Thanks of all the feedback, I'm a wee bitty lost when you say HCD does not have full coverage..........what does that mean in roughneck terms???
I'm used to shooting a Leica S and know that my 120 is not really a 120 but maybe a 90 but I'm really not sure why that is.
Sorry for what is probably going to sound like a dumb question??
It means that the image circle projected by the lens is too small compared to the size of the sensor.
It translates into corners that are unusable, either very dark and blurry, sometimes completely black.
Practically it means that you will have to crop the outer area of the image, turning your 100mp 40x54mm sensor into a ~80mp 36x48mm sensor and that you need to anticipate that when framing your images.
In fact those lenses may be able to cover a bit more than 36x48mm, so it may be more like 85mp, but they key point is to frame a bit wider.
Cheers,
Bernard