DSLR sensors are physically larger than the sensors used compact cameras, this is why they tend to be less prone to digital noise. I know that the D70 is pretty good up to 400ISO. Noise becomes more of a problem with long (very long) exposures of say 2 minuets or more. That said noise can at times add to an image if you are looking for a grainy type image. I have shot at 1600 and 3200 ISO with the 10D even at 3200 it is usable in some situations. I have got a 1600 ISO shot somewhere in my gallery, I will see if I can find it. To get back on topic a little I think that from 100-200 etc equates to the equivalent of 1 stop of light and so on. (I could stand corrected on that)

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