The Nvidia Shield seems to only cast the photos at HD res, unlike the Chromecast Ultra.
The Nvidia Shield seems to only cast the photos at HD res, unlike the Chromecast Ultra.
Make sure that both your Shield and the Google Cast Reciever app from the Play Store are updated, I don't see why 4K casting wouldn't work if it works from other apps.
Did you make sure that Google photos didn't resize or change the quality as it does this to save space in the cloud make sure the file you are casting was set to original quality