Are you using a program to view photos? Going directly to photos on the computer and viewing?
How are you opening them and is there any other darkening issues on this computer?
Please run these steps, look at photos and answer questions above to continue.
Shut down your Mac.
Locate the following keys on the keyboard: Command (⌘), Option, P, and R.
Turn on your Mac.
Press and hold the Command-Option-P-R keys immediately after you hear the startup sound.
Hold these keys until the computer restarts and you hear the startup sound for a second time.
Release the keys.
restart the MacBook and hold down Cmd-R to enter Recovery mode.
Once there, open Disk Utility, selectthe SSD/mac HD drive and run First Aid
Please respond when done.
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credited for the work done with clients. Or, reply to continue if further troubleshooting is necessary.