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The Sony Alpha A55 and A33 – a new type of camera

Introducing the single lens translucent (SLT)

Sony SLT Alpha A55

Sony has developed an entirely new camera system, the SLT. The company has announced two SLT cameras, the Sony Alpha a55 and the Sony Alpha a33.

SLT stands for single lens translucent, and the two new cameras are smaller than typical digital SLRs. Both new Sony Alpha SLTs feature an Exmor APS CMOS sensor. The a55 offers 16.6Mp of resolution, while the a33 offers 14.2Mp.

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SLT – single lens translucent cameras

(please note, in the following video we state that light from the mirror is reflected onto the viewfinder – this is incorrect. The light is partially reflected upwards onto the autofocus system. The electronic viewfinder replicates the LCD screen, using the core sensor behind the mirror)


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We have seen a spate of mirrorless cameras with interchangeable lenses introduced in the past few months, including the micro four-third cameras from Panasonic and Sony, the NX10 from Samsung, and the NEX cameras from Sony.

The Sony Alpha a55 and a33 differ from these models as they do house mirrors. In a digital SLR the mirror directs the image to the viewfinder and then moves quickly out of the way to let the light hit the sensor. The mirrors in the new SLTs are fixed in place, and instead of moving they reflect some of the light to one sensor and let the remaining light pass through to a second sensor.

Sony explains that this allows the cameras to be faster than other models of a similar class. The company claims that the a55 can capture ten frames per second at full resolution, while the a33 can capture seven.

High resolution, adjustable LCD with Live View

The a55 and the a33 each feature a moveable 3-inch LCD which provides Live View, so pictures can be composed on the screen as well as through the electronic viewfinder. The LCD provides 1.15 million dot resolution, which should make the quality of the picture on the screen very crisp.

The new Alpha SLT cameras are both able to capture HD video footage at 1080i resolution. They are compatible with Sony and Minolta A-mount lenses, of which there are currently more than 30 available according to Sony.

The a55 and a33 offer ISO sensitivities between 100 and 12,800 and feature a host of manual controls that you’d expect from a digital SLR – including manual focus, exposure control and white balance adjustment.

3D pictures

The cameras recognise Sony’s MemoryStick Pro Duo memory cards as well as the more commonplace SD memory cards. Both cameras also feature the 3D Sweep Panorama mode that we recently looked at on the Sony NEX-3.

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