Here’s how you can completely disable HDR photos and videos preview in the Photos app for iPhone and iPad.
Stop Your iPhone and iPad Display from Going to Full Brightness Whenever You View a Photo or Video in Photos App by Disabling HDR Previews
If you have an iPhone or iPad with an OLED or Mini LED display, the Photos app will show you the full dynamic range of photos and videos.
Ever noticed how your display suddenly goes into full brightness when viewing certain photos and videos? That’s the HDR effect, or High Dynamic Range.
While it’s a great way to relive your memories, but not a lot of people are huge fans of it. In fact, lots of Instagram users are against the feature in their app, too.
Thankfully, you can turn the feature off in the Photos app. When turned off, your iPhone and iPad will show you photos and videos in standard dynamic range ensuring nothing hurts your eyes in low ambient lighting.
You can always turn the feature on whenever you like, but here’s what you need to do in order to turn it off.
Step 1. Launch the Settings app on your iPhone or iPad.
Step 2. Scroll all the way down and tap on Apps.
Step 3. Find Photos and tap on it to open.
Step 4. Scroll down and find the View Full HDR toggle switch and turn it off.

You can check if the feature has been disabled by going to Photos and opening any photo or video that was shot in HDR. The iPhone and iPad display won’t automatically brighten up from now on.