you more range.
A lot of modern screens literally can't run at their full dynamic range, they would draw too much power and/or get too hot (some professional displays I use at work have a power cable as thick as your thumb and radiate heat like an oven with the door open. They also require following warm-down procedures to prevent the electronics from failing if they cool down too quickly when you power them off).
They can, however, run at full brightness for a small section of the display or brief periods of time. HDR videos are one way to instruct the screen to do that.
(obviously, how much range it can give you depends what screen technology you have - Apple's software has supported this for a long time, but even some current model displays they sell can't really do HDR properly - though many that "cant" to HDR are able to make a best effort using complex software tricks)
It is usually combined with new display technologies that can emit unusually high brightness levels. On a traditional display there is obviously no point.
I can understand the increased granularity, if you're making monitors that go much brighter, then you get more light levels, but why define the old maximum to be less than the new maximum?
You might be interested in reading https://prolost.com/blog/edr which explains in more detail.
Whether the effect is significant depends on a lot of stuff; how the display is built, how the codec works, your viewing conditions, and not least of all, whether the content "looks better" artistically with that much more range.
Just like the compression audio effect clips the range of music and how some pieces of music sound more expressive when the range in amplitudes is used well for artistic effect.
It gives you more range.
> so what does it actually do?
If you have done a little C programming, you will know (or can check) that a 32-bit `int` represents values from -2147483648 to 2147483647 while a 32-bit `float` goes from -340282346638528859811704183484516925440. to 340282346638528859811704183484516925440. - clearly more "range". This is almost exactly what is happening here.
(If you haven't done a little C programming, you should!)
> The only thing I've seen it do is override my brightness setting to make my screen go to full brightness when I've set it lower.
That is too bad. My experience is very good: only the QR code becomes much more striking, while the rest of the display remains the same. Perhaps it is implemented by increasing the brightness on your display to compensate for the reduced range available due to your brightness setting, but if that's what is happening here, something else is also compensating the colours to make the non-HDR areas of my display darker so that I cannot notice.
What’s happening here is using a short (16 bit) rather than a byte (8 bit), although not quite to the same extent, for each channel. HDR allows you to represent 2^6/12/18 times as many colors as SDR.
Basically if srgb content was just naively stretched to rec2020 it'd look garish and oversaturated instead of what the designer/photo/videographer intended. If it was additionally stretched to HDR, it'd look garish and eye-searingly bright.
Because the differences between HDR displays and SDR is so dramatic it is forcing everyone to scramble to do color management as the result would be pretty unusable otherwise.
Look at the second example ( red images) and click the Display P3 option.
Do you see the symbol inside? No? Well then your display / monitor isn’t capable of showing a colour range higher than sRGB.
HDR is similar in respect to brightness and contrast.
If your device supports HDR, then there’s more steps in the brightness scale that your monitor can display.
HDR standards require higher bit depth and define higher peak brightness. In addition, and this is probably technically the toughest bit, they define dynamic metadata formats which define tone mapping as the content changes [0].
One thing you may be missing about the particular effect we see on this website is that it disappears as you turn your device brightness up. So you can still get that brightness with SDR content.
[0]: https://www.avforums.com/articles/what-is-4k-hdr-dynamic-met...
And there is no need to cripple anything. Brightness adjustment can/should let you put SDR white all the way up to the max full-screen brightness. If a manufacturer cripples that it's not HDR's fault.
But it's also important to note that "max full-screen brightness" is often a lot less than maximum spot brightness.