How to credit a photo taken by someone else in my publication? How do authors normally address a photo courtesy? 
I have a photo taken by Dr. X, I would like to use it in my paper which is planned to be submitted to an engineering journal. How should I respect the photo credit? 
is it okay to write  this in the figure caption, like:

\caption{blah blah  .... (photo courtesy of Dr. X).}


should I even mention the title Dr?
Credit lines for photographs should be displayed conspicuously with the photo or in a footnote on the same page. In general, it should look something like: "© Ansel Adams 2015" or "© 2015 Ansel Adams". Alternatively, if the photo was given to you for general use, use something like: "photo courtesy of Ansel Adams".

Some guidelines for citing images in various formats are posted here: University of Cincinnati. Near the bottom of that website there is a short section with advice on photo credit lines.