Sony A7R: ISO Performance
In Guide to Mirrorless is published a study of A7R image quality from ISO 50 through ISO 25,600. And also implicitly, dynamic range.
The scene chosen is a difficult one for any camera to handle (contrast and lighting skewed toward blue, though not nearly as challenging as spiky or extreme spectrum from many artificial lights, e.g., mercury vapor or strongly red tungsten lighting).
Noise behavior under perfect daylight or studio lighting is of modest relevance to many situations in which higher ISO is needed; all cameras can be made to look relatively good under ideal lighting. What matters to me in the field is how a camera handles real-world lighting, particularly the blue light of dusk and dawn and similar. And whether it can withstand a push or shadow boost. In that regard, a full-frame camera reigns supreme (short of medium format).
Sony Alpha A7R with Sony/Zeiss FE 35mm f/2.8 Sonnar ZA @ f/8
