Circle The Wagons - Here Come The Native ISO's
The answer to this question sometimes depends on which side of he conversation you are on. ie. Don't ask General Sheridan and expect a comfortable answer...
In the case of the native ISO of digital cameras, this seems to be fixed around the 160-200 mark. I suspect that it is a characteristic of the actual component and is a function of the composition of the silicon layer and whatever the current state of division thereof. I have discovered that these sensors are manufactured by a very few companies - and in many cases well-known camera companies are using sensors that are manufactured by business rivals.
And they are all perfectly okay with this as each manufacturer takes the sensor and then does different things with the signal - one optimises it for one thing and one for another.
I was apprised of this by reading a book this weekend - " Mastering the Fujifilm X-E1 and X-Pro1 " by Rico Pfirstinger. It is a Rockynook book obtainable at Boffins Bookstore in William Street.
In the chapter that deals with ISO settings it makes the point that the native ISO of the two cameras it deals with is 200, and the camera always takes its picture at this 200 - even if you set it to ISO 1600 or higher. What it is doing to present you with a picture at that higher ISO is underexposing the image and then dealing with that underexposure through software. And apparently doing it very well.
This strikes me as true of all of them, and explains the improved characteristics of each new model of camera from any one manufacturer - they are not adding a new sensor in many cases - just re-writing the mathematics of the signal processing. Then I realised I was not reading carefully enough...
Fujifilm has a different sensor from others - it really does have a different pattern of receptor sites from most of the others, and can benefit users greatly in the way of resolution and clarity. The X-trans sensor may very well be quite different indeed. But I take it that it still looks at the world at 200 ISO and then just shuffles the electrons to get up to a clean 6400.
Who'da thunk it?