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...
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.
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.
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.