I asked a few people this and I got different answers.
Currently have a Nikon D80.
If I using a big aperture e.g. f4 and look at the subject (portrait) with a view finder, the background will look blur. If I then switch aperture to f11, will the image in the view finder be different after I press the shutter halfway? or do I need to press the depth of field button to see the increased depth of field?