Compared to...

The Pentax K-x is one of the standout performers in its class, and offers excellent image quality over a wide range of ISO settings. It can't quite match the EOS 550D in terms of resolution though - you can see for yourself the differences between these two cameras on this page.

Studio scene comparison (JPEG)

This is our standard studio scene comparison shot taken from exactly the same tripod position. Lighting: daylight simulation, >98% CRI. Crops are 100%. Ambient temperature was approximately 22°C (~72°F).

Canon EOS 550D vs. Pentax K-x

Camera settings:

• Canon EOS 550D: Canon EF 50 mm F1.4 lens, Aperture Priority, ISO 100
  JPEG Large/Fine, Manual WB, Default Parameters (Standard), Self-Timer, ALO off
  
  
• Pentax K-x: Pentax FA 50 mm F1.4 lens, Aperture Priority, ISO 100
  JPEG Large/Best, Manual WB, Default Parameters (Bright) Self-Timer
  

Canon EOS 550D	Pentax K-x
4.1 MB JPEG (3872 x 2592)	3MB JPEG (3872 x 2592)

Although it might sound like a rather obvious point, the main difference between default JPEG output from the EOS 550D and Pentax K-x is that the 550D's files are larger. There is very little difference in actual detail resolution, although the slightly more aggressive sharpening being applied by the 550D makes detail a little more obvious. Closer examination reveals that the K-x can resolve almost as much of the finest detail in this scene, but it is slightly masked by the fractionally softer default output.