Canon has issued a firmware update for the EOS 5D Mark IV that corrects an issue that some photographers have reported with Bulb mode, plus a number of other minor fixes.
Canon’s firmware version 1.0.4 for the EOS 5D Mark IV fixes an issue in which some photographers have reported a red-coloured area appearing in the bottom-centre of an image when using the camera’s Bulb mode – or sometimes during a long exposure.
Canon firmware version 1.0.4 also corrects a but where the autofocus may not respond when you half-press the shutter button, the AF-ON button or the AE lock button when configured via the camera’s custom control menu.
Canon says the new 5D Mark IV firmware update also improves communication between the camera and SD card.
And for Finnish photographers, version 1.0.4 corrects some wording in the Finnish menu system.
Via Canon Rumors