Dynamic range performance – ISO invariance

The 1D X Mark III doesn't appear to be ISO invariant; boosting an ISO 100 image by six stops gives noticeably noisier results than shooting at ISO 6400. Why bother testing this? Because it gives us an insight into the sensor's read noise characteristics, which help to define dynamic range. Low levels of read noise means you'd be able to shoot a scene at a lower ISO value and brighten it up in post without introducing a ton of noise in the shadows and, meanwhile, will keep your highlights from clipping to white and being unrecoverable.

You could probably get away with shooting ISO 200 or 400 and brightening later on, potentially saving 4-5 EV of highlight headroom. It's also worth noting that the full Raw files on the 1D X Mark III vary greatly in size during this test, with the most under-exposed images weighing in at about half the size of the brighter ones. It certainly appears as though there may be some noise reduction going on, even at the full Raw level, and some data could be thrown away in very underexposed areas – we'll continue to dig into this as we progress with our review.

Dynamic range performance – exposure latitude

Lifting the deepest shadows (as you might if you'd lowered your exposure to protect the highlights but don't want your shadows completely clipped to black) shows the 1D X Mark III exhibiting far less noise than its predecessor, almost to the extent that, again, it appears as though there could be some noise reduction going on. Still, the 1D X III has much cleaner images next to Nikon's D5 and Sony's a9.

The real-world takeaway is simply that the 1D X III's Raw files are more flexible than its competitors, and will stand up better to high-contrast scenes where you want to get as much information as possible into your output file. The following isn't the highest-contrast scene out there, but having good dynamic range allowed me to easily boost some detail in the shadows of the scene without showing a ton of noise.

We think the EOS-1D X Mark III's new sensor bodes well for future Canon cameras – particularly the EOS R5 – and indeed, we already saw a remarkable jump in performance in the company's APS-C sensors with the EOS M6 Mark II introduced late last year.