我不能完全同意二位的意见。我同意就一台固定的数码相机来说，它的信噪比是固定的我们没法改变它。但是通过downsize from 8mp to 5mp，我可以同时减少信号和噪音（因为信噪比固定么）。我不care减少一些details，5mp is more than enough，我觉得噪音也会有相应的减少,which I'd be very happy to see.

我正在考虑拿下Canon S5 IS(new Costco price is irresistable)，noise is a big concern. How I hope S5 would stay with the original 6mp on S3 or even 5mp on S2! But I guess Canon is too smart to realize that there are consumers like me who'd care about the actual IQ more than the boasting of useless high MP, sigh...

我拿到S5以后会自己比较一下8mp和5mp或3mp的噪音水平。谢谢二位的inputs.