I have come across two minor bumps with the new Canon 5D Mark IV and my two third party lenses. I am passing the info along in case anyone runs into this. My SIGMA 50mm F/1.4 DG HSM EX when used with the new Canon 5D MK IV with firmware V1.01 produced a JPEG in camera processing with light shaded circles on the image. This is not seen in the RAW. The easy solution is to turn off Peripheral Illumination in the camera settings when using this lens. Problem solved. See image below. The next problem I ran into is My Canon 5D MK IV Live View shuts off immediately after being pressed when using my Tamron SP 70-200 F/2.8 Di Lens produced before May 11th of 2015,. This problem has not happened in video mode, but I have read that touch screen focusing does not work with this lens. The Tamron lens seems to work great in normal shooting mode, fast focus and great images. After some research I found Tamron has several lenses produced before May 11th of 2015 that will need to have their firmware upgraded to fix these issues. Link to Tamron site with info on this issue. I contacted my local camera store, they were unable to update the firmware in the store but will send the lens to Tamron to do the firmware update. They said Tamron has a fast turnaround and it should be about 5 days. I have also read that Canon is working on a Firmware update that will address third party lens compatibility issues. These are minor bumps and has their workarounds. I am still very pleased with the camera so far and no regrets. These issues are not a deal breaker for me. I really like this camera.