Layer mask question

Try this Clive...duplicate your top layer (Just to be safe) activate the layer mask and invert it - Ctrl+I.
Apply a levels adjustment and clip it to that layer and adjust to suit. Hope this helps.

Thanks Lillias. Got it. 
I had copied the adjustment layer, but that did not seem to help. So I did what you suggested although I do not understand the purpose of inverting and it was awkward to change levels. However, when I re-inverted the layer i.e., back to normal, then I could adjust the levels okay. I am going to post in in Share Your Work. 
Thank you, 
Clive 
PS: Does it ever seem odd to you that I asked a question here in western Canada and a few minutes later you respond from the UK. Still blows me away. Yesterday, I mentioned to someone (after we got back to the parking lot after our hike) that 30 years ago I worked in Mongolia for one month. In that time, I was able to phone my wife once and sent one fax to her. Here I was half a world away, in a rather remote area, and she had no idea where and how I was. 
 

Thanks. Gosh, I do not know why, but I saw Lillias's comment before your comment. Appreciate your input. 

I got my first computer in 1984 (OMG 39 years!!) but the internet never really got going until mid 90s. Yes, it is so wonderful. In 2009, we spent one month in Chile. I had my laptop on late a night in a sleezy motel (now there is a whole book chapter ) and I get a Skype call from my wife's brother here in Alberta. Sure hits home when you are talking to someone over 10,000 km away! Great stuff. 

Lillias you might regret asking.   This is an abbreviated version ... and way off topic. I am probably going to miss some salient point. 

Well amazingly after 14 years I was able to find the motel because of the photos I had and by using Google Earth. Before we left, a neighbour who often worked in Chile told us it is okay to stay in a hotel but most motels are a not a great idea for tourists. Motels are for locals and our motel was a great example. Oh, it was safe for sure but the purpose of many motels and ours for sure is rather funny.  

Many motels in Chile are used for trysts. The couples might be married but with children at home, couples having an illicit affair or simply unmarried couple perhaps still living with their parents.   

Short version. It is important to say that at no time do motel staff ever see the couple and their car is hidden after entering the walled motel compound. The tryst couple drive into the motel where they have reserved a room by phone. They drive into a walled driveway outside of their room and park by (say) room #3. There is a gate on the walled driveway so the gate is closed thus hiding the vehicle. The couple enter the room from the outside. (The hallway is closed to room guests.) On the wall against the motel hallway there is a (what?) a small revolving door with shelves. (Like a "lazy Susan"...see pink dot in the crude drawing.) The users place the room fee cash on a shelf and when a staff in the hallway come the door is rotated and the money taken by staff in the hallway. If the couple want wine and a meal the goods are placed on a shelf on this revolving door. 

We did enter though the front door to get the room and pay. As I recall we were going to stay at the better place next door but they had no rooms. 

This is a more recent Google Street view of the Casablanca Motel Hotel in Casablanca, Chile, west of Santiago. Based on this top image it appears this is no longer a motel.


Crude schematic 


Google Earth view ... seems there have been changes since we were there in 2009. We stayed in the building on the left. The hotel on the right was more posh.


A photo of the motel sign I took on my birthday on April 8, 2009. It can still be seen in the google Street view although quite broken 


There was a nice winery nearby where we had a lovely meal. (Small photo as the original selfie is not sharp.)