I am developing an application that will use the NTSC output. It displays mostly numeric data (preferably in various font sizes and colors) and a couple of graphic analog-style "meters". The desire is to get the display to be easily readable on an NTSC display (7"). Unfortunately, this is a hard requirement, so I have to use a 7" NTSC Monitor. However, the 7" display is difficult to navigate and even more difficult to read when driving the OS and code editors, so an HDMI monitor is preferred while I am writing code. I'd like to be able to quickly switch between HDMI and NTSC to see how the application looks on the NTSC monitor.
at the terminal you can change display.
tvservice -c NTSC 4:3
should set into NTSC mode 4:3 aspect ratio.
You can switch the other way see http://www.raspberrypi.org/forums/viewtopic.php?f=91&t=5851
tvservice will show options