Configure Display Resolution in Raspberry Pi

Raspberry Pi 2 supports its HDMI display for 1080p resolution. But, when you want a smaller resolution whether it is in a large display panel, you can configure it manually from terminal.

1) Get the lists of supported resolutions and modes of your monitor

tvservice -d edid
edidparser edid

2) Edit the configuration file

nano /boot/config.txt

3) Find configuration for HDMI group and HDMI mode. The mode is the code shown in the result of first step. DMT group is 2 and CEA group is 1.

For example,

hdmi_group=2 #(DMT)
hdmi_mode=85 #(code 85)

4) Restart your Raspberri Pi

More References: http://www.cpmspectrepi.webspace.virginmedia.com/raspberry_pi/MoinMoinExport/OptimisedDisplaySettings.html