wrote:
snip
That notwithstanding, I'm curious about reciprocity with digital
sensors, if only to know what is going on a bit better. Is there a
point at which doubling the exposure time doesn't produce a "one stop"
change, as with film? Or makes a color change?
snip
Greg Guarino


The silver halide particles in film must absorb 2 photons
within a short time interval for the particle to become a
silver metal particle in development. That is the cause of
reciprocity failure, and it does not happen with a digital
sensor. When a sensor pixel has reached the point where it
can't hold more charge, it is said to be saturated. Near
there, doubling the exposure time will produce less of a
change. Saturation also occurs with film. It is not
reciprocity failure.