August 27, 2010

Transparently Sony for HD snappers

Sony has announced new HD DSLR cameras that record 1920x1080 video, with some interesting new features and the usual bitrate stupidity…

The Sony A580 and A560 models will be its first DSLRs to do video of any sort. It also has two Single Lens Translucent cameras (DSLRs without the reflex), which use a pericle mirror to deflect some light up to a fast phase-detection auto-focus sensor while still letting about 70% of the light through to the image sensor.

Sony Alpha A580
The 16.2 megapixel A580 and 14.2mp A560 use Exmor APS-C HD CMOS sensors with enhanced Bionz processors. Both have 3-inch pivoting LCDs and good low-light capabilities (up to ISO 25,600). The €900 A580 will be available in October and the €800 A560 ships early 2011.

The fixed, semi-transparent mirror in the SLT A55 and SLT A33 (pictured top) means that they can use their faster, more accurate phase-detection AF sensor all the time, including video mode. HD DSLRs can only use phase-detection in stills mode (while the mirror is down), because the mirror has to be locked up for video, which requires switching to slower, less accurate contrast detection AF (which isn't even available during recording on some cameras and is so slow it is almost unusable on others).

Typical Sony A55 users
Of course, users should really be skilled enough not to have to use any fancy auto focus. They should be capable of doing everything in manual, including, no doubt, hand cranking the shutter…. :^)  While manual focusing is probably the best way to shoot many subjects, it isn't always easy to focus precisely with stills lenses, especially if you want to adjust it seamlessly during a recording, because the focus mechanisms aren't as precise as they are on a dedicated cine lens – and the cameras don't have the focusing aids you might expect on a professional camcorder (such as peaking). Most DSLRs don't give you much manual control over any functions during recording (these only allow you to adjust the aperture), so the quality of their automatic controls is important.

As the SLT cameras don't have to retract the mirror to take stills, they can also be used at high frame rates for photography (up to ten frames per second on the A55), and the cameras are significantly smaller than DSLRs. Although less light gets through to the CMOS sensor, this reduction is only the equivalent of about half a stop.

Sony A33 makes a splash
The 16.2mp A55 ($749 October) and 14.2mp A33 ($649 September) have a 3-inch articulated LCD, and go up to 12,800 ISO. All the cameras have HDMI output and mini-jack stereo microphone input.

All four Sony cameras record 1080 50i/60i (25p/30p capture on the sensor), using AVCHD at only 17Mbps, which is daft. When even its Handycam camcorders can record AVCHD at 24Mbps, why is Sony crippling these cameras by limiting them to 17Mbps?

Even so, it looks as if they can record reasonable video – have a look at the ever-excellent DP Review in-depth review of the A55, which has unconverted files you can download – the sixth clip is a great example of the jello effect you can get with a rolling shutter.

Given that for a similar price you can buy Canon's EOS 550D, you'd be nuts to buy any of these Sony cameras if you want to shoot video; but as consumer stills cameras (or even prosumer in the case of the A580/A560), which also shoot home videos, they could be worth considering.

By David Fox

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