Hi RJWV90
welcome to this Apple (user-to-user) Community!
Re: "Accessibility issues for visually impaired users on iOS 26"
"We changed the Contrast and Transparency and it still isn’t enough to help".
Good to know your father has you, and your help with his iPhone.
It is not easy to guess which other settings may best suit your father, and his particular vision impairment.
Wondering if Apple Support's online article (link below) can help you customize further:
Read or listen to text in apps with Accessibility Reader on iPhone - Apple Support
The Accessibility / Vision section of the iPhone User Guide - Apple Support for iOS 26 also has articles with tips.
Messaging back and forth is not always the most direct way to solve issues:
More help If needed: You may want to reach out to Apple's Accessibility support team:
How to contact Apple for help with accessibility features - Apple Support
If you wish:
You can send feedback to reach those who work on the accessibility software behind-the-scenes at Apple.
Although it won't help immediately, and they will likely not reply, all feedback is carefully read and logged,
and if others have similar issues, we may see an update that addresses them,.
To provide feedback about an accessibility feature on an Apple product, email the Accessibility team:
accessibility@apple.com.
All the best :-)