For Canon 5D Mark II Firmware 2.1.2 Update, please click HERE to download either Windows or Mac version.
What you need:
1. Camera Body
2. A fully charged battery
3. A empty/formatted CF Card (2GB or more)
4. Firmware update file (download from Canon website)
How to update:
1. After you download the firmware from Canon website, double-click on the file to unzipped/self-extract (for Mac); double-click on the file, click OK when a self-extract screen appears (for Windows).
2. Check the size of the firmware update file.
3. Insert a CF card into a card reader
4. Copy or drag the firmware unpdate file to the FIRST window in a CF card via a card reader (if you put it into a subfolder, the camera will not see it).
5. Select <P> mode on camera > Insert the CF card > Turn camera ON > Press MENU button
8. It will appear 2.1.2 version window and then press the SET button. The update will begin. Do make sure you have a fully charged batter, and don't turn off the camera while it's updating. Verifying the firmware version by going to menu as Setp 6.