When I turn off Dark Appearance Dims Wallpaper it still dims my image.

Hey there, Adam.

Welcome to the Apple Support Communities! Thanks for posting your question about your display dimming at specific times. We'd be glad to see what we can do to help you out with that.

You mentioned that the wallpaper still dims even when the setting to dim when Dark Appearance Dims Wallpaper is turned off. Does your display dim our brighten at any other times? We ask just to see if anything else might be at play here. For example, Auto-Brightness uses the same ambient sensor to make adjustments to the display brightness, so checking to see if that is turned on might provide a little more insight. Double check that in the "About brightness levels" section of Adjust the brightness on your iPhone, iPad, or iPod touch. Also, restarting or updating your iPhone may help as well if there is a waiting software update.

Update your iPhone, iPad, or iPod touch

Let us know what you find out.

Be well.