Sony's A33 uses new translucent mirror technology in a digital camera for the first time. Is this the beginning of the end for DSLR cameras as we know them? That What Digital Camera Sony Alpha A33 review...

Product Overview

Overall rating:


Sony Alpha A33

Image Quality:85%
Overall score:89%


  • Super-fast continuous focus burst shooting, phase-detection live-view, excellent 1080i HD movie autofocus


  • Widescreen ratio LCD, EVF not for everyone, noisy kit lens (video can pick up lens zoom and focus noise)


Sony Alpha A33 Review


Price as reviewed:


Best Price from Reevoo



Sony’s latest SLT-A33 model with its Single Lens 
Translucent technology epitomises just how far camera technology has progressed. Near-identical to a DSLR in use, the compromise (as some may see it) 
is using the A33’s Electronic Viewfinder but 
the new technology’s resulting benefits mean that full-time phase-detection live view and ultra-fast 7fps continuous focus burst mode are available. Impressive stats indeed, but will the new ‘SLT’ category be the true undoing of 
DSLR cameras? The What Digital Camera Sony Alpha A33 review…

Sony Alpha SLT-A33 review – Features

Sony Alpha SLT-A33 product shot topThe Alpha A33 is the first of Sony’s new DSLT cameras, released alongside the higher-spec A55 camera. With a 14.2 megapixel APS HD CMOS sensor at its core and Sony’s sensor-based SteadyShot Inside image stabilisation system the A33 can record high-resolution images from ISO 100 right up to ISO 12,800.

It’s with the introduction of the translucent mirror technology that the SLT-A33 really picks 
up the pace however (see ‘How Single Lens Translucent Works’ on page 70 for a full explanation). Although not a ‘new’ technology as such (Canon’s EOS RT produced from 1989-92 being a case in point) it’s the 
first time a translucent mirror has been implemented in a digital system. As light 
can pass through the mirror it removes the necessity for it to move out of the way 
when taking a shot, meaning light bouncing from the mirror permanently feeds a newly developed 15-point (three cross-type) autofocus system, thus opening a whole 
new opportunity for super-fast shooting with full-time continuous autofocus. The A33 tops out at an impressive seven frames per second, though the ‘bigger brother’ A55 can amass 10fps and the forthcoming ‘A77′ (working title) is likely to be higher still.

The AVCHD 1080i high-definition movie mode takes particular benefit from this new full-time focus with a fully automated movie mode that can glides in and out of focus.

Sony A33 review test sample image

Sony Alpha SLT-A33 review sample image – click for full size gallery

With no optical viewfinder, the Sony Alpha A33 instead uses a built-in 1.15 million-dot Electronic Viewfinder (EVF) with a 100% field of view. The 920k-dot, 3in LCD camera on the rear is 
a 16:9 wideangle ratio and has a tilt-angle bracket meaning shots from over-head or waist-level points of view are possible, as is safe stowing with the screen-side facing into the camera for protection.

As well as fully manual modes, an Auto+ setting is capable of auto analysing a scene and selecting the best settings accordingly. There are plenty of other creative modes available too, including: D-Range Optimiser, Handheld Twilight, Sweep Panorama, an enhanced HDR Auto mode, plus the usual array of Creative Styles found across the current Alpha range.

Design – What Is ‘SLT’ & How Does It Work?

Sony Alpha SLT-A33 – Design

Without the pentaprism as a fundamental part of the design the A33 is smaller than a usual DSLR – but only ever so slightly in terms of height, to the point it’s barely noticeable. 
Most of the hand will comfortably fit around the grip, though your little finger may stray 
off the bottom of the body and that can be uncomfortable for long periods of use.

Sony Alpha SLT-A33 product shot front angleElsewhere the design is as expected from 
a usual DSLR – the mode dial to the top left can be quickly adjusted, while the opposite side has one-touch buttons for each of the Finder/LCD, D-Range, Movie, Exposure Compensation and AEL functions. The rear 
has a standard D-Pad and an Fn (Function) button above this for quick access to the 
most commonly used settings.

The main menu, accessed for the button behind the main mode dial, is the same as current Sony Alpha DSLR cameras. Divided 
into a number of sections with up to seven settings per page it avoids being too cramped and, as there’s no scrolling to located options, it’s fairly easy to find those more detailed settings. It’s really with the quick menu by using the Fn button that most control will be had, however, and this offers a comprehensive and easily navigable list of options.

What Is ‘SLT’ & How Does It Work?

The best way to explain how a translucent mirror system works is to compare it side 
by side to a DSLR system’s operation.

In a DSLR camera the light enters from the lens and bounces off the camera’s mirror into an AF sensor for fast phase-detection autofocus. Simultaneously light also bounces into a pentaprism that in turn feeds a preview image to the eye via an optical viewfinder (the pentaprism is there to flip the image from upside down and back to front to the usual way we see). Once the image is framed and the focus 
set a full shutter press will flip the mirror upwards and out of the way before the shutter itself fires to expose the image sensor (for the time period the shutter 
is set at) for the final image capture.

Sony Alpha A33 SLT technology
Sony Alpha A33 – ‘SLT’ (Single Lens Translucent) operational diagram

An ‘SLT’ camera, as Sony is naming the A33, also has a mirror construction – but, 
as this is translucent, 70% of light can permanently pass through, thus eradicating the need for the mirror to move at all during an exposure. Without the need for this slow mechanical movement it’s only the shutter that fires to make an exposure – and this can happen much more frequently, hence the A33’s super-fast 7fps shooting. The 
30% if light that bounces off the mirror 
is still available to reach the AF sensor for continuous phase-detection autofocus during live view mode – the first time this has been possible.

However the construction does not lend itself to an optical viewfinder due to the 
lack of available light that could reach a hypothetical optical viewfinder – this is 
why the A33 features a built-in electronic viewfinder in its place.


Sony Alpha SLT-A33 review – Performance

As the first of its type the SLT-A33 does a good job of avoiding too many teething problems. It’s comparable to the current Sony Alpha A560 DSLR also just released to market – meaning that, if the A33’s Electronic Viewfinder puts you off, a similarly-specced Sony DSLR offering is also available.

Sony Alpha SLT-A33 product shot rear screen on bracketThe A33’s 1.15 million-dot viewfinder may sound incredibly resolute but it’s worth noting that this is actually an 800×480 pixel resolution and, although detail is resolved at what’s among the best level available to market, there’s still a long way to go before any EVF reaches the detail we associate with high definition. A 2.76 million-dot version would equate to what a 720p HD TV screen is, whereas 6.22 million-dots would match 1080p. Admittedly, even camera LCD screens haven’t reached this level as yet, but consider how close the eye is to the finder and the level of detail becomes even more critical. Saying that, detail is one thing but it’s other factors that add both positive and negative points in use: Low light is very much the EVF’s enemy 
as the preview readily shows image noise and suffers from image lag and blur when panning or framing. In good light this is far less a problem, but there can be a subtle delay in 
the metering catching up with changes in light. On the upside, if more traditional expectations are brushed to one side for the moment, the new EVF does really benefit from the ability to overlay framing devices such as the dual axis level or grid pattern and a full time histogram preview and real time autofocus information can be relayed back. The EVF will be the one major ‘should I, shouldn’t I?’ moment when considering the A33’s purchase – and it’s likely that more new generation gadget-minded buyers will love its future-thinking, yet those with more experience with photographic kit may still take more convincing.

When not using the EVF, the 3in, 920k-dot LCD on the rear has the ability to rotate through a variety of angles to improve framing possibilities. The screen is of a standard high resolution and the only major qualm is its 16:9 ratio – ideal for shooting cinematic movies, 
but not so good for 3:2 stills images as black borders to the left and right make the preview a little smaller overall.

 Sony A33 review test sample image

Sony Alpha A33 review sample image – click for full size gallery

The A33’s movie mode is a positive step-up beyond what most DSLR cameras can achieve. The 1080i quality is good but it’s really with the new full-time phase detection autofocus that a true difference is made. When set into AF the camera can continuously and seamlessly focus with great accuracy during recording and it’s far faster than anything before it on this front. However, the autofocus is either on or set to manual with no half-way house for more complex control such as fixing focus mid-recording. For example, an interrupting subject walking through the frame will cause the camera to rapidly compensate and draw focus closer for that particular incident. The lens isn’t especially fluid in the zoom department either which can make for rather ‘clunky’ zooming if recording using the manual mode. And despite the rear LCD screen’s widescreen ratio it’s not possible to accurately pre-frame prior to recording as the 3:2 ratio is a different crop to the 16:9 movie one (it gives the appearance of having slightly ‘zoomed in’) when hitting the one-touch movie button which, upon being pressed, causes a brief half second blackout and delay prior to recording. However, despite the 18-55mm kit lens being audibly noisy there is an external microphone port available for more professional recording possibilities. On the one hand this is the best automated movie mode you could hope to buy, but in its initial state there’s plenty of room for improvement – something the forthcoming a700 replacement camera will more than likely take command of.

The all-new 15-point autofocus system has three cross-type sensors towards the centre for faster and more accurate use in both portrait and landscape orientation. Focus is steady and relatively quick, though the arrangement of the AF points is generally quite centralised on the sensor, so don’t expect more detailed edge-to-edge focusing. Objects with limited colour or contrast can also throw a spanner in the works with focus struggling to find a final point. An issue with many Sony DSLR cameras, as well 
as the A33, is the lack of an AF assist lamp. Instead the flash can pop up and pre-flash the scene to attempt to gain a read, but this is more distracting and less proficient than an 
AF lamp would be. With the 18-55mm kit lens on the front some impressively close-up macro shots were possible, whether shooting at the wide 18mm or longer 55mm end it was possible to focus on a subject as close as approximately 12cms from the lens.

Despite all the tech-wizardry on the inside, the A33 is caimed at both the newcomer as well as the more familiar enthusiast. In the menus 
a brief pause over a specific mode or option will bring up a simple explanation in English of what that mode does to make everything that bit more accessible. Leave the camera sat it playback mode unattended for about, though, and it’ll auto-play through your videos without so much as pressing a button.

Image Quality & Value

Sony Alpha SLT-A33 review – Image Quality

Sony A33 review – Tone & Exposure

As the translucent sensor can only pass some 70% of light to the sensor for final exposure, there is the obvious query as to whether this third of a stop loss in light affects final image quality and exposure. The short answer is ‘no’ as, unlike film of old, image sensors don’t have a fixed sensitivity as such. The A33 takes on board the loss of light and adjusts processing accordingly to compensate. Theoretically there could be a very slight variation in the resulting quality, but side by side testing with the NEX-3 showed exposure and ISO test chart images from both cameras to be very similar. It’s also worth noting that just because less light is reaching the sensor that you needn’t make any calculations differently to normal.

Final images are well exposed though this can occasionally be tricky to ascertain with precision on the LCD screen compared to when viewing on a computer screen.

Sony A33 review test sample image

Another much-talked about issue is the apparent ghosting that this new system causes – which can in very extreme and particular circumstances cause a subtle ghost to appear very closey to clipped-out highlights. However the ghost is much fainter than the full highlight and is also only off-set from the original by such a small degree that it won’t be noticeable in the majority of real world images. To test for this issue a series of openings were backlit on a lightbox yet there was no evidence of ghosting until some overexposure led to clipping in the highlights.

Sony A33 review – RAW/JPEG

The supplied Image Data Converter SR software reads the ARW-format Raw files and a future update from Adobe, Apple, etc will see full compatibility with Photoshop, Aperture and other programs.

Testing a variety of ‘standard’, long exposure and high ISO images the main difference between Raw files and their JPEG counterparts can be seen as the ISO sensitivity rises. At ISO 12,800 the Raw files have far less colour noise and the JPEG processing appears more grainy in an attempt to provide some perceptive sharpness. In all circumstances the JPEG files are processed with more contrast and sharpening.

Sony A33 review – Colour & White Balance

As well as the ‘Standard’ colour mode the A33 has a variety of other Creative Styles which can shift into ‘Vivid’, ‘Sunset’, ‘Portrait’ and ‘Black & White’. Not over-doing the number of options allows quick adjustment between the options and the subtle white-point shift made in each mode is pleasing. Black & White was also a lot of fun.

In normal Auto White Balance mode some indoor shots did appear a little orange and to the warm side, whereas some outdoor scenes had a slight lean towards a bluer cast. This only really becomes noticeable when making direct comparisons with competitor models as from image to image the white balance didn’t make any glaringly off-colour errors.

Sony A33 review – ISO Sensitivity & Image Noise


Image-noise-wise and results are very smooth and clean at lower ISO settings. Detail loss begins to creep in and above ISO 1600 this is fairly noticeable. However, despite both luminance and colour noise also becoming notable at the same sensitivity level it doesn’t prevent the majority of the ISO range from being useable – not a bad feat for ISO 12,800.

Sony A33 review test sample image
Sony Alpha A33 review – ISO sensitivity image noise test

A direct comparison to the Sony NEX-5 produced similar results in terms of image noise, which was as expected given the same sensors in both cameras.

Sony A33 review – Sharpness & Detail


As well as the 18-55mm f/3.5-5.6 kit lens this test also made use of a Sigma 50mm f/1.4 prime lens. The A33’s ability to resolve detail at lower ISO was very good, though noise reduction at higher ISO settings certainly caused a lessening of detail (high ISO noise reduction can be processed as ‘Auto’ or ‘Weak’ for JPEG images, or taken entirely into your own hands when shooting Raw). Macro shots taken with the 18-55mm kit lens were also impressively sharp.

Sony Alpha SLT-A33 review – Value

At around £650 with kit lens the A33 is around half the cost of the next nearest DSLR that offers a 7fps continuous burst capability. That’s 
a signifier of what the translucent technology will mean for someone on a more realistic consumer budget. There are, of course, still big differences between the lower level of control offered by the A33 and a highly customiseable professional DSLR, but the potential here is certainly excellent and the A33’s price point suitably eye-catching. Sat between the cost 
of a Nikon D5000 and a Canon EOS 550D, 
the Sony is well-positioned and offers a strong portfolio of features.


Sony Alpha SLT-A33 review – Verdict

Sony Alpha SLT-A33 product shot front angleThe A33 undoubtedly opens new doors and Sony’s clear-cut commitment to pushing new technology into the photo market is 
an interesting angle for a company looking for new approaches to capture today’s demanding audiences. Digital technologies are changing and it has to be said so are consumer’s expectations. While a year or 
so ago many noses would have turned at the mere suggestion of an Electronic Viewfinder the technology has come on 
in leaps and bounds. It may still not be perfect and, indeed, the EVF may be the A33’s greatest challenge. Though that sounds rather cynical as, in actuality, the A33 is an innovative, super-fast and top quality camera that feels much the same as using a ‘new age’ DSLR camera. There are one or two small improvements that could be made, but all things considered, this is new technology pushing the boundaries. The super-fast autofocus in live view and continuous focus burst modes actually work a treat. An exciting development that looks to be a step further towards the end of DSLR cameras as they once were – and not in a negative manner.


Sensor:14.2 Megapixel Exmor APS HD CMOS sensor
Output Size:4592 x 3056
Focal Length Mag:1.5x
LCD:3in, 921k-dot, tilt-angle, TruBlack LCD
DoF Prview:Yes
Max Flash Sync:1/160th
AF Points:15-point system with 3 cross type sensors
Built-in Flash:Yes, GN 10
Colour Temp Control:2500 – 9900 Kelvin
White Balance Bracket:3 frames, Selectable 2 steps
Colour Space:sRGB, Adobe RGB
Exposure Comp:Yes, ±2EV (in 1/3 stops)
Focusing Modes:Single, Automatic, Continuous, Manual Focus
Dust Reduction:Yes, Charge protection coating on Low-Pass Filter and electromagnetic vibration mechanism
Built-in Image Stabilisation:Yes, sensor-based Super SteadyShot
Weight:433g (no battery or card)
Movie Mode:1080i HD capture at 50 interlanced fields per second. AVCHD format.
Live Mode:Yes
Power:Rechargeable li-ion battery
Dimensions:124.4 x 92 x 84.7mm
Connectivity:HDMI (c-type), USB (standard mini connection)
Field of View:100%
Memory Card:SD / SDHC / SDXC / Memory Stick Pro
Viewfinder Type:Electronic Viewfinder; 1.15M-dots 100% field of view
Drive Mode:Single, Continuous, 10 seconds and 2 seconds Self-timer, Max.7 fps in Continuous Advance Priority AE, max. 6 fps in Drive Mode
White Balance:Daylight, Shade, Cloudy, Incandescent, Fluorescent, Flash, Setting the color temperature
Metering System:1200-zone evaluative metering
Exposure Modes:P, A, S, M, Continuous Advance Priority AE, Sweep Panorama, Scene, Flash Off, Auto, Auto+
Compression:Fine or Standard (JPEG)
Shutter Speeds:30 – 1/4000th second (plus Bulb)
File Format:JPEG, RAW (ARW), RAW + JPEG
Lens Mount:Sony A-mount (Minolta-fit)
  1. 1. Sony Alpha SLT-A33 review - Features
  2. 2. Design - What Is 'SLT' & How Does It Work?
  3. 3. Performance
  4. 4. Image Quality & Value
  5. 5. Verdict
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