Thank you very much for your answers, you have helped me
understand the theory but the practical remains a mystery. I am aware that my
question is more about photography than colour management but I believe the
answer is buried in colour management.
How can we explain the fact that the correct exposure of
a Kodak Q14 greyscale target, (correct exposure being defined as the exposure
that produces L*100 from the A patch (absolute white) and L*98 from the
neighbouring 1 patch (.10 less density)
also translates the Kodak 18% grey card as an RGB 145 signal which
becomes L* 60 in most assigned profiles if shot in jpeg via camera settings
and, L*70 if brought into camera Raw and processed through camera default
settings using the in-house input profiles and then a conversion to Adobe
RGB1998. ?
The exposure that translates the grey card as L*54 in
Adobe RGB 1998 produces L*93 from the A patch , translated from the native
control signal of RGB 232.
Obviously the cameras dynamic range is greater than the target but I
am perplexed by the fact that the same meter and grey card produce perfectly
exposed Ektachrome from the same target. Is there any way of explaining
why an
exposure taken from a meter-reading of a Kodak 18% grey card produces a
perfect slide of the Q14 target, yet and at the same time produces an
underexposed digital file that was exposed according to the premise that 18%
grey = L*54 in an 2.2 space?
My
results may very well be the product of some oversight or particularity but, it
appears as though digital capture requires a darker grey card.