Having just received the camera, I took it out of the box and used one of my 7D batteries to get it setup before taking any pictures.   To do so, I accepted the date / time settings, checked the firmware, then attached it to my computer for accurate date & time settings that would be in sync with my other cameras, then methodically went through all of the available settings through EOS Utility software.  Once that was completed, I did the same thing with the camera’s menu system.   Determining your optimal setup will go a lot faster if you take the time to read the manual (you will also understand the limitations and possibilities of the camera much better!)  There are so many variables that you can adjust, and most are straightforward, but some of the naming conventions need more explanation than can fit on a 3” LCD screen.  Others are complex, like the AF Cases, and need detailed explanation and experimentation to figure out what they do.  That being said, Canon has produced an excellent PDF guide to all of the AF menu settings for the EOS 1DX, which is identical in this regard to the 5D.

In an ideal world, I would like to be able to use EOS Utility to set ALL of the camera functions and menus via my computer, not just the few currently allowed.  This would give the distinct advantage of being able to spell out the advantages and differences that each setting makes -- and how they affect other settings -- while you are making them.  As the menus grow more and more complex, this really should be on the table for a camera at this price point.  

Viola!  The camera is ready to use.  Well, actually it is pretty much ready to use out of the box.  But now, it is set up the way that I think I want it.  An hour later, I’m off to a basketball game to test things out.  I’ll be shooting with my trusty old 7D and my brand spankin new 5Diii.  Original plan was to use the 17-40 on the 5 and the 70-200 on the 7D.  That plan quickly changed when I realized just how wide that would render my frame!  So I switched things up and put the 70-200 on my full frame 5D and the 17-40 on my 7D, essentially rendering it a 24-70.  Having used that for a game, I can see why it was so popular with sports shooters on full frame or 1.3 bodies … it really does hit a sweet spot under the basket, and I may just keep using this setup for a while! 

The 70-200 felt comfortable and responsive on the 5D, but it was difficult giving up that little extra reach I have enjoyed with this lens on my 7D.  Due to the layout of the gym that I am shooting in, I am extremely close to the base-line, and doubt that I practically gained much on the wide end, but time will tell. 

Shooting tonight was not my typical night out.  I was testing a new camera and trying a new technique (back button focus) while using a new lighting setup.  Lots of variables, and lots of potential for things to go wrong.  My first impressions:

1. 5D Mark III camera is amazing.  It feels a little heavier than my 7D, but fits my hands well, and feels rock solid.  It operates that way too.  After getting it set up, it just works the way you want a camera to.  Everything is in the right place, and the viewfinder is nice and bright.   I particularly like the new “lock” button on the mode selection dial, and the fact that when I lock the other dials, I can lock both aperture and shutter knobs from being accidentally changed.  Battery life looks like it is going to be good - after 428 shots, it still has a 75% charge.  Some speed junkies will complain that the “motor speeed” is only 6 fps.   Even with sports, this is not a limitation to my style of shooting, since I rarely “machine gun” a target.   I was a little concerned that my max sync speed was reduced to 1/200th, but that is not an issue.  Those coming from a crop body will be impressed by the full frame coverage, and previous 5D owners will be stunned with the very usable AF system.   AF is fast, but does not feel much faster than my 7D with the 70-200.  It is, however far more accurate a greater percentage of the time.  When going through my images later, very few were deleted because they were not in focus.  I do think AF is going to shine when paired with lesser lenses, and may improve once I experiment with the AI Servo cases.  I should, however, be careful in passing judgment on the AF performance since I was also trying Back Button AF for the first time. 
2. Speaking of BBAF, it worked much easier than I had thought.  Previously, I was using the shutter button for AF, metering, and release, and the * button as AF-Stop.  That was working pretty well, but after just one game,  I have been sold on the Back Button AF method.  My only gripe about it is that changing the AF points is not as easy now since my thumb is already occupied.  I also think I will go back to “normal” AF with wide angle lenses.  Back button seems more suited to the long lenses.  (see the Canon Learning Site for more information on BBAF)  My major limitation tonight was not BBAF, but that my grip had not arrived in time for the game.  There is good reason that the 1 series bodies have a vertical grip built in!

As I start looking through my images in Lightroom, I am absolutely stunned.  Shell-shocked.  Flabbergasted.  The list of adjectives could go on.  There is simply no comparison of these images to those that came out of any digital camera I have previously owned.  I knew to expect better subject/background separation because of the full frame body, but I was not expecting the superior file quality in absolutely every respect to be this dramatic.    A love affair is beginning!  Let me count the ways:

1. ISO - I shot at 800 tonight, and there was no perceptible noise.  I could see the smudges on the backboard, but not the usual digital artifacts adding to it.  That means that cropping in tighter will not be a problem …. Except that I usually shoot pretty tight to begin with!
2. Skin tones are beautifully rendered.  I think this is the first time I have had perfectly rendered skin tones right out of the camera.
3. Details are far superior.  Not just because I have more megapixels to record them, but have less noise, moire, CA, and pretty much any other kind of aberrations or artifacts.  This camera makes use of the higher LPM resolution of my “L” glass.
4. Dramatically better Auto White Balance means less tweaking later.
5. Bokeh - not just the circles of light in the out of focus areas, but the way that subjects stand out in front.  They become more three dimensional.

There is great truth in the saying that you should invest in quality glass rather than chasing camera bodies.  The Lens will make or break your image no matter the black box it is attached to.  Quality lenses will be a requirement when using a camera of this quality.  It will show the weaknesses of inferior lenses, and I am glad I have the “L” glass for this camera simply to keep up with its resolving power.  That being said, there does come a point when the camera body itself makes a difference.  Going from a crop body to a full frame body makes a huge difference in your lens performance, especially in the out of focus areas that make a picture pop in just the same way as stepping up from a Kodak Instamatic to a 35mm to a 4x5 camera did in the film days.  It makes a great deal of difference in pixel density and pitch and all kinds of technical ways that I am not qualified to talk about but influence the quality of the output file.  You’ll notice smoother gradations in color changes, better detail  bright whites, less noise in the shadows, and faithful color representation throughout.  In short, you finally will capture what you saw through the lens.   What I can say without reservation is that stepping up this far makes a difference in the pictures that you are able to capture.   

Be forewarned that processing the RAW files from this camera will require a fast computer and lots of hard drive space.  The provided software will yield optimal results in processing, but Lightroom 4 (ACR 7.3) does a pretty good job at rendering them as well.   This camera is for the serious photographer who is willing to invest not just the money to buy it, but also the time to learn to use it properly, and appreciate the results it helps produce even if others cannot see the difference.