its a great filter. i am using the gt one. its basically pretty darn accurate no matter the time of year, or time of day. in the game no one setting combination is going to be ideal all the time. but with this you can get it down easy to a couple of adjustments.
maybe its 60% brightness for a morning, or at laguna seca you want it bright so 100% and 100% contrast. great versatile filter. will be a mainstay now.
contrast may only ever be 1 off - 99-101 depending on car dashboard and usually it does not even need adjusting to stay perfect across a wide range of dates, times, and vehicle/tracks.
may be with brightness you could get away with leaving it on 85 and not 100 or some such, but you can take it down to 60 at points, or a bright day in the desert may be you make it 110. did I mention how I like how versatile it is. Its not the best thing to read but it does make a lot of other filters redundant.