He claims that when a picture is downsized that the D800 will have better high ISO performance than the D700 at the same resolution. Does this make sense?
From his blog post.
Now here comes the big question – does a high resolution sensor mean bad low-light capabilities? If you look at a picture at 100%, then yes, a high resolution sensor always translates to more noise at higher ISOs. However, when the image is down-sampled to smaller resolution, those differences are significantly reduced. For example, when you look at a 12 MP image at ISO 3200 at 100% and then look at a 36 MP image at the same ISO at 100%, you will surely see more noise on the latter image. However, if you down-sample the 36 MP image to 12 MP, then the 36 MP image is actually going to come out cleaner than the 12 MP image. In addition, if you had a slight focus issue on both, the 36 MP image would look sharper when down-sampled to 12 MP. What I am trying to say here, is that you should not be scared of a high resolution D800, thinking that it will be in any way inferior to your beloved D700. I will provide an in-depth analysis between the D700 and the upcoming D800 when I have it on my hands, but I can say with confidence now that the D800 will give better results than the D700 when its image is down-sampled to 12 MP. Overall, we should be getting around a full stop of advantage noise-wise with the D800 compared to the D700. Think of it this way – you will be able to get superb 36 MP images in daylight and you have the option to down-sample images to lower resolution in low-light.