At 1600 ISO the D300 is visibly suffering compared to the full-frame models. Noise artefacts are visible on all three cameras, but the full-framers are still retaining a high degree of detail whereas the D300 has become quite patchy in comparison. Again the amount of noise is similar on both the D700 and 5D, but the former’s result has less chroma noise and is preferred.
Increase to 3200 ISO and you’re at the top limit of the EOS 5D, at which point noise levels have become quite high. The D700 is also exhibiting quite apparent noise, but it’s cleaner than the 5D with fewer chroma artefacts. So the D700 is again preferred here, but the 5D has put in very good innings and proves it’s still a great camera for high sensitivity work. The D300 however is really suffering now with undesirable artefacts muddying the image and greatly reducing the detail. You can really see the difference between full frame and cropped frame bodies here.
At 6400 ISO, the story becomes even more apparent. The D700 sample is undoubtedly noisy, but at least there’s still plenty of detail and few coloured artefacts. In contrast the D300 at 6400 ISO really is a step too far.