By now, it is almost safe to say that the Canon 650D, or Rebel T4i, landed in Canon's somewhat congested mid-level DSLR line-up without much of a hoopla, well, the camera managed to garner some attention, but for all the wrong reasons. There was the product advisory on a series of the camera bodies where the rubber grips could turn white and causes skin allergy, and then there is the new Hybrid AF System that failed to impress some of the most reputable reviewers in the industry.
I wrote an entry about the 650D a few months ago when mine was just fresh out of the box; coming from a a long line of compact camera users who first migrated to Sony's Alpha system, I am fully aware of the limitations of the live view auto-focus system used by the major DSLR makers, Canon and Nikon. Sony uses a completely different live view AF system with their SLT line-up, and their non live view, first fullframe A900 is on its way out, to be replaced by the SLT-A99.
I believe it was Nikon that first introduced the Hybrid AF, it was featured in the Nikon 1 series, where phase detection pixels are somehow fabricated into the image sensor itself to increase focusing speed and accuracy while a camera maintains live view throughout.
The 650D's Hybrid AF doesn't quite behave like a "true" PDAF sensor, at least not in the traditional sense. PDAF is able to judge almost instantly where the subject is from your camera's sensor focusing plane, but the Hybrid AF sensor on the 650D, behaves more closely to a DSLR that is performing CDAF than one that is doing PDAF. The Hybrid AF gets confused easily in a scene with many moving objects (imagine a room where a bride is preparing to walk down the aisle with her friends fussing over her with ten thousand pins and enough flower arrangements to make you nauseous), which is something I've come to expect from traditional DSLR CDAF.
Eventhough the 650D focuses more reliably and faster than the 600D and 550D (in live view), and I dare even claim that it focuses faster and as reliably as my work camera, the 5D Mark III (again, in live view), the Hybrid AF sensor failed to impress me, and I found myself using the camera through the view finder all the time simply because I cannot wait 2 to 3 seconds for the camera to lock focus, or worse, give up completely after that. All the extra focusing features that come with the touch screen capabilities, such as "tap to focus" or "tap to release shutter" are seriously impeded by the camera's inability to achieve focus fast enough to make them practical.
To top it off, the Hybrid AF technology have inadvertantly hurt the image quality of Canon's impressive 18 MP sensor. This sensor is found on 7D, 60D, 600D and 550D, and it produces one of the cleanest RAW files I have ever seen, especially at higher sensitivities. The introduction of the Hybrid AF somehow caused the noise level to take a tiny bump in the upward direction, but thankfully, the noise difference is only obvious in studio tests, and is almost impossible to see in real-world use.
The 650D weighs a little bit more than its near identical brother, the 600D, and in a way, it gives the camera a little more heft when you mount those big and heavy L lenses on it. The battery grip BG-E8 definitely helps with the balance (and you can borrow it from your existing 600D or 550D), and the buttons and controls (ISO control especially) have been rearranged and shifted slightly to make the very small camera easier to control without you having to take your eyes off the viewfinder.
The integrated speedlite controller remains somewhat limited, it can control up to two firing groups at once, but not more. The good news is, if you're the kind of photographer who spends alot of time shooting in studios, you'd know there are a hundred things you can easily do to your remote flashes to give your subjects just the right kind of lighting.
One thing I do wish for the 650D is that Canon would raise the Maximum ISO ceiling for the Auto ISO from 6400 to 12,800 or even the top setting availble to the camera, at 25,600. I shoot in B&W and natural lights for weddings, and the grains really dont bother me that much, but having to manually bump the sensitivity to 12,800 and H (25,600) whenever I need that extra shutter speed, that really bothers me.
Eventhough the Hybrid AF did not impress me, the 650D is in my opinion, a great DSLR. It is responsive, thanks to the new Digic 5 processor, and very light when paired with smaller prime lenses, and with the battery grip attached, the camera is bulky yet light enough to allow you to hang onto for hours without feeling like your wrists have left your forearms. The touch screen interface makes everything easy to access, especially when used in combination with the buttons already found on the camera. My colleagues have caught me tapping and swiping the screens of other Canon bodies more than once; I'm amazed at how much my fingers have been spoiled by the convenience of the 650D's capacitive touch screen.
Happy shooting everyone, and let there be light.