This iea comes from the logic of output size. If you are presenting your final work at 8x10 size, or on the web at 1800x1200, then comparing images as they would be used at your final size makes perfect sense. There are VERY few people who will need the full resolution of a D800.
If you plan on printing 20x30s, then a D800 is great for you.
>As to the question of downsizing, what I had meant was that I >do not want to compare the digital noise after reducing the >resolution of the D800. Maybe you could educate me further on >this. I often read that if you downsize the image from a >high-resolution camera and then compare the digital noise to >another lower resolution model, you may not find much >difference and so on and so forth. My way of thinking is that >(and may be this is where I am wrong and you are right), it >seems odd to have a high resolution camera and then reduce the >resolution when it comes to comparing the noise. When we >compare the image quality, we compare it at full resolution >(for example, we say that image quality from a D800 is >superior to that from a D700; at that time we do not say that >we are comparing the D800's image quality at 12MP resolution >to a D700, which is also 12MP). I hope you have understood my >logic (right or wrong) and would be very pleased to hear from >you. > >Regards.