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The Alpha SLT-A33 features a new Multi Frame Noise Reduction mode, which like Handheld Twilight, fires-off six frames in quick succession and stacks them into a single image in an attempt to lower noise levels. The big difference though is Multi Frame Noise Reduction can be applied at any sensitivity (including a new 25,600 ISO setting) and in any of the PASM modes. On this page we've put it to the test, comparing it against the normal single-frame ISO settings.

At 100 ISO, the SLT-A33 already delivers clean results with a single frame, making Multi Frame Noise Reduction at this sensitivity slightly redundant. Most would also agree the single frame taken at 200 ISO looks pretty good, but comparing it side-by-side with the Multi Frame Noise Reduction version reveals very subtle noise textures on the former, most obviously on the organ pipes. It's nothing to worry about at this point, but it is revealing to see a difference already, however minor.

At 400 ISO, the difference between the crops becomes more apparent. The single frame sample at 400 ISO remains respectable, but the noise textures on the organ pipes, not to mention around the foliage have become more obvious. In comparison, the Multi Frame Noise Reduction version appears bereft of these textures.

As the sensitivity increases, the differences become more obvious still. At 800 ISO, the single-frame shot is beginning to exhibit noise textures throughout, whereas the Multi Frame Noise Reduction version remains almost entirely clean. This is a great result for the A33 at this point.

With the sensitivity set to 1600 ISO we see the first signs of noise artefacts on the Multi Frame Noise Reduction sample. It's become noticeably less defined than before, but still enjoys an approximately two stop advantage over the single-frame version in quality.

The noise levels on both versions steadily increase with the sensitivity, and we'd say the gap narrows a little between 3200 and 12800 ISO, but the Multi Frame version remains at least one stop ahead in noise levels.

While the single-frame sensitivity tops-out at 12800 ISO, the Multi Frame options offer a higher setting of 25600 ISO. It certainly isn't pretty, but again is as good as the 12800 ISO sample from the single frame mode.

Overall, this is an excellent result for the SLT-A33. The Handheld Twilight mode gave us a tantalising glimpse into stacking frames for cleaner results, but annoyingly only offered it with automatic exposures and sensitivity. Now Multi Frame Noise Reduction lets you choose the ISO value and apply it in any of the PASM modes for total control over exposure.

The results here speak for themselves, with the Multi Frame Noise Reduction versions enjoying at least a one stop advantage over the single-frame shots, and for much of the range nearer to two stops. Obviously the technique of combining multiple frames only applies when the subject remains static (and the sound of a six-frame burst won't disturb), but in those situations, you'd be crazy not to select it on the A33. It more than makes up for the loss of sensitivity from the semi-reflective mirror and throws down the gauntlet to rival manufacturers. We certainly hope to see it deployed on all Sony models in the future.

Now it's time to check out our Sony A33 High Dynamic Range results page. Alternatively if you've already seen enough, head on over to our Sony Alpha SLT-A33 Sample Images Gallery for more examples across its sensitivity range, or head straight over to our verdict!

Sony Alpha SLT-A33 (JPEG using in-camera defaults) with Sony SAL1855 SAM		Sony Alpha SLT-A33 (Multi-frame Noise Reduction) with Sony SAL1855 SAM
100 ISO		100 ISO
200 ISO		200 ISO
400 ISO		400 ISO
800 ISO		800 ISO
1600 ISO		1600 ISO
3200 ISO		3200 ISO
6400 ISO		6400 ISO
12800 ISO		12800 ISO
25600 ISO not available		25600 ISO