Friday, 8 June 2012

Canon EOS 650D

佳能发布EOS 650D:触摸屏、混合式AF
Canon's entry-level 'Rebel' series has enjoyed continuous success in its film and digital incarnations for more than two decades. Over this time these little SLRs have been increasingly improved and refined to the point that the company has seemingly struggled to find ways of making the latest iteration stand out from the last. Put the new EOS 650D / Rebel T4i side-by-side with its predecessor, the EOS 600D / Rebel T3i, and you could be forgiven for thinking that it's a very minor update, so similar are the bodies and specifications. But delve a little deeper and it's a more intriguing prospect than it first appears.

The headline specifications - 18MP CMOS sensor, 9-point AF sensor, 3:2 flip-out 1.04m dot screen are all familiar from the 600D. But each of these has been significantly improved and it's the fine detail that makes the 650D interesting - both as a product in itself and in what it says about Canon's view of the future.
佳能发布EOS 650D:触摸屏、混合式AF

佳能发布EOS 650D:触摸屏、混合式AF

The problem facing camera manufacturers is that the basic SLR concept is in danger of appearing anachronistic to the very people entry-level models are supposed to appeal to: users upgrading from smartphones and compact cameras who are now accustomed to setting up their shots using LCD screens rather than optical viewfinders, and who expect their camera to shoot video for upload to YouTube just as well as it captures stills for Flickr. The traditional SLR design, with its roots in 35mm film photography, has struggled to adapt to these demands, most notably offering poor focusing performance in Live View and video, and ergonomics centered around eye-level shooting.

Because of this, conventional entry-level SLRs have come under increasing pressure from mirrorless interchangeable-lens cameras, which offer a more compact camera-like user experience and superior video capabilities in smaller, more portable bodies. Meanwhile Sony's SLT cameras offer significantly improved live view and video in an SLR-like design by using an electronic viewfinder. Both types of camera offer features such as fast face-detection autofocus that compact-camera users now take for granted.

The EOS 650D appears to be designed to meet these challenges head on, with new features aimed at improving its live view and video performance. Firstly, it becomes Canon's first SLR capable of continuously tracking and maintaining focus on a moving subject while recording movies. This may not sound like a big deal - lots of cameras claim to be able to do so, with varying degree of success - but what matters is how it's implemented.

The EOS 650D has a new 'Hybrid CMOS' sensor that now includes pixels dedicated to phase detection autofocus (in a similar fashion to Nikon's 1 J1 and 1 V1 mirrorless cameras). The Hybrid AF system uses these to set the lens quickly to roughly the correct distance, then uses contrast detection AF to fine-tune focus. In principle, this should provide faster and more certain focusing for live view and video shooting compared to previous cameras that relied on CDAF alone.

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