Sony Alpha A550

Noise Reduction (6.47)

Unlike most SLRs, which offer the option to turn high-ISO noise reduction off entirely to preserve the maximum level of image detail, the A550 offers only two choices here: high, which emphasizes image quality and normal, which prioritizes shooting speed). (Panasonic also prohibits turning high ISO noise reduction off entirely, though they do offer five levels to choose from). Given Sony’s take it or take a little less of it attitude, the question becomes ‘How well do the A550 photos capture fine image detail after the noise reduction system gets done with them?’ In our sample photos taken at high ISOs, we found the camera ramped up sharpening substantially as ISOs increased, producing images that do deliver fine detail, albeit in a field of colorful speckles.

The difference in processing kicks in at ISO 1600 and the higher setting does offer a small improvement at ISO 1600 and 3200, where the noise levels are still low enough to offer usable results.

We break out the levels for the component parts of image noise: red, green, blue, yellow and chroma (gray). If the noise in one channel spikes over the others it can cause a problem even when the overall noise level is relatively low. In this case, though, they are all grouped tightly together. More on how we test noise.

Image noise results were about average for a decent digital SLR. We don’t see a huge variation in this category, with the exception of the smaller-sensor Four Thirds and Micro Four Thirds models, which take a hit in the image noise category.

To test image noise levels, we shoot the ColorChecker chart under bright 3000 lux studio illumination, at all standard ISO levels and all available high-ISO noise reduction settings. (Low-light performance is tested separately). We use Imatest software to analyze the image noise levels under each test condition.

We ordinarily compare cameras with their noise reduction systems turned off entirely, but for both the Sony A550 and the Panasonic GF1 in the chart below, this wasn’t possible, since neither allows the user to disable high ISO noise reduction completely. Still, it’s interesting to note that both the Nikon D500 and the Canon T1i had about the same noise performance with noise reduction off as the Sony did at the Normal noise reduction setting.

With noise reduction for each camera set to its highest level, the Sony A550 has higher image noise than the comparison cameras at most ISO levels.

For overall noise performance, the Sony A550 falls slightly behind the Canon T1i here, but all three of the APS-C sensor SLRs posted roughly equivalent results, while the Olympus and Panasonic with their smaller sensors fell behind.

ISO Options

Available settings range from ISO 200 to an unusually high ISO 12800. There is also an Auto ISO setting, which is the only available mode when shooting in Auto or scene modes. Auto ISO is limited to the ISO 100-1600 range.

ISO Comparisons
Sony Alpha A550	Canon EOS Rebel T1i	Nikon D5000	Olympus E-30	Panasonic Lumix DMC-GF1
ISO Low
	ISO 100	ISO 200	ISO 100	ISO 100
	ISO 100	ISO 200	ISO 100	ISO 100
Sony Alpha A550	Canon EOS Rebel T1i	Nikon D5000	Olympus E-30	Panasonic Lumix DMC-GF1
ISO 200
Sony Alpha A550	Canon EOS Rebel T1i	Nikon D5000	Olympus E-30	Panasonic Lumix DMC-GF1
ISO 400
Sony Alpha A550	Canon EOS Rebel T1i	Nikon D5000	Olympus E-30	Panasonic Lumix DMC-GF1
ISO 800
Sony Alpha A550	Canon EOS Rebel T1i	Nikon D5000	Olympus E-30	Panasonic Lumix DMC-GF1
ISO 1600
Sony Alpha A550	Canon EOS Rebel T1i	Nikon D5000	Olympus E-30	Panasonic Lumix DMC-GF1
ISO 3200
Sony Alpha A550	Canon EOS Rebel T1i	Nikon D5000	Olympus E-30	Panasonic Lumix DMC-GF1
ISO 6400
Sony Alpha A550	Canon EOS Rebel T1i	Nikon D5000	Olympus E-30	Panasonic Lumix DMC-GF1
ISO 12800
Sony Alpha A550	Canon EOS Rebel T1i	Nikon D5000	Olympus E-30	Panasonic Lumix DMC-GF1

NOTE: The images above are not used in our testing or scoring, but are included here to show real-world examples of the differences between cameras at the various ISO settings.