Which factors are responsible for making a photograph zero noised when scaled to 100%?

Question

While purchasing a DSLR which factors should be kept in mind if your aim is to zoom your photograph to 100%, frame it, and hang it on a wall?

At 100% there shouldn't be ANY noise.

Answer

Noise is like death and taxes, it is unavoidable.

Even the most expensive cameras produce noise and, although, it may only be visible at 100%. The base ISO, usually between 100 and 200 is almost noise-free, but you will still see noise in images, particularly in shadow areas.

What strikes me as odd about your request is that 100% scale can give you very different print sizes depending on the camera and print resolution. If you print an image at 300 DPI from a 8 MP DSLR, you will give a MUCH smaller print than an image from a 24 MP DSLR printed at 180 DPI.

What happens to noise is that it gets averaged-out and becomes visibly diminished when images are scaled down, so if you have extra pixels and can afford to scale down for the print size you want, you will be better off in terms of noise.

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