On samsung RV720 notebook, after suspend, the screen is really dark/grey, but visible.
I can correct the gamma using command line or a cairo applet, but the brightness is not responding.
Changed different Linux Os, tried many googled suggestions, none worked for me.
Sounds like your backlight is getting turned down and not restored. Are you able to control the backlight with linux? You might need to pass in acpi_backlight=vendor on the kernel cmdline.
Can you attach your dmesg?
Incredible I tried this solution (between many) months ago, without success.
Now probably with different Linux/Kernel/DE a simple acpi_backlight=vendor solved the problem.
(From Fedora forum I have found out you use Fedora.)
Please fill a bugreport in RedHat bugilla against kernel component, at attention of Hans de Goede.
It is very similar to https://bugzilla.redhat.com/show_bug.cgi?id=861573