Last week I had the problem that my shot cam was faaaaaaaaar faaaaaaaaaaar away from my character but I didn't want to change my cam position. Therefore I created a small Zoom Tool with which you can zoom into your scene without changing any attributes like Focal Length Position or Rotation. To see how it works and how to install it I have made a small video. If you are more advanced with the scripting stuff just take a look into the .mel file where you will find a small instruction.
The interface gets parented directly under your persp cam, if you are using a different camera to navigate you have to re-parent it. I have added an new attribute after recording the video which you will find when you select the zoom controller called multiply. This attribute multiplies the zoom level and if you want to zoom out for some reason put it to a negative value like -1 but never to 0.
I only tested it on Maya 8.5 and 8.0 I'm not sure if it will work on lower version but I hope so 😉