Sony Alpha DSLR A900 High ISO NR Off		Sony Alpha DSLR A900 High ISO NR Low		Sony Alpha DSLR A900 High ISO NR Normal (default)		Sony Alpha DSLR A900 High ISO NR High
800 ISO		800 ISO		800 ISO		800 ISO
1600 ISO		1600 ISO		1600 ISO		1600 ISO
3200 ISO		3200 ISO		3200 ISO		3200 ISO
6400 ISO		6400 ISO		6400 ISO		6400 ISO

The Sony Alpha DSLR-A900 offers four different High ISO Noise Reduction settings: Off, Low, Normal (the default) and High. Each kicks-in at 1600 ISO or above. To compare their effect, we photographed our High ISO Noise composition at each of the four Noise Reduction settings – we’ve started our sequence below at 800 ISO to confirm the point at which noise reduction begins. The entire composition can be seen in the image left, and the crops are taken from an area in the very middle of the image.

The image above was taken with the Sony Alpha DSLR-A900 at a sensitivity of 800 ISO, using the Sony Carl Zeiss 24-70mm lens at 24mm f8; the original Large Fine JPEG file measured 7.21MB. Note, the A900 typically underexposed this image, so we applied +0.3EV to all the shots below.

Judging from the results below, noise reduction on the Sony A900 does indeed kick-in at 1600 ISO. From this point to the maximum 6400 ISO sensitivity, the Low and Normal settings deliver similar results, but the High setting applies noticeably greater noise reduction with obvious smearing of fine detail – there’s few who’d want to use it on the A900.

So with little difference between Low and Normal noise reduction, and the High setting looking poor, the interesting result here is with noise reduction switched-off altogether. In the left column you’ll see a noticeable increase in visible noise textures, and while the final sample at the maximum sensitivity is arguably irretrievable, the lower two settings could yield acceptable results in some situations with careful processing. Just don’t look too closely.

Now let’s have a look at some more real-life examples including several low-light indoor compositions in our Sony Alpha DSLR A900 sample images gallery.