With its use of translucent mirror technology in the Alpha 33, Sony has evolved the way that its digital cameras focus. But how much does the new system really improve on the SLR? We put the Sony Alpha 33 to the test

Product Overview

Overall rating:

Sony Alpha 33

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LCD viewfinder:
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Sony Alpha 33 review


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Sony Alpha 33 at a glance:

  • 14.2 million effective pixels
  • 7fps continuous shooting
  • New 15-point 
AF system
  • New 1,200-zone evaluative metering system
  • Street price: £569.99 for body only

It seems at odds with an apparently ‘forward-thinking’ camera industry that Sony should look to an idea from the past to solve a problem in the present. Yet that 
is exactly what the company has done 
with its new Alpha 33 and Alpha 55 SLT (single-lens translucent) cameras.

The problem centres on how to the improve the phase-detection autofocus system to make it faster between shots and allow it to work in Live View or video capture modes. Sony’s solution is, in fact, the evolution of an idea first used by Canon in 1965, when it introduced the Canon Pellix.

Instead of a moving mirror in the Pellix SLR, Canon designed and used a pellicle mirror (see Geoffrey Crawley explains… on pages 58-59 of this issue), which was fixed into position. This very thin mirror split the light that entered the camera, redirecting a portion to the viewfinder while letting the rest through to expose the film. The camera wasn’t a success, as the amount of light reaching the viewfinder made it dark and difficult to focus. Although in the 1980s and ’90s a small number of professional SLRs were fitted with pellicle mirrors, the technology was largely forgotten – until recently.

With the introduction of video capture, DSLR manufacturers face the problem of how to focus the lens without the use of the usual AF system. Phase-detection focus relies on a camera mirror being down to reflect light to an AF sensor. However, that mirror has to be flipped up in video-capture mode so the image-focusing light can reach the sensor. Until now, the only way to focus during video capture has been either to focus manually or to use contrast-detection focus, which is comparably slow and fidgety.Sony is the last of the major DSLR manufacturers to introduce video in its cameras, with the company insisting that it wanted to give users the same experience when focusing during video capture as when taking still images. This meant making continuous phase detection possible.

The answer to the implementation of phase detection during video capture comes in the form of Sony’s translucent mirror technology (TMT). As with a pellicle mirror, this uses a piece of glass with a metal coating that is fixed in position in the Alpha 33 and its sibling, the Alpha 55. The mirror lets around 70% of light through it, while reflecting the remaining 30% to the phase-detection AF sensor. This allows phase detection to be uninterrupted, regardless of whether the camera is in Live View or video-capture mode.

However, the benefits of TMT don’t stop there. With no moving mirror (and no film wind-on mechanism) the shooting rate can be increased significantly – the Alpha 33 offering up to 7fps, and the Alpha 55 up to 10fps while still autofocusing.

Having learnt from the Canon Pellix, Sony has resolved the problem of a dark viewfinder by replacing the optical unit with a 1.15-million-dot (equivalent) electronic viewfinder.

With the removal of the mirror box and reflex system for the viewfinder, the Alpha 33 and Alpha 55 are no longer SLR cameras. Instead, they are described by Sony as SLT or single-lens translucent cameras. Consequentially, I was keen to find out exactly where the Sony Alpha 33 camera would sit within the Alpha range.

  1. 1. Introduction
  2. 2. Features
  3. 3. 7fps shooting rate
  4. 4. Build and handling
  5. 5. White balance and colour
  6. 6. Metering
  7. 7. Autofocus
  8. 8. Noise, resolution and sensitivity
  9. 9. Dynamic range
  10. 10. Viewfinder, live view, LCD and video
  11. 11. The competition
  12. 12. Our verdict
Page 1 of 12 - Show Full List
  • Ian Barton

    I would like this camera for weddings because of its low light capabilities,speed I don’t really need,
    16 mp is plenty for what I won’t ,if I could buy a D800 with 16 mp in raw I would probably buy this instead.I understand 36.3 mp would be great for cropping and still having detail but I don’t shoot in a studio so don’t really need it, as far as video goes, I have no interest atall and is something I dont want.

  • Ian Alexander

    Buy a secondhand D3s and save your money.Nikon made a boo boo with this camera.Two different memory card slots! The noise levels are no better than a D3s.The 11fps can not auto focus between frames so your back to 9fps same as the D3s and has other restrictions.Sooner the D4s arrives the better. Nikon are Falling way behind Canon now.

  • Mas

    I just came across your awomese blog!I am slowly delving into the world/language of photography, as I love taking pictures of my children and nature.I do not have dslr, but a nice point and shoot. I SO hope to get a dslr for my birthday.I cannot wait to learn from your site and participate when I can seeing as I don’t have a dslr yet.Thank you so much for this wonderful resource!

  • Jonathan Siddall

    Camera body feels very comfy to hold and every button is well placed.
    Have shot on the camera for over 6 hours non stop and no aching hands.
    Weather proofing is excellent, took it out in the rain and no problems.
    Extremely solid build.

    Every option and setting you are likely to need is on the body.
    Very quick to make changes to autofocus, bracketing, iso, quality, fstop, shutter speed, focal point, white balance.

    Iso Range is incredible, used it for indoor equine events in low light where no
    flash is allowed. You can rock at iso 6400 1/250-/400 f5.6 no problem, hard to see any noise at all.
    Camera noise is noticeable at iso128000 !!
    When auto iso is enabled it nails it about 98% of the time, which is impressive when shooting
    in very changeable light conditions.
    Tested auto iso out in Manual mode at an outdoor equine event and was Hugely impressed.

    AutoFocus is super fast and highly accurate.
    Simple to use, hold the button in on the left and you get all the options you will ever need.
    afc 9 points is perfect for sports with predictive movents.
    It locks on faster than you can blink !
    In large burst shots the focus is perfect on each image.
    afc 21 is good for birds with un predictable motion
    afs does an amazing job for portraits, products and landscapes.
    It is easy to change mode and clearly displayed in the eyepiece.
    Moving the focal point is easy peasy with the 2 joysticks.

    Image Quality is excellent in Jpeg fine and even better in uncompressed RAW.
    The level of detail is fantastic.
    Accurate colors, tones and highlights look spot on.
    Even with some major pixel peeping the detail is awesome.
    HDR in RAW is mindblowingly good. Not tried the automatic HDR.
    Auto white balance does a great job in most situations.
    Color settings are impressive, Portrait does make skin tones look fantastic.
    Landscape gives you nice skies and greens.
    Monochrome is beautifull black and white.

    XQD is very fast, downloading images via USB3 is such a time saver.
    CF you do have to use the reccomended cards, i tried a none recommend card that is fast and it showed
    error. The Extreme pro worked perfect.
    Buffer on this camera is extreme, never had a camera shoot so many shots so fast.

    LCD Screen detail is very good, works well in bright sunshine.
    Resolution is amazing.
    The Expeed 3 Processor is rapid, reviewing images is super fast.
    It flies through the menus with ease.
    You press a button and get an immediate responce, no lag at all.
    MY menu option is usefull and simple to customise.

    DX lenses work well in DX crop mode, trade off is you loose some of the sensor size
    Image Quality is still excellent.
    Battery life is very good, shooting from 9am to 7pm at a show jumping event, no flash
    3-5 shot bursts, reviewing and deleting images. Lasted the whole day with plenty of power to spare.

    Tested with XQD card, High quality, 70-200mm f2.8 and 35mm prime f1.8 lenses
    on f5.6
    Full Frame is dissapointing. 1920×1080 30p
    Even on a prime lens the video looks soft

    2.7 Crop, Video looks sharp and smooth.
    The autofocus for moving subjects often goes out of focus
    This is most dissapointing if you are going to use this camera for filming work.
    While filming sport i often ended up going to manual focus and the camera lost focus.
    Not good enough for the money.
    I hope Nikon will fix this soon with a firmware update !

    This is a fanstastic stills camera, one of the best.
    The video needs improvement. looks great on 2.7 crop.
    Very glad i bought this for pro photography
    Its fantastic.