Although it has an 18 million pixel sensor, Canon's EOS 650D/Rebel T4i doesn't use the same CMOS device as other cameras in Canon's range. It uses a new Hybrid CMOS sensor that is designed to facilitate a combined phase detection and contrast detection autofocus system that operates during video recording and when Live View is activated.
Images and video are processed using Canon's Digic 5 14-bit engine, which enables a maximum continuous shooting rate of 5fps, that's up from the 3.7fps of the Canon EOS 600D.

Sensitivity has also been pushed, and the Canon 650D/Rebel T4i has a native range of ISO 100-12,800, which can be extended to ISO 25,600.
We have become used to smartphones, compact cameras and compact system cameras (CSCs) having touchscreens, but the Canon 650D is the first DSLR to feature one. Apart from the fact that it is touch sensitive, the screen is exactly the same as the one on the Canon EOS 600D.

This means it is a 3-inch 1,040,000-dot unit mounted on an articulating hinge, which makes it easier to shoot from a wide range of angles. The gap between the screen cover and the LCD is also filled with an optical gel to help cut down reflections.
Another interesting feature of the Canon EOS 650D's screen is that its menu display colour can be changed. There are five different options, four of which are just for preference, but one with red text on a black background that could be very useful for night-time shooting.

Hybrid AF

Like the Canon EOS 600D, in reflex mode the Canon EOS 650D uses a nine-point phase detection autofocus system. However, all of these points are cross-type with the new camera. The 600D only has one cross-type AF point, which is the centre of the frame. This should make the 650D's AF system more responsive than the 600D's, since it's better able to detect the subject.

Obviously we want to test a full-production sample fully before we pronounce judgement, but the early signs are good and the subject jumped quickly into focus at every AF point we selected during our time with the pre-production sample.
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In Live View and movie mode, the Canon EOS 650D is able to focus continuously using its Hybrid AF system. This is a first for an EOS camera. The phase detection part of this process is made possible by the presence of on-sensor pixels that are dedicated to informing the system.

Although Canon UK was unable to tell us how many pixels are used for phase detection AF, or how they are arranged, we're told that these pixels aren't on exactly the same plane as the imaging pixels. This suggests that unlike the pixels employed by Nikon's hybrid AF system in the Nikon 1 J1 and Nikon 1 V1, they are used solely for focusing and don't make up the image.

When the Canon EOS 650D focuses in Live View or video mode, it uses the new sensor phase detection system to get the subject close to being sharp, and then the contrast detection steps in to get it fully into focus.

At the time of our preview of the 650D, Canon wasn't able to comment on the reason for introducing the hybrid system, but we assume that it is designed to combine the speed of phase detection technology with the accuracy of contrast detection.

Image rating

We are pleased to find that it's possible to rate images out of five on the Canon EOS 650D, but we're a little disappointed that this function doesn't have a dedicated button like the Canon EOS 5D Mark III. Instead, the rating option is located in the menu. Nevertheless it's still fairly quick and very easy to use.

The great thing about Canon's in-camera rating system is that the information is stored with the image EXIF data, so the star ratings are displayed in software packages such as Adobe Photoshop Elements and Bridge. It makes reviewing images a really useful exercise, especially during a break in a lengthy shoot or after shooting long sequences.

You may not use the review mode to decide the very best image, but it provides a convenient way of identifying the most likely candidates.

New modes

With novice photographers in mind, Canon has introduced two new scene modes with the Canon EOS 650D: Handheld Night Scene and HDR Backlight Control. The first takes a sequence of four images and combines them using auto-aligning to get a correct exposure without blurring the subject. The aim of this JPEG-only mode is to break a longer exposure into four shorter exposures that enable the subject to be frozen.

Meanwhile, HDR Backlight control works in a similar way, combining three JPEG images into one auto-aligned composite with a correctly exposed background and foreground. The mode isn't intended to emulate extreme HDR effects, but to enable you to take correctly exposed images when the background is much brighter than the subject.

When we get a full production sample in for testing we will be interested to see if these modes render the images quicker than the pre-production camera, which took a few seconds.

It will also be interesting to see how the new Noise Reduction option performs. When selected, this mode triggers the camera to shoot and combine a sequence of four images into one with less visible noise. It sounds similar to a Photoshop technique which relies on the fact that most chroma noise is random.

Canon has also added two new Creative filters - Art Bold and Water Painting Effect - that can be added when reviewing images. These are easy to apply, but you may wonder why you can't select to use them at the shooting stage.

Video

No DSLR is complete without the ability to shoot video these days, and the Canon EOS 650D can record Full HD (1920 x 1080) movies at a variety of frame rates. A stereo microphone is built into the top of the camera, but there's also a port to connect an external mic. Furthermore, sound can be adjusted to one of 64 levels.

While this is all good news, you may be disappointed to learn that there is no headphone jack to enable sound to be monitored more easily than listening to the playback through the camera's speakers.

Canon has also included its excellent Video Snapshot mode. This enables footage to be shot in two, four or eight second-long bursts that can then be edited together in-camera.

For Canon, though, the big innovation that the EOS 650D brings to its video capability is full time autofocusing.

Source : techradar