Sony Alpha A33 and A55V Preview
On August 23, 2010, Sony announced two new APS-C digital cameras, the SLT-A55V and the SLT-A33. Both feature what Sony are calling “Translucent Mirror Technology”. What this appears to be is the use of a semi-reflecting fixed pellicle mirror, such as Canon has previously used on camera such as the EOS RT.
I’m a little confused by Sony’s terminology since “Translucent” is defined as “permitting light to pass through but diffusing it so that persons, objects, etc., on the opposite side are not clearly visible”. I’d have to assume that the mirror in the A33 and A55 does not diffuse the light, but rather allows some light to pass through to the sensor and directs some light onto the AF (and perhaps metering?) hardware. That’s technically a semi-transparent (or semi-reflective) mirror, not a translucent mirror. But I guess Sony can call it whatever they want to!
Using this technique allows continuous phase detection auto focusing and it also permits faster frame rates since there is no time delay while the reflex mirror moves up and down. In the Canon EOS RT the cost of this was, if I recall correctly, about 2/3 of a stop of light, since some light which would normally reach the film (or in this case sensor) is used to illuminate the AF sensors.
Rather than using an optical viewfinder, both the A33 and A55V use an electronic viewfinder. This brings into question whether they can actually be called DSLRs, since they don’t actually have a reflex mirror for optical viewing. Sony refers to them as “interchangeable lens digital cameras”.
The differences between the A33 and A55V are:
- The A55 has a 16.2MP sensor while the A33 has a 14.2 MP sensor.
- The A55 has built in GPS
- The A55 costs more ($750 vs. $650)
Both feature the ability to shoot at 10 frames/second (with continuous phase detection AF), plus the ability to shoot 1080l HD movies, also with continuous phase detection AF (a first for any interchangeable lens digital camera). Both feature a 3" articulated (tilt and swivel) LCD and both cover the ISO range form 100 to 12800 (with 25600 possible in HDR mode).
Both these cameras are certainly an advance from the point of view of video (and high speed) shooting. For the first time in a camera of this class, phase detection AF will operate while shooting video. Phase detection AF is the type of AF normally used in DLSRs for still photography. It’s faster and more accurate than contrast detection AF, which up to now has been the only option for continuous AF in Live View and video modes.
The high speed still operation (10 frames/sec) is also impressive, matching the speed of the Canon EOS 1D MkIV, though almost certainly not with the same degree of AF tracking ability. Sony specify the buffer of the A33/A55 should hold around 20 RAW images or 35 JPEGs
Here’s a copy of the Sony Press Release:
DSLR REDEFINED: SONY INTRODUCES NEW CAMERAS POWERED BY WORLDS FIRST
TRANSLUCENT MIRROR TECHNOLOGY ENABLING SIMULTANEOUS AUTO FOCUS AND CAPTURE IN AN
INTERCHANGEABLE LENS DIGITAL CAMERA
New Models Offer Continuous Phase Detect AF during 10 fps High-Speed Shooting and Full
HD Movie Shooting
SAN DIEGO, August 23, 2010 Sony today introduced two new a
cameras (models SLT-A55V and SLT-A33) that adopt Sonys newly-developed Translucent
Mirror Technology, which achieves the highest-level of auto focus speed for both
still image and movie shooting.
Translucent Mirror Technology provides performance previously unattainable with
traditional DSLR technology. Using the new technology, the a55 and a33 models can
continuously and quickly focus (with TTL phase-detection) while shooting stills and
recording videoeven in full HD, allowing desired moments to be captured in tack
sharp focus, high-definition video. They can shoot continuously at up to 10 frames per
second on the a55 (and up to seven on the a33), achieving shooting speeds that are the
fastest in the industry for an APS-C size sensor-equipped interchangeable lens cameras
This is the most innovative Interchangeable Lens Digital Camera that Sony has
ever created, said Kristen Elder, director of the digital imaging business group.
Our Translucent Mirror Technology is one of the most significant SLR structural
changes in more than a decade.
By displaying the images received by the Exmor APS HD CMOS Sensor, picture
quality of the cameras live view image has enhanced drastically. Coupled with the
quick and accurate phase detect AF and 100 percent coverage Tru-Finder electronic
viewfinder, the Quick AF Live View feature has been further advanced.
Translucent Mirror Technology
Both cameras are equipped with a translucent mirror, which enables light passing
through the lens to be simultaneously received by the image sensor and the auto focus
sensor, allowing continuous shooting and continuous focusing at speeds never before
possible. The a55 offers the world’s fastest 10 fps high-speed burst shooting with
continuous AF (TTL phase-detection) in an interchangeable-lens digital camera with APS-C
Because of its structure, the Translucent Mirror Technology does away with the
motion of raising and lowering the mirror. The absence of the moving mirror mechanism
contributes to making the whole body size significantly compact compared to traditional
By eliminating the need to raise and lower the mirror between shots, the technology
makes it possible to achieve focusing while images are captured. Existing systems can only
focus in the interval between image capture, limiting the ability to track fast moving
subjects. The cameras also have continuous Advance Priority AE Mode and will automatically
adjust for the best exposure to help you get the most professional looking results.
High-Speed Capture with Auto Focus
Additionally, a newly developed 15-point AF system assures ultra-fast, high precision
focusing. The high-speed shooting with continuous Phase Detect AF tracks rapidly moving
subjects accurately. You can capture the decisive moments that you might have otherwise
Creative Video Capture
The continuous phase detect AF also works in movie shooting for the first time in the
world. The Translucent Mirror Technology also allows the a55 and a33 to be the first
cameras to ever maintain continuous phase detection AF while recording Full HD AVCHD
video. With fast, precise phase detection AF continually tracking subject movement, even
fast action and subjects that move quickly towards or away from the camera are easy to
keep in focus.
With a large 16.2 megapixel (for the a55) and 14.2 megapixel (for the a33) Exmor
APS HD CMOS sensor, background defocusing effects can be easily captured. The APS-C sensor
size is nearly 20 times larger than a traditional compact camcorders 1/2.88 type
image sensor, providing more creative control.
Compatible with all A-mount lenses, video and photography enthusiasts alike can choose
from macro to telephoto lenses to achieve their desired artistic effect.
Full-time Live View
Full-time Live View offers unprecedented freestyle shooting versatility with fast,
precise AF using either the viewfinder or LCD monitor. The a55 and a33 have a fully
articulated 3-inch 921,600 Xtra Fine LCD with TruBlack technology with 100 percent
The Tru-Finder eye-level viewfinder provides an unprecedented combination of 100
percent coverage and 1.1x magnification for easy and natural framing. By combining
Translucent Mirror and Tru-Finder technologies, a33 and a55 are the first interchangeable
lens digital cameras to offer movie recording with the familiar eye-level shooting style
a significant advantage in fast moving and extreme lighting conditions (bright
sunlight and low-light situations).
The variable angle tilt LCD is adjustable to accommodate shooting from low or high
angles. The electronic view finder has a high-resolution effective 1.15 million dots
conversion Xtra Fine LCD display, is bright and easy to see even in low light, has a
selectable shooting parameter display and shows the effects of exposure and white balance
Advanced Shooting Features
With an Exmor APS HD CMOS sensor, BIONZ® high-speed image processing engine and
ultra-high ISO sensitivity (ISO 100-12,800), the a55 and a33 cameras offer advanced
shooting features. These make it easy to get the best shot, even in difficult lighting
Auto HDR shoots and combines three frames into a single high dynamic range (HDR) photo
with rich shadow and highlight detail. Multi frame NR shoots and combines six frames into
a single photo, enabling smooth low-light imaging at half the noise level. Hand-held
Twilight shoots and combines six frames into a single photo, suppressing blur to enable
clear night-scene imaging without a tripod or flash.
3D Sweep Panorama technology creates two images from a single frame, enabling
panoramic photos to be viewed in 3D on compatible 3D systems and other devices that
support 3D technology. Using the a55 model, built-in GPS capability enables global
positioning coordinates to be recorded along with the date and time. HDMI
connectivity enables stunningly beautiful PhotoTV HD display of images on compatible Sony
AUTO+ (Advanced Auto) mode offers the same benefits as Auto mode and more, resulting in
cleaner, more dynamic pictures and fewer missed shots. The camera automatically recognizes
the correct scene mode, then quickly shoots and combines up to six shots to produce images
with greater clarity, optimum dynamic range using Auto HDR technology and lower image
noise using 6 shots layering technology.
The new cameras accept both Memory Stick PRO Duo (including Memory Stick PRO-HG
Duo) and SD (including both SDHC and SDXC formats) media (all sold separately). With
a 30MB per second transfer rate, Sonys Memory Stick PRO-HG Duo HX offers the best
performance of all memory cards whether in continuous shooting mode or transferring data
to other media.
A new dedicated microphone (models ECM-ALST1 and ECM-CG50) will also be available.
Pricing and Availability
The a55 and a33 cameras will cost about $750 and $650 (respectively) for the body only
and about $850 and $750 (respectively) for the body and 18-55mm zoom lens. The a33 camera will be available in September and the a55 model will be available in October.