Compared to...

Studio scene comparison (higher sensitivities)

We've already looked in detail at the A550's high ISO performance in our the noise section of this review; here we're just taking a quick look at how the A550, Pentax K-7 and EOS 500D compare (at their default settings) when shooting our new studio setup at higher ISO settings - particularly in the shadow areas.

Note that due to increased noise in the shadows when it's turned on, this high ISO comparison has DRO turned off.

ISO 800

Sony Alpha 550
Canon EOS 500D
Pentax K7

ISO 1600

Sony Alpha 550
Canon EOS 500D
Pentax K7

ISO 3200

Sony Alpha 550
Canon EOS 500D
Pentax K7

ISO 6400

Sony Alpha 550
Canon EOS 500D
Pentax K7

ISO 12800

Sony Alpha 550
Canon EOS 500D

Most of the difference here is down to noise reduction: Pentax doesn't do a lot of it, Sony does, Canon sits somewhere in the middle. The difference in the end result at up to ISO 1600 isn't huge - and certainly won't impact on images viewed at normal magnifications. At ISO 3200 the Canon's output is a little less noisy and a little more detailed than the Alpha. At the highest settings the Sony outperforms the Pentax (it's easy to see why ISO 6400 isn't enabled by default), but only by throwing buckets of blurry noise reduction at the files, meaning the top two settings are firmly in the 'emergency use only' camp for all three cameras that go above ISO 3200.

It's worth noting that the Alpha 550's high ISO output (in JPEG mode) is considerably better than the A380 thanks to the less heavy-handed noise reduction.