Maximum ISO speed increased to ISO 25600 – Compared to ISO 6400 as optional maximum setting
New 61-point autofocus system with 41 cross-type AF points and five dual cross-type points, High-density Reticular AF, and EOS iTR – none AF points plus six Assist Points on the 5D Mark II. The Mark III's autofocus system was inherited from the then recently announced EOS-1D X, and marks the first time since the EOS-3 film SLR that Canon has put its top-of-the-line autofocus system in a non-1-series body.
New 100% viewfinder coverage that offers 0.71× magnification – compared to 98% viewfinder coverage
Larger 3.2″ LCD with 3:2 aspect ratio. In turn, this means that the native still images of the Mk III completely fill the screen, while the Mk II's native images are displayed with a black border on the bottom of the LCD. Also, while HD video remains letterboxed on the Mk III LCD, as on the Mk II, the 3:2 ratio allows more of the screen to be used for video display.
Headphone-out to monitor audio
Dual card slots: one CompactFlash with full UDMA support, and one SD – the Mark II has only one CF slot.
Along with the 5D Mark II, the shutter life is rated at 150,000 cycles.
Known defects
Canon issued a product advisory indicating that the camera's LCD panel, when illuminated in extremely dark environments, may impact the camera's light metering when shooting. Any camera bodies sold with the issue will be fixed by Canon free of charge, and any body shipped after the first week of May 2012 likely had the defect already rectified.
Firmware updates
Firmware 1.2.1 was released on 30 April 2013 to allow the camera to output uncompressed video via HDMI and permit autofocus ability up to f/8. Firmware 1.2.3 was released on 30 October 2013, fixing a number of minor bugs. Firmware 1.3.3 was released on 29 January 2015, fixing minor menu issues and improved AF control-ability when shooting in Live View mode with a wide-angle lens. Firmware 1.3.4 was released on 14 November 2016, it corrects a phenomenon in which when using the camera with the EF 70-300mm f/4-5.6 IS II USM lens, even if lens aberration correction is set to "Enable", correction will not be applied. Firmware 1.3.5 was released on 29 November 2017, it corrects a phenomenon in which standard exposure may not be obtained, or an irregular exposure may result, when Silent LV shooting with the following TS-E lenses: TS-E 50mm f/2.8L MACRO, TS-E 90mm f/2.8L MACRO, or TS-E 135mm f/4L MACRO. Firmware 1.3.6 was released on 12 September 2019, it corrects a PTP communications vulnerability, and corrects a vulnerability related to firmware update.
