Dark Theme is included in all the system apps for Android Q. But now, even non Android Q users are getting Dark Theme on Google Photos.
Just like other Google apps, the dark mode rather has a dark grey background than full black. This adds more contrast and your photos will now pop-up. The look is thoroughly applied throughout Google Photos. This include the navigation drawer and share sheet.
However, there’s no dark mode support for Google Lens. The dark mode update is rolling out as a server side one. While several users have the new look, it’s not widely available to everyone.
If you haven’t got the update yet, don’t worry as the update will roll out in stages.