Sony A900 High ISO NR

Sony A900 High ISO Image Quality

As noted elsewhere in this review, the Sony A900 offers four high-ISO noise-reduction settings, allowing you quite a bit of flexibility in choosing how you want to make the trade-off between subject detail and noise levels. Sony tells us that the "OFF" setting eliminates all inter-pixel NR processing, but the per-pixel NR that occurs on the sensor itself is always active. (See the Sony A900 Noise Reduction tab of this review for a detailed discussion of the two types of noise reduction processing.) We won't be able to independently confirm that the OFF setting really does turn off the High-ISO NR in the A900's RAW files until third-party RAW processing software is available that can process these files.

See for yourself how the noise reduction works under daylight lighting. Click on any of the crops below to see the corresponding full-sized image. Note that the A900 only starts applying High ISO NR at ISO 1,600, but we have included crops from lower ISOs as a reference.

The above table shows noise and detail levels at ISO 100 through 800, where the Sony A900 does not apply any High ISO Noise Reduction.

The above crops show the effects of the four levels of High ISO Noise Reduction available on the Sony A900. Discussions with Sony engineers suggest that the "OFF" setting for High ISO NR does in fact disable all inter-pixel NR processing. As discussed on the Sony A900 Noise Reduction tab, the per-pixel NR processing is still applied.

The crops above compare the Sony A900's JPEG High ISO performance (ISO 800 through 3,200) to that of the Canon EOS 1Ds Mark III, the previous, full-frame resolution king (21-megapixels). The Sony A900 may have bested it in terms of number of pixels, but it's clear that the 1Ds Mark III still holds a marked edge on high ISO performance. Note however that the Canon 1Ds Mark III does not offer ISO 6,400. (Also note that the Sony A900 is significantly less than half the cost of the 1Ds Mark III.)

The crops in the above table compare the Sony A900's RAW noise performance to that of the Canon 1Ds Mark III, across their entire ISO ranges. Click on the image to download the converted RAW file. These files were converted using dcraw, an excellent freeware RAW converter which applies no noise reduction or sharpening. (We found that Adobe Camera Raw still applies some limited noise-reduction when its NR settings are set to zero). The Sony RAW files were shoot with High ISO NR turned Off (and it goes without saying that the Canon RAW files are also without noise reduction). As you can see, the 1Ds Mark III has about a one-stop advantage in noise versus the Sony A900. That is, the Canon's noise at ISO 3200 is similar to the Sony's at ISO 1600, and so on. The Canon images also seem slightly more detailed at all ISOs. Both series were shot with the very sharp Sigma 70mm F2.8 EX DG Macro lens at f/8, using the same shutter speeds.