I am not sure where you are getting your info on the D70's image quality at ISO 1600, but the one my friend uses is much noisier than my Pentax DS at even ISO 800, let alone ISO 1600. We have done many comparisons, and he is amazed at the low noise in my DS at high ISO compared to his Nikon.
You must be reading some reviews instead of doing actual comparisons!
That is the problem with some people; they simply prefer more NR with more lost of image details. The Nikon D70s has very low noise by default; so it doesn't need NR at high ISOs. Images captured by the Nikon D70s at ISO 1600 are well defined and crisp unlike on some other dSLRs. http://www.dpreview.com/reviews/koni...a7d/page18.asp
Here's one without NR at ISO 1600>>> http://www.imaging-resource.com/PROD...SLL1607XNR.HTM
With NR (And it is very conservative too)>>> http://www.imaging-resource.com/PROD...D70SLL1607.HTM
2 second exposures^
I could only find a comparison of the IST DS with the D50: (Should give you the idea anyway) (D70s' images are crisper and better defined at ISO 1600 than the D50)
Keep in mind that high ISO performance is not just low noise.Low noise is nothing; ultra compacts canalso have noise free images at ISO 1600.
Removing all the noise is not a good thing because noisecarries the details. Notethat the 1D Mark II series of the Canon professional dSLRs are having more noise in their images by default than the 2 & 3 digit consumer model versions. Photographers look at things differently from consumers...You may wonder why they prefer natural colors,non sharpened images, and less NR or none at all. (Some particularphotographers or proseven prefers a lighter AA filter over the image sensor to obtain crisp images by default)