So, I was able to borrow the 5DIV. I didn't get to shoot it as much as I would like (too busy with work), but I did get to try it in a couple of different situations comparing it to the 5DIII. As for first impressions:
  • The Low Light AF is significantly enhanced. I thought AF sensitivity down to EV -3 on the 5DIV vs EV -2 on the 5DIII would not be that big of a deal. But it is. I was able to AF is much lower light than 1 stop comparing the two side by side with the same lens. I have sharp pictures taken in the near dark. Not that I want to take many pictures in the near dark, there are a couple of rooms of different family members dimly lit enough where AF with the 5DIII has been a problem. But I have several shots with the 5DIV where the 5DIII never locked AF.
  • White balance. This is subtle, yet I am finding it to be a bit profound. I would not have said I had an issue with the 5DIII auto WB, but in comparing side by side shots with the 5DIV, I like the 5DIV's better. Felt more accurate and more real. I just finished processing a shot and it took me 5 tries to get the 5DIII's image to where I think it matches the 5DIV's.
  • Weight. I was surprised by how much you could feel the 150g weight difference.
  • Resolution. As expected, more resolution allows for better cropping. Perhaps a bit more perceived sharpness.
  • AF speed. This is the one I was most excited about. I wanted to set up a formal test but ran out of time. But generally the 5DIV might be a little faster, but not much. I was hoping to catch my pug running around, but at least in low light, the 5DIV was not keeping up.
  • Shutter/mirror noise. The 5DIV is much quieter, also it sounds much more like the machine the new mirror mechanism is compared to the slap of the older spring. But I enjoyed the sound.
  • I've heard about battery life issues, but I didn't see it. I had run ~700 pictures (lots of the pug running around) and, I forget the exactly where it was, but I remember not thinking the battery drain wasn't that big of an issue. Maybe 40-50% remaining after 700 pics as well as a good amount of time looking at the LCD and a few videos.
  • Overall IQ (afterall, that is the point, right). I need to compare the images a bit more, but I very much like the IQ from my 5DIII and very much like the IQ from the 5DIV. So far, the more accurate WB is the IQ aspect where I have seen a couple of instances of the 5DIV bettering the 5DIII. But the 5DIII is no slouch in that department.


I did run some noise tests and will be looking at those in more detail. And I will finish processing my side by side images.