How to use Camera presets list I have been exploring the camera settings in the object data tab and changed the camera by selecting (say) Galaxy S3 in the button marked camera presets. I am supposing that that changes the 'render camera' from its default to the focal length and sensor size of a Galaxy S3. 


If that results in an equivalent focal length of 27mm do I need to do anything with that eg set the View lens in the properties panel to match it? It doesn't look like the latter impacts on the rendered view.
If I change the camera from default to S3 does this mean that if I map an photograph taken with a Galaxy S3 camera, that I have better chance of integrating it with objects I model? 


But what is holding me up right now is


Once I have selected a particular camera in object data I cannot find a way back. I tried selecting Blender from the list of cameras but that retains the focal length of the S3 and maybe other parameters. How do I get back to default?
No, the viewport lens only effects the viewport when you are not in camera mode.
Yes, that's the idea.
Add a new camera to the scene. Shift + A -> Camera. Delete the camera. Now, select your original camera and go to the Object Data tab and change the Camera Data to the new camera's data (which is the default).