I received my Canon 5D Mark III a week ago and have been putting it through it's paces. As soon as I opened it up and put the battery in, I was snapping pictures. Before I get to the technical side of things, I must say The Canon 5D Mark III is the most comfortable camera I have ever held! It feels really good in the hands. There's an indentation on the camera body's right hand side where my thumb fits oh so perfectly. So it's safe to say if you wanted to buy a camera based on "in the hand" feel alone, this would be your camera.
My first trip was to the Sleeping Bear Dunes National Lakeshore just several minutes away from my home. Where I snapped this late afternoon image.
The first thing I noticed about my landscape work is that the dynamic range seems higher than the 5D II. I get better graduations in the sky and not as many blown out highlights. These are my initial experiences but the sensor really does produce a beautiful, vibrant, and crisp image. I couldn't be happier with the IQ of the 5D III.
Next the ISO performance. I did some work for a local Boy Scout Camp photographing interiors of bunk houses, dinning halls, and many other storage and community rooms. For the most part I was shooting handheld at ISO 5000 and the images turned out great! The images were clear and crisp with very minimal noise. A quick edit in Lightroom and the noise was gone. I believe Canon is correct in saying that the 5D III has a full 2 stops better low light performance than the 5D II. I was truly amazed.
I will be running more tests in the near future, this post is just my initial thoughts. In the meantime I am going to micro adjust my lenses and wait for my L plate from Really Right Stuff to show up so I can take some long exposures and star images. I will keep you posted on my findings.