Canon 5D Mark IV High ISO NR
Canon 5D Mark IV High ISO Noise Reduction
The Canon 5D Mark IV's four High ISO Noise Reduction settings ("High, "Standard", "Low" and "Off") provide good flexibility in choosing how you want to make the trade-off between subject detail and noise levels. The camera also offers a Multi Shot Noise Reduction option which takes 4 shots, and then aligns and merges them into one JPEG image to average out noise.
See for yourself how the Canon 5D IV's "Standard" and "Off" High ISO NR settings compare to RAW without noise reduction under daylight-balanced lighting. (Note that these RAW images also have no sharpening applied, so they are softer than camera JPEGs at low ISOs.) Click on any of the crops below to see the corresponding full-sized image. Since the Canon 5D IV user manual states noise reduction is applied at all ISOs, we've included crops from the base ISO on up.
The Canon 5D Mark IV's default "Standard" High ISO NR setting provides a decent tradeoff between noise and detail, but it is a little heavy-handed, and struggles to maintain low contrast detail in our red-leaf fabric even at moderate ISOs (as many cameras do). We'd probably shoot with lower settings at higher ISOs and reduce noise ourselves with post-processing (or just shoot RAW). Also note how the "Off" setting doesn't disable noise reduction entirely even at low ISOs as is usually the case, though it appears to do a good job at suppressing chroma noise.