Do you mean that the brightness is turned up to full on the Windows login screen? If this is the case then you're right that it's the FastAccess "FaceBright" feature that would do that in order to throw as much light on your face as possible for good recognition. You may simply turn off FaceBright if you don't like it. 

If instead you mean that your screen is at full brightness when you don't expect it to be after login (on your desktop) then it could be something else. Let me know which of these two you mean. 

After login. I can see it does the full brightness thing sometimes, but this doesn't seem related to that. And it's very unpredictable, it has not happened for a few days, but then it will do it many times in a row.

If it's not happening when FaceBright activates, then it's likely due to something else. FaceBright certainly should return the desktop to it's normal brightness after login. 

This message board reduced my post to two words, so I'll write it again trying to avoid the above phrase! I also have an L702X. On about 50% of occasions when FastAccess has maximised the brightness during login, the brightness remains at maximum.

I believe that I know the answer to this, but just to be clear, does the screen ever remain at full brightness when FaceBright does NOT activate? Try disabling FaceBright and seeing if the problem persists. 

Try upgrading to the most recent FastAccess version (3.1.55 for the "Sensible Vision" version and 3.1.49 for the "Dell" version) and see if it still happens. If it does, would you mind contacting me directly? I'd like to have you run a diagnostic report on your copy of FastAccess. 

Thanks. 

Mine is already the latest Dell version. Happy to contact you directly... how do I do that?

Use any of the publicly available email addresses on the Sensible Vision website. Sorry, but I can't post addresses here on the forum.