Originally posted by Mistral75 My point remains anyway: there is no such thing as a contrast-AF sensor or contrast-AF sensor reference.
I agree that there is no "contrast-AF sensor".
One can make sense of "contrast-AF sensor reference", though.
We agree there is "contrast AF", i.e., the method of using any part of the imaging sensor to achieve AF by means of maximising (micro) contrast.
Now, "sensor reference" could refer to a "contrast level reference", i.e., a reference point regarding the amount of (local micro) contrast as achievable for a given lens on a particular sensor.
Better lenses can achieve higher levels of contrast on the imaging sensor and knowing a reference point of maximum contrast that is achievable on a particular sensor could help with optimising AF acquisition times. A normal feedback loop would always achieve maximum contrast (i.e., the best possible AF) after a while, but I'm assuming that it helps how far the contrast is away from a (normalised) optimum in order to drive the lens focus near the optimal region as quickly as possible.
It is also conceivable that there is a threshold value above which contrast AF will terminate, regardless of whether further iterations may produce even slightly better micro contrast. This could also be the "sensor reference" that needs to vary based on the lens.
I know that the above is speculation; I was just trying to read sense into the statement.
As to why some cameras receive updates and others not, maybe it is not always a question of whether the updated is "needed" but other considerations are at play?