Studio scene comparison (RAW)

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

Nikon D90 (RAW) vs. Pentax K20D (RAW)

Nikon D90
Pentax K20D
2.9 MB JPEG (4288 x 2848)
4.0 MB (4672 x 3104)

Going further to support the idea that the D90 might have quite a strong AA filter, the slightly higher-resolution output from the K20D is showing more detail but the main difference is in the per-pixel-sharpness (acutance).