wrote:
[]
Exposure adjustment by +1 fstop is the same as multiplication of the
data values by 2. Exposure adjustment by +2 fstop is the same as
multiplication of the data values by 4. So a linear operation. Just
the gradation of the aperture and the time dial is logarithmic, they
both affect to the data linearly.

You failed maths at school, didn't you?

I don't see how your statement follows from the first. In the linear
domain, adding two stops quadruples the light value, and the marking are
indeed log steps so that the ratio between f/2 and f/4 is the same as the
ratio between f/4 and f/8. The "time dial" steps are also log - a
geometric progression - 1 1/2 1/4 1/8 etc. although the markings are the
linear rather than the log values.

What am I missing, please?

David