On M(anual) mode lcd reflects the change made to shutter and aperture on the screen visibly. but on Av (aperture) and Tv (Shutter) lcd does not do the same. Is there some setting to enable this feature?
In Tv mode, the lcd will show what shutter speed you have selected. When you press the shutter release button half-way, the camera will focus and will also display what aperture it has selected. Similarly in Av mode, when you press the shutter release half-way the lcd will show what shutter speed the camera has selected.
Nikon D7000 and a bunch of Nikon stuff — oh, and some Canon p&s's too