When Can XZ Premium Use Full 4K Resolution?

[RoboticBot]

When Can Xperia XZ Premium Use Full 4K Screeen Resolution - To Display Photos / Gallery?

Some advanced reviews of the new Xperia XZ Premium (5.5 inch 4K screeen) state that it will only use the 4K resolution when playing 4K videos in YouTube.  Also, that it reverts to regular Full HD to show photos and all other videos.
I really need a phone that can display the full 4K resolution for photos I place in the gallery, or photo app slide show, etc..  And if I can use the full HDR brightness and tonal range, that would be best.
Will the XZ Premium have apps that I can use to display photos at the full 4K resolution, or will it be limited to YouTube and Netflix 4K videos only?
I understand that I may need to upload photos in a certain format or size in order to have the phone display in full 4K, and that is no problem.  But is there a way to upload my photos to the phone and have them display in full 4K?  And if they have a wide tonal range, would these still pictures use the full range (the HDR range) of the display?  Or can they be rewritten to do so and then uploaded, as jpgs or whatever format allows it?
PS: Would it speed up operation to size each picture to the exact size of the XZ Premium's 4K resolution (I would size to 2,160 x 3,840 pixels if it helps).
Thanks!

[RoboticBot]

Some advanced reviews of the new Xperia XZ Premium (5.5 inch 4K screeen) state that it will only use the 4K resolution when playing 4K videos in YouTube.  Also, that it reverts to regular Full HD to show photos and all other videos.
I really need a phone that can display the full 4K resolution for photos I place in the gallery, or photo app slide show, etc..  And if I can use the full HDR brightness and tonal range, that would be best.
Will the XZ Premium have apps that I can use to display photos at the full 4K resolution, or will it be limited to YouTube and Netflix 4K videos only?
I understand that I may need to upload photos in a certain format or size in order to have the phone display in full 4K, and that is no problem.  But is there a way to upload my photos to the phone and have them display in full 4K?  And if they have a wide tonal range, would these still pictures use the full range (the HDR range) of the display?  Or can they be rewritten to do so and then uploaded, as jpgs or whatever format allows it?
PS: Would it speed up operation to size each picture to the exact size of the XZ Premium's 4K resolution (I would size to 2,160 x 3,840 pixels if it helps).
Thanks!

[Lord_viridis]

Exactly this, it takes a few seconds to render the full 4k displayed image

[Justluk]

Hi @Bjorn_O

I've open a new thread about the 4k resolution in YouTube and as you can read here

HTTPS://talk.sonymobile.com/T5/Xperia-XZ-Premium/How-to-see-4K-video-in-YouTube-Sony-Xperia-xz-Premi...

The display doesn't switch to 4K when 4K quality is selected in the YouTube app neither in the Google Chrome mobile version that use flash player.

I see you are a developer team member so can you please answer to my question here or in my new thread or even PM me.

Thank you

[Sp12er]

I'm curious about that as well, I'm starting to wonder because whenever I try veryfying the screen resolution using Antutu, it always shows 1080 screen even when Im playing 4K video on YouTube thatvs being put on half screen.

And also, I don't notice a change even when I toggle the 4K res when I'm using it to watch a vr video. Now that's weird, that's where the difference should be most stark.

How do I make sure the screen is actually running 4K when it's supposed to?

I can't get antutu to show intentification result as 4K no matter what I do. 

[Sp12er]

Also, every online display resolution checker always show result of 753 x 424 lol

Why is that?