preview rendering and camera control

[fpaolelli]

Hello, everyone!
Again I have a dual problem thanks to the vs tips I realized that I have to make an image of about 1200 x 1300 pixels. the problem is to have a correct visualization of the image to render as I have no references and to the act of rendering the framed field is always greater than the chosen one initially there is a way therefore to understand exactly how the final object will be framed?
second point I have problems in positioning the camera in the sense that when I move this wheel around the focus point and it makes me impossible to place it for example 3/4 compared to the subject.
I hope I've been clear.
Thank you and excuse me!

 

[GP.]

if you select the room opens the preview window, from this you can see in real time the changes made to the view agendo sui grip of the room itself.

 

[lattu]

in these cases I always divide the screen into 2 windows
in the first I look at the floor from above and carry out the various movements of the room
in the second active the shading and look in real time changes.
(the preview of the room is always slightly staggered)