Maybe someone can give a quick answer on something unexpected that happened yesterday.
I was looking at photos I had taken on the rear display of my D300, zooming in and out to look closely at different parts of the photos, when all of a sudden instead of the full display of the image I got the display of the reduced image and the histograms. After unsuccessfully trying to figure out how I had done that, I went into the menu and turned off that display. I couldn't figure out how I had activated that without going into the menu. Anyone know how I did that?