Recently a very professional photographer who shoots stunning pictures told me that the best images can be obtained from digital cameras at ISO 200. He also stated that this is what all the manufacturers (Nikon, Sony, Canon, ...) say.
He explained it something like this (I heavily paraphrase as my amateur brain does not remember the correct technical terms used): The light is taken in by the sensor as is at ISO 200. At higher values the signal is amplified (which I understand is correct). At lower values like 100 however, the signal is artificially diminished, which leads to bleeding(?) of the pixels. Therefore ISO lower than 200 is only to be used for extreme lighting situations like shooting a solar eclipse.
However, I could not find any information corroborating these claims. I also checked a couple manuals of high-end DSLRs. They did not contain any mention of such a manufacturer's recommendation. I also took some comparison shots with my own digital camera (Lumix) and found ISO 100 to produce better, lower-noise results.
Now I'm at a loss as what to make of that man's statement?