Please note: The following review of the Canon 5D Mark III is written from the perspective of a bird photographer. As a bird photographer, more often than not we photograph birds from a set distance and cannot move closer to the subject. The rules are different in this scenario and the test results found here are based on this particular form of photography. Onwards...
Before the 5D Mark III came on to the scene, I had the 5D Mark II but I didn't like it for bird photography for a couple of reasons: auto-focus and fps (frames-per-second). Sure I was able to capture some stunning images, but there were plenty of missed opportunities due to the slow and sometimes inaccurate AI focus while attempting to image a BIF (Bird-In-Flight). Also the 3.9 fps was a bit slow. Occasionally I would miss the moment when an eagle was about to grab a fish out of the water or I would miss the full extension of a duck's wing-beat.
I can't tell you how many times I would say "Give me a 5D Mark II with better auto-focus and faster fps, and I'll show you a near perfect camera for birds—especially BIF."
So in the Spring of 2012, Canon announced the (22 MP) 5D Mark III that was basically a 5D Mark II with better auto-focus and a wee bit faster 6 fps. Image quality was also slightly improved over the already excellent 5D Mark II. What was someone not to like for bird photography?
Well, really not too much but the 5D Mark III became overshadowed by Nikon's release of the D800 with an incredible 36MP full-frame sensor that despite its higher pixel density had very good image quality even at high ISO's. Although I have never used this camera, the images that I have seen come from it are very impressive. Nikon also introduced the camera at $500 less than the Canon 5D Mark III. For bird photography there are two downsides that I can see with this camera: 4 fps and the massive file size means upgrading computers and hard drives to process the images effectively. Neither one of those are show stoppers however and if I owned a bunch of Nikon glass, I would have bought one in a heartbeat.
Back to the 5D Mark III...
I was one of the early adopters of this camera and I have been enjoying the camera immensely. The auto-focus on this camera is superb and it makes photographing BIF a pleasure. 6fps is not too shabby either. I'd prefer 8 or more, but 6 does quite well for most situations.
One aspect of this camera that I just love is that it is a full-frame sensor. Full-frame sensors allow the photographer to do extensive cropping and still come away with enough resolution to show great feather detail. (That's why the D800 is so enticing being a full-frame camera at 36MP.) In my opinion, there is a substantial advantage to photographing a BIF with a full-frame sensor compared to a cropped sensor. Why? I don't have to worry as much about clipping a wing of a bird out-of-frame when compared to a 1.3x cropped sensor (1D Mark IV) or more so with a 1.6x cropped sensor (7D, 60D, Rebel t4i, etc...).
Besides bird photography, the 5D Mark III is an excellent choice for landscape, portrait and just about any other form of photography you can throw at it. For anyone interested in astrophotography or night time-lapse (using an external intervalometer), it's low-noise high ISO features are about as good as it gets. (The Canon 1DX is slightly better, but not by much.)
Okay, that's the good news...how about the not-so-good news? I have a few minor bugs about this camera:
(1) Canon's officially sells this camera for $3,500. I feel it should be priced between $2,500 and $3,000. (This price can now be had through Ebay if you play your cards right.) Canon has a lot of competition out there and they are definitely losing sales to Nikon's D800 which is more aggressively priced and offers more features. This has nothing to do with how the camera operates, but Canon needs to pay attention to this.
(2) Canon's sensor technology is becoming outdated. The 5D Mark III's sensor is excellent but not outstanding. Minor advancements have been made over the 5D Mark II, but I found the improvements to be underwhelming. There has been great progress made by other sensor manufacturers when it comes to dynamic range and Canon needs to advance in this area.
(3) The resolution of the Canon 5D Mark III at 22 MP is certainly acceptable, but I would have loved to see this camera up at 26 to 32 MP. That is where I feel the "sweet spot" is in a 35mm full-frame sensor's pixel density. In that range, the resolution is great for feather detail and yet noise levels are still quite manageable. Nikon's D800 36 MP full-frame camera has done a fantastic job keeping noise levels to a minimum for that dense of a sensor. (I'm sure Canon has something in the works to compete with Nikon's D800. Here's to 2013!)
Versus the 7D -- Image Resolution
Out of all the DSLR's that Canon sells, I have always loved the 7D for bird photography. Although other photographers complain about it's noise levels,I feel this camera has the biggest bang for the buck. Resolution from the camera's 18 MP, 1.6x crop sensor cannot be beat by any of its past or current siblings; including the 5D Mark III , 1DX and 1D Mark IV. Exposing images correctly with the 7D produces stunning detail and the noise can be managed.
As mentioned above, the 5D Mark III has a full-frame sensor with 22 MP. The 7D only has 18 MP but it is a 1.6x cropped sensor. If we were to make the 7D's cropped sensor into a full-frame sensor it would have 46 MP! (Here's how to calculate the size: 18MP x 1.6 x 1.6 = 46MP)
So what does this mean? It means that the 7D has greater pixel density compared to the 5D Mark III. Higher density sensors can usually pull out more detail in a subject, but you pay the price with higher noise levels. There's no such thing as a free lunch!
For this comparison, I did as I always do. I took identical images from identical distances. The sample below compares images taken of a Blue Jay. Images were shot in camera raw and processed in Adobe Photoshop CS6. I used the Canon 600mm f/4 lens using an aperture of f/11 with a shutter speed of 1/400 sec. (I used f/11 due to the close proximity of the bird to the lens in order to get the entire bird in focus.)
Here's a view of the uncropped image taken with the 7D:
Here's an uncropped view taken with the 5DM3:
As you can see from the above images, the 7D's cropped sensor has "precropped" the blue jay, making it appear larger in the frame.
Below: In post processing, I took both images and cropped them identically. No noise reduction, no sharpening was applied to either image.
As you can see in the above comparison the results are not too different, but the 5D Mark III's image is slightly softer. The difference is more noticeable on a high resolution monitor when viewing at 100%, but now we are in pixel peeping territory and frankly, the differences are not enough to sneeze at.
Some of this is due to the lower pixel density of the 5DMark III's sensor, but I also feel Canon put a rather heavy-duty anti-aliasing filter over the sensor for the prevention of moiré. (Moiré is the rainbow effect that occurs with when fine lines are very close to each other. This shows up most often in video, but also in photography as well. It's a pain to get rid of and most camera manufacturer's put a filter over the digital sensor to prevent this from occurring.)
Versus 7D -- Auto-focus
Earlier this year I took both the Canon EOS 7D and 5D MarkIII to a heron rookery and shot extensively with both cameras comparing their ability to track birds-in-flight. As in most instances, I was using my Canon 600mm f/4 IS II lens.
It took a few weeks to find what I felt were the best settings for the 5D Mark III's AI auto-focus. There are so many different settings that it can be quite confusing. But, that is what makes this camera's auto-focus system so good. It can be used in many different scenarios and no matter if you are a sports, landscape, portrait or wildlife photographer, there's a setting that's right for you!
Comparing it to the 7D's auto-focus, the 5D Mark III's auto-focus is a bit snappier in acquiring focus. In other words, the time that the lens hunts to achieve auto-focus is faster—not a lot faster, but it is noticeable. I don't find this in anyway a show-stopper. The difference is small enough that it's hardly worth noting.
As far acquiring focus against a busy background with little contrast between the bird and background, both cameras can give you fits but with the 5D Mark III it is more an issue of making sure you have the center auto-focus point centered on the bird. Because your field-of-view is much larger than on the 7D, the bird appears smaller in the viewfinder and it takes a bit more practice to make sure the bird is in the center of the frame before hitting the focus button.
Here's an example below of two Mallard ducks in flight. As you can see, they take up very little of the camera's field-of-view and it can be tough acquiring focus as these birds fly fast and erratically:
Here's how they look cropped:
The bottom line is if you can put the bird on a focus point, it will obtain focus! Kudos to Canon on an excellent auto-focus. system.
From a bird photographer's point of view, Canon has done an excellent job with this camera. Sure there's room for improvement, especially when it comes to resolution and dynamic range but this camera does a fine job taking bird images.
If I could only have one Canon camera, the Canon EOS 5D Mark III would be my camera of choice. This camera is like the Swiss Army Knife. It can do just about everything with this one camera. The only exception would be if you need more than 6 fps. In that case, the professional Canon EOS 1DX would be my choice. Why not the 7D? I don't consider the 7D to be the best choice for a camera that does about everything. Sports and wildlife are fine with the 7D, but for portraits, landscape and weddings, the 5D Mark III and 1DX would be the best options.
Now, if I were on a limited budget and wanted to do primarily bird photography, I would still give my vote to the Canon 7D. I do believe that in 2013 Canon will finally replace the 7D with a new camera. More than likely, I expect it to have the auto-focus system found in the 5D Mark III. I am also hoping that Canon will keep the resolution high on this camera, but produce lower noise, greater dynamic range and 10 fps wouldn't hurt either.
That's about it for now. I do have more reviews to do. My next review will be regarding video and how the Canon cameras perform doing video work with birds.