1- 195.36.03 NVIDIA Driver
Installed without trouble.Seems stable for the time being.
Fn/ UP& DOWN have still no effect on the real screen brightness, although brightness bubble appears and is changed by the Fn/UP& DOWN keys.
Conclusion: no change with this 195.36.03 NVIDIA Driver as regards brightness control.
I would like to mention something I noticed since the beginning (I mean the 9.10 installation with the "official" 185 NVIDIA driver). I do not know if it might have a link with the problem we are trying to solve, but maybe it's worth telling it:
I have 2 ways to control real brightness:
-first one is to use during Grub the Fn/UP or DOWN keys to change brightness, as they work here.
-second is through the NVIDIA Xserver settings window (System-->Preferences-->Display ["Affichage" in french], then going to Xserver Color Correction and using brightness and control cursors, then closing the window with changes.
The strange thing (well, to me..) is that System-->Prefrences-->Display does not open at once the NVIDIA Xserver Settings Window, as I would have expected it to do:
A pop-up window displays (translated): "Your graphic card driver does not seem to manage the extensions needed for using this tool.Do you want instead to use the tool provided by your graphic card pilot supplier?" At the same time a small pink rectangle telling "unknown" appears in the left upper corner of the screen.
But the graphical driver in service is already the NVIDIA one,and knows well that a Seiko 1366 x 768 display is used, so what kind of "switch" needs to be done there?
Nevertheless I answer "Yes" to that silly pop-up window andonly then the NVIDIA Xserver settings window appears, and I can make the brightness /contrast changes.
All this seems to me quite strange, as, if what is mentioned in the pop-up window was really true,(meaning the Xserver settings and/or or graphic driver parameters were not in real use for the actual display) my screen would not be with 1366 x 768 pix.,dispaly as it always is, but the default 600 x 400.
So although the NVIDIA driver is really used, the Xserver settings associated with it are not all used at the same time ? Is this possible?(display resolution is used , but brightness, contrast and so on are not..).
Do you think this is normal and is it the same way with other graphic cards&drivers when you use System/Preferences/Dispaly?I mean ther NOT Nvidia ?Could there be somme link with the unability to control the real brightness through the FN/UP&DOWN keys?
By the way, I made a shortcut using CompizConfig/Commands to open the XServer settings window without going through System/Preferences/Display [ It seems I begin to learn a little bit

2- Fn/F5 not always working at the first strike
I tried the two" vbetool dpms" terminal commands you told me to test.
Same thing happens as with the "samsung-scripts lcd" terminal command: Sometimes it works..and sometimes it does not.The reason is the same: hand is not always given back by the terminal.
So it seems there is an underlying and common reason as the vbetool commands react exactly as the samsung-scripts lcd command do.In my view your lcd script works as it should, but something does not work well elsewhere.
Trying several times the lcd script or the vbetool dpms , I just waited to see if things would sort out by themselves.
In fact, the command (whether it is a samsung-scripts lcd or a vbe dpms ) is indeed always executed!
But:
-either it is executed immediately,
-or it is executed quite later.
In this case "later" is always the same delay: between 29 and 30 seconds ( measured with a chronometer and including at most a one second total error on my side to start and stop the chronometer).
For the FN/F5 command, if the action is not immediate, it also happens after the same 30 s delay (I did not wait that long before, as a second and immediate Fn/F5 strike always give the expected result for backlight if the first strike was not successfull).
I am afraid all this brings more questions than answers, but it is the way my N510 works...I can only report it as it is.