The real difference is how the noise behaves when you make exposure adjustments and how that effects the dynamic range of the image. This new generation of sensors allow the exposure of raw files to be brighter +3, +4 or even +5 stops while keeping the noise at acceptable levels. Now there is more incentive to underexpose photos shot in high contrast scenes and recover those details in post, effectively increasing the dynamic range. That's the kind of quality you can see in a photo at any size.
The bump to 30mp makes sense to keep Canon competitive, but personally I think the sweet spot for file size vs. resolution is around 25mp. I’m still glad Canon supports smaller raw sizes for shooting events, this has been one of my big complaints with the Sony.
Some of my favourite new features have been seen on so many other cameras that they may seem boring, but they make a huge difference to me. Built in wifi is something I use constantly with the a7RII and G7X to transfer photos to my phone, and sometimes would use those cameras entirely because of their wifi.
GPS doesn't have a real practical use, but it really scratches an obsessive itch I have give my images accurate metadata. I used to use iPhone apps to track my GPS, then sync it up later in Lightroom, but this is so much easier.
The new Auto ISO does some basic math to set a fast enough shutter speed based on your focal length. Bad shutter decisions by the camera have always kept me from using Auto ISO, but this looks like it could finally be a feature I use.
Adding USB 3.0 sounds pretty boring, but this might be a huge improvement for anyone shooting tethered. I've never been able tolerate how much it slows down shooting, so maybe this means it will finally be fast enough.
A step back is that the battery life has been slightly reduced in normal shoot circumstances, and noticeability reduced if you’re heavily using wifi and GPS. I haven’t run real tests on this so take it with a grain of salt. Canon say it’s a 5% drop when shooting through the viewfinder, but 50% better when using live view.
The touchscreen seemed like it might just be a gimmick, but after only one day of using it I was trying to touch all my other camera screens. it’s a faster way for menu changes and gives strangely satisfying feeling to hit play in videos.
I’m hesitant to count the lack of a fold out LCD screen against them, because the 5D screen as it is just feels right, but it is clearly the way of the future. Being able to shoot comfortably at waist height is something that can be useful every day and I hope they make that change next time.
The updated LCD looks amazing though. When I first turned the camera on I had a memory card from my Mark III inside, and it made those photos pop like they never did on the old camera.
Dual pixel raw still does seem like a gimmick, and after seeing everyone else’s tests I have been too disinterested to even try it. I have no doubt that multi-lens image adjustments with become an important part of photography in the near future, but Canon is still only darling with it at this point.
One subtle refinements I love is the new shutter sound. Canon has improved the motor control on their mirror and shutter mechanisms and when I first heard it I had to double check that I wasn’t on silent mode.
The a7RII first got my attention with it's promise of perfect focus accuracy. The problem with DSLRs like the 5D Mark III is that the autofocus sensor and image sensor are in different places, so the slightest misalignment between camera and lens causes shallow depth of field photos to be soft. In my old 5D, even with micro adjustments, this happened often enough that I gave up shooting below f/2.8 in most circumstances.
Sony solved this problem by measuring the focus on the image sensor, so there is no risk of misalignment. The 5D Mark IV now has the same ability with their new dual sensor focus in live view, and it is impressive. It focuses quickly and accurately even in low light and the touch screen is a great way to set your focus point. I instantly found it useful when I need to shoot over my head and could use the touch shutter to reliably get photos in focus I never could before. It’s a strange omission that you can’t set a focus point to shoot the way you normally would, you are almost forced to use the touch screen.
The live view accuracy is great, but the improvements to the standard autofocus system are much more important to me. One of the first shoots was at night for my wife’s blog AniaB.net, and even in the darkest conditions it was a clear improvement over the Mark III. I’ll need to spend a lot more time with it to find out if I can trust it a f/1.4 but so far it is a clear step forward.
The Canon 5D is a mature camera series that does not need to be reinvented with every update, and the 5D Mark IV keeps pace with the industry. Great dynamic range, improved focus, faster frames per second, and many little updates mean this camera has it where it counts. Sony is still nipping at their heels though, so with cameras like the A99II this may be the last generation of 5D that can be seen as an obvious choice for working professionals. Based on its headline features a lot of people won’t see this as an exciting camera, but to me it is an huge update to my most reliable tool.