I have a 5s. Same problem. I discovered that the transparency setting seems to relate to the background of the lock screen. If the lockscreen background is white, the passcode screen has less contrast EVEN IF transparency is off. I resolved the issue by taking a photo of a black blanket and using it as the lock screen wallpaper. Now the passcode screen is jet black with bright white numbers. By the way, the phone senses the black screen and displays the day and date as white.
Thanks for following up with that information.
Try restarting your iPhone:
Restart your iPhone, iPad, or iPod touch - Apple Support
If you continue to have this issue, we recommend that you contact Apple Support for additional support.
Cheers!
Hi. Apple Support fixed this:
Settings > General > Accessibility > Increased Contrast: Slide Reduce Transparency OFF.
Fixed immediately.
I understand that the lock screen of your iPhone seems to have very low contrast after updating to iOS 11. I'm happy to provide some help for this.
It is normal for the text on this screen to be white. Based on the image that you've shared, it seems that your Lock screen has a
Change your iPhone wallpaper - Apple Support
Thanks for using the Apple Support Communities. Cheers!
I know how to change wallpaper.
Your suggestion had no effect on problem.
Nearest Genius Bar is over an hour away, so I was hoping to solve this at home.
And there is no Time Machine to back out of the iOS 11 update.
This worked great on my iPhone 6. Thanks for working it out and posting it. The bigger question is why the Passcode/Unlock screen is now so light in the first place. No one at Apple check this out before release ? Things like this that seem so simple but go awry and cost the user some time to overcome after a major update are why the competitor gets more business
having same issue, have tried all of the suggested solutions with no success
This solution worked for me on my iPhone 6s. Thanks!
iOS 11 password screen