See also Jan 7 entry. I have an extensive noise study in the works (for DAP) comparing the Nikon D3x, D3, Canon EOS 1Ds Mark III and EOS 5D Mark II. In it, I’ll address what the real world issues are from ISO 50 through ISO 25,600.
It’s taken me longer than I’d have liked for a few reasons—shooting and analysis take considerable time and effort, and I found enough interesting issues that required exploration that I re-shot my original tests to confirm some very interesting findings.
Even at low ISO values, noise is relevant, especially if you’re a fine-arts photographer looking for clean blacks, and extracting detail in darker areas (see Noise and Multiple Exposures). The example below shows horizontal streaks, and this is at ISO 100! ISO 50 fares little better. Some cameras do this, even medium format cameras, and some do not.
Pattern Noise (streaks) at ISO 100
My exploration of noise is not going to offer the naive shot of the Macbeth color checker card often seen (though I include one). Nor are the mathematical noise graphs of much use in understanding how a camera behaves with real images—the issues of banding/streaking, how very dark areas perform, usable dynamic range and color rendition in dark areas all come into play in a complex way, which makes it important to treat the subject fairly across multiple cameras.
Unfortunately life often deals some setbacks and my writeup has been delayed due to recent illness, so publication has been pushed back a bit.