ISO Sensitivity / Noise levels (contd.)

Noise reduction compared

One of our biggest concerns with the Alpha 700 was that even in raw mode the camera was applying a noticeable amount of noise reduction that had the effect of smearing fine detail at higher ISO settings. After scores of complaints about this 'not completely raw' issue Sony, to its credit, released a firmware upgrade for the A700 that allows the high ISO noise reduction (in JPEG and RAW modes) to be turned down or turned off altogether, and the A900 gets the same options.

To check the effect of noise and noise reduction on low contrast detail we shoot our most glamorous member of staff in relatively low light and look at a 100% crop (as shown above). With the ISO 200 RAW version as a reference point we can easily see any smearing of low contrast detail (hair) as we move up the ISO range.

Raw vs JPEG low contrast detail comparison: ISO 200 - 800

The Alpha 900's user-selectable 'High ISO Noise Reduction' option doesn't kick in until you get above ISO 800, so in the crops below you'll find comparisons of the camera's default JPEG output and the same shot processed through Adobe Camera Raw (4.6) using default settings (except for noise reduction, which is set to zero). As you can see there's a little more detail in the raw version (the camera obviously does apply a little noise reduction even at ISO 400).

ISO 200 JPEG	ISO 200 RAW
ISO 400 JPEG	ISO 400 RAW
ISO 800 JPEG	ISO 800 RAW

Raw Noise Reduction settings comparison: ISO 1600-6400

In each of the cases below the RAW file was processed using Adobe Camera Raw (4.6) with the noise reduction options both set to zero. As a comparison we've also included a crop from the JPEG output using the camera's default settings (NR 'standard'). As you can see the noise reduction still affects the raw files (as it did with the Alpha 700), and even at the standard setting results in a noticeable loss of fine low contrast detail. Fortunately the OFF setting appears to remove all noise reduction - this means visibly noisier results, but results that have more fine detail (allowing you to do whatever you want with noise reduction in post processing)

What's also obvious from these crops is that whilst ISO 1600 is perfectly usable (shooting raw and dealing with the noise yourself), things are a little less impressive at ISO 3200 and especially at ISO 6400, when noise is so extreme that there is little advantage to shooting with the noise reduction turned off.

ISO 1600 Noise reduction comparison
ISO 1600 JPEG - NR Standard	ISO 1600 RAW NR Off
ISO 1600 RAW NR Standard	ISO 1600 RAW NR High
ISO 3200 Noise reduction comparison
ISO 3200 JPEG - NR Standard	ISO 3200 RAW NR Off
ISO 3200 RAW NR Standard	ISO 3200 RAW NR High
ISO 6400 Noise reduction comparison
ISO 6400 JPEG - NR Standard	ISO 6400 RAW NR Off
ISO 6400 RAW NR Standard	ISO 6400 RAW NR High