These apps offer features a bit more advanced than the stock camera app.
Often there will be a PDF with specific instructions for your camera and firmware included in the compressed file along with the firmware.
Fixes a phenomenon in which the Live View exposure simulation warning indication, in which would normally flash when the image is not being displayed at a suitable brightness level (under the conditions of low brightness and high brightness), does not display properly during Live View shootring. Press the Cross keys, and you will see the "Firmware Ver. Note: Select mode (or one of the other creative modes).
The version of the firmware will not appear in the basic zone. (1-A) Battery Pack LP-E5(The battery pack must be fully charged.) (1-B) AC Adapter Kit ACK-E5 (sold separately) (2) SD card (64MB or more, 2GB or less) In order to supply power to the camera, either (1-A) or (1-B) is necessary.
In most instances a firmware update is provided directly from the manufacturer of the camera.
You can find some talented engineers creating their own firmware to run in another manufacturers hardware.