If you can't use the Depth of Field effect mode on your iPhone with iOS 16, here are a few solutions you can try:
Check device compatibility: The Depth of Field effect feature is supported on iPhone XS and later. iPhone X and earlier models may not support this feature.
** Shot with Portrait mode: The Depth of Field effect is best suited for portrait mode shots where the subject is clearly distinguishable from the background**.
Remove the lock screen widget: Widgets on the lock screen may interfere with the depth-of-field effect. Try removing them and see if that fixes the issue.
Make sure the wallpaper is in the right position: The position of the wallpaper may affect the depth-of-field effect. You may need to adjust the scale or reposition of the wallpaper for the effect to take effect.
Use ** in jpg format: Make sure your wallpaper is in JPG format, as the depth-of-field effect of iOS 16 may not support other formats.
Enable the depth-of-field effect in the settings: Go to your iPhone settings, select "Wallpapers", select the lock screen wallpaper, and make sure the depth of field effect is enabled.
Restart your iPhone: Sometimes, simply restarting your iPhone can fix a glitch that prevents the depth-of-field effect from working.
Update iOS: Make sure your iPhone is updated to the latest version of iOS, as updates usually contain fixes for such issues.
Reset all settings: If none of the above methods worked, you can consider resetting all the settings of your iPhone. This will not delete your data, but it will restore the system settings to their default values.
If you've tried all of these steps and still encounter issues, you may want to look for more troubleshooting steps or consider professional support.