This is a great thread, thanks to the contributors!
Originally posted by Designosophy Yes, the lens determines the smoothness of what reaches the sensor, but the sensor's interpretation has an impact. I think that the difference between the K-5 and K-7 is greater with respect to color noise than luminosity noise, particularly at higher ISO. Another consideration for K-7 vs K-5 is low-ISO noise. The K-7 has some visible noise even at ISO 100 (when viewed at 100%). The K-5 has virtually no noise at its lowest ISO settings - 80 & 100. I can attest to the K-7 low-ISO noise myself.
Intersting note on the K-7 noise at ISO 100. I've noticed this myself and been a little irked by it. Good to hear this is negligible on the K-5. Have you noticed any banding or fixed pattern noise on the K-5? I can't shoot at or beyond ISO 3200 without seing some pattern noise pop out on my K-7.