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Sony Alpha SLT-A33 Gordon Laing, February 2011

Click here to find out about the Sony Alpha SLT-A33's Movie Mode


Sony Alpha SLT-A33 lenses, focus, sensor & drive

 
   

The Sony Alpha SLT-A33 employs an A-mount for lenses and is compatible with the complete range of Sony lenses and third party models designed for the Sony or Minolta AF systems, including Sony's DT models. All lenses attached to the SLT-A33 can exploit the camera's built-in SteadyShot stabilisation, and since the A33 employs the same physically sized sensor as previous cropped-frame Alphas, all lenses effectively have their field of view reduced by 1.5 times.

It's important to add the phase-change AF system will also work with any Alpha lens. This may be an obvious statement if discussing an Alpha DSLR, but it means the SLT-A33 can continuously autofocus while filming video with any lens in the Alpha catalogue. This gives it a key advantage over many mirrorless EVIL cameras, which have smaller native lens catalogues to start with and often suffer from further restrictions regarding continuous AF.

 
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The counter-benefits of EVIL camera systems are quieter focusing from native lenses and the opportunity to exploit a massive range of third party lenses via adapters. But again the native lens selections for EVIL cameras currently remains small - especially for Sony's own NEX E-system - and once you mount third party lenses, they become manual focus only. The big benefit of the A33 over EVIL cameras, particularly those from Panasonic, is full AF compatibility with a large existing lens catalogue, and of course the added benefit of enjoying stabilisation with each and every one.

Depending on your region, the SLT-A33 is available body alone, or in one of two lens bundles with either the DT 18-55mm f3.5-5.6 SAM alone or this and the DT 55-200mm f4-5.6 SAM in a twin lens kit. The DT 18-55mm SAM looks, feels and operates much like rival 18-55mm kit lenses. As you zoom from wide to telephoto, the barrel retracts and extends again, with the physically shortest position around the 35mm focal length. There's no manual focusing ring to speak of, so like other kit lenses, you'll be grabbing and rotating the narrow end section. This section therefore also rotates during autofocus, which means users of polarising filters may need to readjust after focusing.

The SAM designation refers to a built-in 'Smooth Autofocus Motor'. Don't expect equivalent speed and operating noise to Sony's higher-end SSM lenses though - in terms of focusing speed and mechanical noise the DT 18-55mm SAM is pretty much the same as Canon's EF-S 18-55mm IS. If you fancy a classier general-purpose zoom from day-one, we'd recommend the Carl Zeiss DT 16-80mm f3.5-4.5, a lens which delivers excellent image quality albeit without a fast and quiet SSM focusing motor. If you're filming video without an external microphone, you need to be aware of focusing noise too, as many of the Alpha lenses will be heard quite audibly by the built-in microphones.

 
 

Like all Alpha DSLRs before it, the SLT-A33 is equipped with sensor-shift image stabilisation to combat camera-shake. This moves the entire sensor platform in two axes and is branded by Sony as SteadyShot. Sony claims the system is good for between 2.5 and 4 stops of compensation depending on the lens and shooting conditions, and like recent Alphas it's enabled or disabled from a menu option rather than with the physical switch of earlier models.

As with all sensor-shift stabilised solutions, the major benefit is that it works with any lens you attach, new or old, wide or long, prime or zoom. As a 100% Live View system, the A33 technically could preview the stabilising effect on-screen or through the viewfinder, but in our tests, it didn't appear to be applying it until the picture was actually taken. If this is the case, it may save battery power, but feels like a missed opportunity when composing with longer lenses. Like the Alpha DSLRs before it though, the SLT-A33 does at least have indicators in the viewfinder to show how hard the system's working, or when it's gone beyond its capabilities.

To test the effectiveness of the SLT-A33's built-in stabilisation we took a serious of photos with the 55-200mm zoomed-into an equivalent of 300mm where traditional photographic advice would recommend a shutter speed of approximately 1/300 to eliminate camera shake. Our sequence started at 1/320 and reduced by one stop each time until 1/20. You can see results at 1/20 with SteadyShot disabled and enabled below.

 
Sony Alpha SLT-A33 SteadyShot with DT 55-200mm at 200mm
100% crop, 1/20, 55-200mm at 200mm (300mm equivalent), SS off   100% crop, 1/20, 55-200mm at 200mm (300mm equivalent), SS on

   

With SteadyShot stabilisation disabled, the slowest shutter speed we could handhold a sharp result at 200mm on the conditions of the day was 1/160. With SteadyShot enabled, we managed a pretty sharp result at 1/20 moments later, corresponding to three stops over the unstabilised version, or four over what conventional wisdom would recommend. This is a good result for the SLT-A33, which lest we forget can apply stabilisation to any lens you attach, making it more flexible than rivals which relay on lenses with optical stabilisation. It's a shame Sony doesn't appear to offer a preview of the stabilisation as you compose the shot - which would have been handy at longer focal lengths - but having it built-into the body remains a very valuable facility.

 

Sony Alpha SLT-A33 focusing

The Sony SLT-A33 boasts unique autofocusing capabilities: it may employ 100% Live View composition, but couples it with the quick and continuous phase-change autofocus system of a traditional DSLR.

 
   

Sony achieves this unique combination with a fixed, semi-reflective mirror. Most of the light passes through the mirror to expose the main sensor and deliver Live View, but a smaller portion is always reflected up to a phase-change AF sensor - the Sony promotional diagram, right, illustrates the optical path. This is unlike a DSLR where the mirror flips-up to expose the main sensor during Live View, thereby bypassing the phase-change AF system entirely. This is why conventional DSLRs are forced to use contrast-based autofocus during Live View, which is normally much slower.

Note Sony refers to this technology as a translucent mirror - hence the acronym SLT for Single Lens Translucent - but it's arguably better to refer to it as a semi-reflective or semi-transparent mirror. While translucent can be used to describe something that's semi-transparent, most primary definitions describe it as 'transmitting light but causing sufficient diffusion to prevent perception of distinct images' - just like a frosted bathroom window, and thereby obviously not ideal for photography. The correct technical name for the mirror in the SLT cameras is a 'pellicle' type although for the purposes of this article we're happy to refer to it as a semi-reflective mirror, as that's exactly what it's doing: reflecting a small amount of light, but allowing the lion's share to pass through to the imaging sensor.

 
 
 
 

Terminology aside, the Sony A33's autofocusing in Live View is a revelation, with the 15-point AF system snapping onto subjects as quickly as composing with the optical viewfinder on a traditional DSLR. Better still, unlike the contrast-based systems on most Live View cameras, the A33 confidently supports continuous AF for tracking subjects. Technically it can even beat a traditional DSLR in that regard, as the semi-reflective mirror ensures the A33 keeps focusing even as you take the shot, whereas a DSLR must briefly switch to a predictive system while its mirror is raised.

Where the system really impresses though is for video. Since the phase-change AF system is always active, it can be used to deliver quick and continuous autofocus while filming. This is unlike most video-equipped DSLRs which either perform a laborious contrast-based search every few seconds, or don't bother at all and force you to manually pull-focus instead.

The phase-change AF system of the SLT-A33 isn't just faster than most contrast-based systems - it's cleverer too. One of the rarely-mentioned benefits of phase-change AF is its ability to know which way to turn the focus to achieve a sharp result. Under ideal conditions this allows it to focus straight onto the subject without drifting back and forth to confirm. In comparison a contrast-based system has to briefly go beyond the point of focus, before returning again to confirm it. This back and forth process is known as searching or hunting, and can be very distracting in video. In contrast, if the A33's AF system can successfully lock-onto a subject, it'll do so with the minimum of fuss.

This is all very impressive, and we have more information on the video autofocus in our movie mode section below, but Sony's SLT implementation is not without its downsides. Most obviously the semi-reflective mirror always reflects approximately 30% of the incoming light to the phase-change sensor, leaving less for the imaging sensor to work with. This means greater amplification is required to achieve the same sensitivity as a conventional camera system using the same sensor, and hence higher noise levels. Some owners have also reported ghosting issues with the semi-reflective mirror under certain conditions, although we didn't experience those in our tests; that said, astro-photographers or night cityscape fans capturing bright details against a dark background should do further research.

A lesser-known disadvantage is phase-change AF systems rely on very strict manufacturing tolerances. If the AF and imaging sensor distances don't exactly match, you could find yourself with a slightly out-of-focus subject even when the AF sensor reports perfection. The effect of lenses front or back-focusing is fairly well-known for traditional DSLRs, but has never been an issue for Live View cameras until now as they've always taken contrast-reading direct from their imaging sensors. The Sony SLT cameras lull you into a false sense of security with their 100% Live View composition, but thanks to their phase-change AF sensors are equally susceptible to lens calibration issues as conventional DSLRs.

Sony's so confident of its phase change system that it doesn't offer a contrast-based alternative, nor any kind of AF fine-tuning or micro-adjustment. It's literally blind faith, and as we discovered, sometimes misplaced. Our A33 sample suffered from occasional focusing issues and inconsistencies during tests where a number of images were slightly out of focus, despite the AF system assuring the contrary. This occurred under strict conditions where the camera was mounted on a tripod, and the static subject placed directly under an AF point at a distance of about 15m. In each case, the camera reported a focused image, but while some were perfectly sharp, others were slightly off.

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We tested the A33 side-by-side with the Panasonic Lumix GH2, which employs a traditional contrast-based AF system. Since contrast-based systems take measurements directly from the imaging sensor, they eliminate any front or rear focusing issues. Problems can still occur, but it's revealing that under the same test conditions, the Lumix GH2 enjoyed a much higher success rate with focusing then the A33.

Now this may just be a calibration issue with our particular sample, but like all phase-change systems, it's important to know they're not infallible. Contrast-based systems for all their speed issues can be more consistent and accurate.

Some are quick too. Panasonic has put a lot of effort into proving contrast-based systems can be as fast or even faster than phase-change systems, and its Lumix GH2 is one of the quickest around. Indeed in our tests with their respective kit lenses, the GH2's contrast-based AF was visibly faster than the Sony A33, while again avoiding calibration issues. It was also much quieter in operation.

The caveat here is the GH2 is only quicker for Single AF modes. Switch both cameras to Continuous AF and the A33's phase-change system will more confidently track fast action with less searching, although it has to be said, the GH2 wasn't far behind.

The bottom line is the SLT-A33 may have one of the most innovative AF systems around, and one which thrashes the Live View and movie focusing on traditional DSLRs, but don't assume it's infallible, nor the overall best out of the current hybrid cameras.

 
 
 
 

Looking at the actual focusing options in more detail, the SLT-A33 lets you set the AF mode to AF-S, AF-C or AF-A (automatic), and the AF Area to Wide (automatically selecting from all 15 AF points), Spot (which only uses the Central point), or Local (where you manually choose one of the 15 points).

There is the option to enable Face Detection, but while the camera's software will follow subjects with a familiar square frame on-screen, it won't actually focus on them unless they fall behind one of the fixed 15 AF points. Remember the A33 only has phase-change AF at its disposal, so it has no means to auto-focus on anything outside of its 15 AF points.

This certainly has the potential to confuse, as while the camera may successfully place a frame over a face and follow it around the frame, it might not actually be able to focus on it. This is slightly misleading in our opinion and could lead to some disappointment when photos of people aren't always as sharp as you'd expected.

To be fair, the A33 will only turn the face frame green to confirm focus when it does fall over an AF point, but many will assume it's simply working like Face Detection on a contrast-based system, which can track and focus across most of the frame. This is another area where the Lumix GH2 takes the lead, as its conventional contrast-based AF system can track and focus on faces almost anywhere on the frame, and as mentioned above, lock-onto them quickly.

Finally, the SLT-A33 offers magnified focusing assistance, although you'll need to enable it first in a menu. Once enabled, you press the Trash button to superimpose a frame on the screen. Next move the frame to the desired area using the rocker control, before pressing Trash again to magnify it by 7 times or again for 10 times - see screen-grabs left

We used this facility in our test shots to confirm the phase-change system had got it right, or to correct it if it was slightly off, as was sometimes the case in our High ISO Noise composition.

 

Sony Alpha SLT-A33 sensor and processing

 
 
 
 
 

The Sony Alpha SLT-A33 is equipped with a 14.2 Megapixel Exmor CMOS sensor, measuring 23.4x15.6mm. Like Sony's other cameras to employ APS-C sized sensors, the field of view is reduced by 1.5 times, so the effective focal length of all lenses is effectively multiplied by 1.5 times - so the 18-55mm SAM kit lens delivers coverage equivalent to 27-83mm in full-frame terms.

The SLT-A33's sensor delivers 3:2 shaped images with a maximum resolution of 4592x3056 pixels; lower resolution options are available at 7.4 and 3.5 Megapixels, along with cropped 16:9 options at 12, 6.3 and 2.9 Megapixels. Images can be recorded with Fine or Standard compression, or in Sony's 'ARW' RAW format, either by itself or accompanied by a Fine JPEG. Best quality Large Fine JPEGs typically measured around 5MB each in our tests, but for complex scenes increased to around 8MB; RAW files weighed-in at around 14.5MB each.

The SLT-A33's sensitivity ranges from 100 to 12,800 ISO in single EV increments, although switching to Multi Frame Noise Reduction adds an extra high 25,600 ISO option. We'll discuss Multi Frame Noise Reduction in more detail below, and you can of course see comparative results demonstrating it and the standard sensitivity range in our High ISO Noise test pages.

Contrast, saturation and sharpness are applied in a range of +/-3 steps using a selection of five colour Creative Styles. There's also a Black and White option, although this simply dispenses with saturation and sadly doesn't replace it with any coloured filter effects.

Like all Sony cameras, the SLT-A33 offers a variety of contrast-enhancement options applied with its Dynamic Range Optimizer, or DRO for short. DRO can be set to Auto, or to one of five manual levels from weak to strong.

To put the A33's DRO to the test we photographed our standard low-light composition (which contains dark shadows and saturated highlights) using each of the settings. Below are examples showing the extremes of the range, with DRO disabled on the left and set to the maximum Level-5 on the right. It's clear from both the photo and the histogram below right how DRO has boosted the shadow areas, along with brightening mid-tones, although the backlit windows remain saturated.

     
Sony Alpha SLT-A33
DRO Disabled
 
Sony Alpha SLT-A33
DRO Level-5
     
 
0.8 secs, f8, 100 ISO
0.8 secs, f8, 100 ISO

The DRO options can be accessed via the Fn menu or the dedicated D-Range button. From there you can also select the A33's High Dynamic Range, or HDR options. The HDR mode shoots three different exposures in quick succession, then automatically combines them into a single image. You can either choose the Auto HDR option, or six manual settings which set the exposures from 1 to 6EV apart. Note HDR is not available when shooting in RAW.

To put the A33's HDR to the test we photographed our standard low-light composition (which contains dark shadows and saturated highlights) using each of the settings. Our Sony SLT-A33 HDR results page shows examples of each HDR setting, but for a quick comparison, below are two images showing HDR off and then set to the maximum 6EV setting. Looking at the histogram alone, you'd be forgiven for thinking the A33's Auto HDR has simply squashed the DRO Level 5 range seen above with a greater peak in mid-tones. But looking at the actual images reveals the HDR version has retrieved some of that lost highlight detail from the previously saturated windows. This illustrates the benefit of the HDR mode over single-frame DRO, although to better protect highlight detail, you may prefer to use it in conjunction with a little negative exposure compensation.

     
Sony Alpha SLT-A33
DRO / HDR Disabled
 
Sony Alpha SLT-A33
HDR 6EV
     
 
0.8 secs, f8, 100 ISO
0.8 secs, f8, 100 ISO

While HDR aficionados may have preferred an additional option to shoot more than three frames (or have broader bracketing options for HDR assembly on their computers), it remains a very powerful feature to find in-camera. The maximum 6EV range is particularly impressive, although most will find the more modest options deliver a subtler and more realistic effect; again see our Sony SLT-A33 HDR results page for examples of each setting in action.

 

Sony Alpha SLT-A33 shooting modes

 
 
 
 

The Alpha SLT-A33's mode dial offers the choice of Auto, Flash Off, Auto+, SCN, Sweep Shooting, and Continuous Advance Priority AE, in addition to the traditional Program, Aperture Priority, Shutter Priority and Manual modes.

Auto delivers a fairly basic automatic exposure mode without, as far as we can tell, any scene detection; Flash Off is the same, but forces the popup flash not to fire.

The Auto+ mode is where it starts to get interesting, as it not only employs scene detection to choose one of nine presets, but also includes two of the A33's more innovative multi-frame modes: Handheld Twilight and Auto HDR. This builds upon earlier Alpha models which may have shared some of the same modes, but forced you to deliberately find and deploy them yourself. Now the Auto+ mode can exploit their often excellent results as it sees fit.

Now when you're handholding photos in very dim conditions, the SLT-A33 could opt for Handheld Twilight mode to protect from camera shake while also reducing visible noise. Meanwhile if the camera detects a composition with large amounts of very dark and light areas, like a strongly backlit building or landscape, it'll select Auto HDR. Each mode captures six or three frames respectively before combining them into one, so obviously there's a risk an Auto+ user might begin to lower the camera while it's still shooting. In both cases though, the camera clearly states its intention, so there shouldn't be too many surprises.

In practice we found the SLT-A33 playing a little safe and only deploying these modes in fairly extreme conditions when we'd have personally selected them a little sooner. But you do of course have the chance to activate them yourself whenever you want, and we're just pleased to find Sony adding them to an Auto mode in any shape or form.

To illustrate Auto+ in action we shot the following scene in Auto and Auto+ modes, deliberately adjusting the composition until the latter selected its Auto HDR mode. This may be a little contrived, but illustrates how Auto and Auto+ evaluated and dealt with the same strongly backlit scene.

     
Sony Alpha SLT-A33
Auto mode
 
Sony Alpha SLT-A33
Auto+ mode (with Auto HDR)
     
 
1/640, f8, 100 ISO
1/640, f8, 100 ISO

 

 
 
 
 
 
 
 

If you like the automatic life, but prefer to point the camera in the right direction, the SCN position offers eight presets including Portrait, Sports Action, Macro, Landscape, Sunset, Night View, Handheld Twilight and Night Portrait; each is accompanied by a page which describes the mode with a sample image of how it might be used.

The most interesting of the Scene presets is Handheld Twilight mode, or HHT for short, which fires-off six frames in roughly one second before combining them into a single image. HHT is designed for static subjects in low light and combines its frames to reduce visible noise. The sound of the shutter firing six times in quick succession is far from discreet and guarantees some head turning from anyone within ear-shot, but the results can be excellent.

The only problem with Handheld Twilight is it's fully automatic with no control over the shutter, aperture or sensitivity. Wouldn't it be nice to enjoy the same multi-frame noise reduction in any mode, such as Program or Aperture Priority, where you could also choose the sensitivity? Well now you can with the SLT-A33 using its appropriately-named Multi Frame Noise Reduction settings.

You'll find these at the top of the main ISO page in a scrolling menu. Simple choose 100-25600 ISO in single EV increments, or Auto, and the A33 will fire-off six frames and combine them into one to reduce visible noise. This is a very welcome addition to the A33 to say the least and more than makes up for the loss of Anti Motion Blur mode.

Indeed we'd say Handheld Twilight and the new Multi Frame Noise Reduction modes are so important and effective that we've devoted entire results pages to each. They're a key benefit the A33 has over the competition and are some compensation for the semi-reflective mirror reducing the effective sensitivity of the camera. See our Sony SLT-A33 Handheld Twilight results and Sony SLT-A33 Multi Frame Noise Reduction results.

Returning to the main mode dial, the next option is Sweep Shooting. This refers to Sony's cunning panorama facilities which again exploits the quick continuous shooting capabilities to fire-off a burst as you pan the camera across a scene. The camera then automatically stitches the frames into a single panoramic photo within mere seconds.

Like the NEX cameras before it, you can choose the panning direction from left to right, right to left, or vertically from down to up or up to down. You can also select between standard or extra wide image sizes, and again the resolution matches the NEX cameras: 8192x1856 or 12416x1856 pixels for horizontal panoramas, and 2160x3872 or 2160x5536 pixels for vertical panoramas. If preferred you can shoot horizontal panoramas with the camera held in the portrait orientation by simply selecting the vertical panorama option.

In use the Sweep Shooting is certainly impressive. As you shoot, a frame on the screen guides you through the pan and asks you to repeat if you're moving too fast. If you stop moving before the maximum image width, the camera simply records a grey area you can crop-out later. At first glance the results look great, although like most panoramic stitching there can be errors depending on the subject, distance and focal length. If the subject moves during the pan, such as a boat bobbing or tree swaying, there'll almost certainly be some ghosting, while anything at close range may suffer from parallax effects. But zoom-out, keep your distance and the results can look wonderful. We've included two samples below: the first shows a best case scenario with a distant static landscape, while the second shows what happens when you try an incorporate a moving subject.

 
Sony Alpha SLT-A33 2D Sweep Panorama samples


Both images taken with 18-55mm at 18mm (27mm equivalent)
 

The 3D Panorama feature of the previous NEX models is also available on the SLT-A33, but now presented as an option in the Fn menu. This exploits the panning motion to generate depth information which can be interpreted by a compatible 3D TV over HDMI to deliver a 3D image. You also get a 16:9 image option along with the standard and wide sizes, although the maximum height of all three is 1080 pixels. In 3D Panorama mode, the SLT cameras record two files: a standard 2D JPEG which can be viewed and used as normal, and an accompanying MPO file which contains the depth information; the MPO files typically measure between 1 and 3MB each.

It sounds like an amazing feature, especially considering there's only one lens, but the conditions are stricter than the normal Sweep Panorama mode. First it's only available for horizontal pans from left to right or right to left. Secondly you'll need to get the panning speed just right or the SLTs will abort and ask you to try again.

 
 
 

Since the 3D mode creates a normal 2D JPEG image in addition to its dedicated MPO depth file, you might wonder why you wouldn't shoot all your panoramas in 3D mode for 'future-proofing'. Well you could, but the 3D mode shoots at a lower resolution than the normal 2D Panorama and is limited to horizontal pans, not to mention demanding a stricter motion. But if you're happy with a 1080 pixel height and carefully shooting all your panoramas horizontally, then you may as well opt for the 3D mode and enjoy their extra depth when connected to a 3D set.

Ultimately while the 3D effect is nowhere near as good as that of a decent 3D animated movie, it remains a fun and impressive capability, given there's only one lens on the camera. When the subject matter is right, the effect can look good, and is yet another unique string to the Alpha bow.

New to the SLT-A33's dial is the Continuous Advance Priority AE mode. This rather long description simply lets the camera shoot at a slightly higher continuous speed of 7fps where the only penalty is having to use the maximum aperture if the focus is set to Continuous. The reason the aperture is set to the maximum in this mode is to eliminate the need for it to open and close between frames. With it wide-open, the AF system can continuously autofocus without worrying about the aperture potentially closing down, leaving the shutter to fire as fast as it can.

The camera still faces the same buffer restrictions as when shooting in the normal Continuous High mode though, so you're looking at capturing no more than around 17 Large Fine JPEGs in a burst; the difference there though is doing so in around 2.4 seconds, which in our tests confirmed the quoted speed of 7fps.

Continuous shooting speed is an area where the SLT-A33 comfortably takes the lead over rivals like the Panasonic Lumix GH2. Not only does the A33 offer more confident continuous autofocusing, but it'll do it at its maximum quoted speed of 7fps, whereas the GH2 slowed to 2fps in our tests when tracking the action. Shame the 100% Live View system means following the action is difficult, but you can't have everything. We have more details about continuous shooting below.

Wrapping-up the exposure modes are the traditional PASM options on the dial. The SLT-A33 offers shutter speeds from 1/4000 to 30 seconds plus a Bulb option in Manual; the maximum flash sync speed is 1/160.

Adjusting the aperture and shutter speed in their respective Priority modes is as simple as turning the finger dial, although we were a little disappointed not to find Shift in Program mode - an annoying trend in Sony cameras. Exposure compensation is available in a +/-2EV range with 1/3EV increments.

Bracketing is available from the Drive menu with three frames taken in the choice of either 1/3 or 2/3EV increments. This may seem a little restrictive until you discover the built-in High Dynamic Range (HDR) option. White Balance bracketing is also available.


Sony Alpha SLT-A33 Continuous shooting

While other manufacturers traditionally reserve fast continuous shooting for their pricier cameras, Sony has been carving a very welcome niche for itself by offering very respectable frame rates on affordable models. The SLT-A33 is no exception, boasting 6fps continuous shooting, boostable to 7fps if you'll accept auto exposures and the aperture wide open.

 
 
 

At this price point there are of course further restrictions, most notably a fairly modest buffer which means you'll only be capturing around 15 best-quality JPEGs before the camera begins to stall. But the good news the SLT-A33 really can deliver its quoted frame rates for those short bursts.

When set to AF-S and fitted with a Memory Stick PRO Duo or Class 6 SDHC card, we fired-off 17 Large Fine JPEGs in just under three seconds, corresponding to a rate of approximately 6fps. Set to AF-C for continuous autofocus, the SLT-A33 slowed down a fraction to deliver around 5.5fps, but that's still very respectable for the money.

Switching to Standard quality JPEGs extended the buffer by a few shots, but still typically less than 20 in practice. The SLT-A33 alternatively offers a Continuous Low option which shoots at 2.5fps, although this again didn't extend the total number of frames by a great deal, stalling after around 25.

As mentioned above, there's also a quicker 7fps option. To select this you'll need to turn the SLT-A33's mode dial to Continuous Advance Priority AE, a rather long name that's mercifully shortened to a 7 icon on the dial. This switches the SLT-A33 to auto exposure with the aperture locked wide open to eliminate the time taken to adjust it between frames. In practice it really works too, delivering 7fps in our tests, albeit this time only for around seven frames in total.

So the SLT-A33 is limited by its buffer to short bursts, but at least it can deliver fast speeds during that time. This is in some contrast to Panasonic's Lumix GH2 which managed just 2fps with Continuous AF enabled.

This sounds like a big win for the SLT-A33 over its hybrid rival, but sadly neither are all that appropriate for fast action photography due to their reliance on Live View for composition. Like most cameras with 100% Live View systems, the image displayed between frames in continuous bursts is not actually live, but the previous image played-back. So while you have the shutter release held during a burst, you're actually looking at where the action was, not where it is right now.

This causes a problem when the action requires panning, as you have no feedback as to where to point the camera other than the previous photo you took - by which time the subject will of course have moved-on. As such, panning on live view systems involves a certain degree of blind anticipation and adjusting the camera further than the image you're viewing might suggest. It's something you do get used to, but it's nowhere as intuitive or easy as the optical viewfinder in a traditional DSLR which thanks to the speed of light gives a brief glimpse at what's happening between frames, allowing you to recompose as required.

But if the action is moving predictably, or straight towards or away from you, then the SLT-A33's 6 and 7fps continuous shooting modes are quite usable; they're also absolutely fine when shooting bursts in portraits to maximise your chance of capturing the right expression. The slower 2.5fps option also gives the SLT-A33 just enough time to display a live image between frames if preferred for instant feedback.

To see just how big an issue it is in practice, we took the SLT-A33 to photograph the famous Shotover Jet boats in Queenstown which race past at high speeds and perform 360 degree spins. As expected, it wasn't all that easy to keep the boat in the centre of a tight frame while panning, and if it deviated from a predictable straight path we frequently lost its extremities at the frame edges. Having roughly 15 frames at your disposal also meant you had to start shooting at just the right moment to avoid filling the buffer too early.

                 
       
                 
       
                 

But when the boats were moving predictably or spinning on the spot, we found we could keep the action centred even at the highest frame rates. And while the framing and tracking was no easier than the Panasonic Lumix GH2, the SLT-A33 at least managed to shoot up to 3.5 times quicker in our tests. Overall an impressive performance for a camera at this price point, although again if you're serious about shooting action, especially unpredictable subjects, you'll ultimately be better-off with a traditional DSLR.

Now it's time to check out the video recording capabilities in our Sony Alpha SLT-A33 Movie Mode page. Alternatively if you're not interested in movies, find out how the SLT-A33 compares against its rivals in terms of image quality in our results pages and sample images gallery. Or if you've already seen enough, head straight to our verdict.


All words, images, videos and layout, copyright 2005-2014 Gordon Laing. May not be used without permission.

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