[Mono]

I read on Russian forum that there is a callibration curve translating the picture shades to pixel shades.

It was possible to load to device a new curve. I am not sure if it was M92 or other Onyx product.

Generaly. It seems it is possible somehow to change the translation table (callibration curve). It is hard to say, if the behaviour, you discovered is intentional or it is sort of bug in table. In the case discussed at forum, there was by mistake in some readers wrong callibration curve and support helped the user to change it to right one.

Only Onyx could tell us, if this is a desired feature (making reading text easier) or some kind of mistake.

It is not an real issue for me, if I haven't noticed it untill now.

EDIT.
It looks like the output has only 14 shades, not 16 shades of display...