The Z9 allows automatic compensation when shooting in full manual exposure mode and the f-stop changes when using a zoom lens. This can be set in Custom Settings Menu, item b7, and if turned ON you can choose whether shutter speed or ISO is varied to maintain same exposure.
With the new Z 600m f4 or the 400mm f2.8, there is no way to have this done automatically. If you are in manual exposure mode without auto ISO, then engaging the built in TC will result in a one stop underexposure, unless you manually dial in an exposure correction.
It would be nice if a future firmware update would allow the option of automatically correcting exposure when the TC is engaged.
With the new Z 600m f4 or the 400mm f2.8, there is no way to have this done automatically. If you are in manual exposure mode without auto ISO, then engaging the built in TC will result in a one stop underexposure, unless you manually dial in an exposure correction.
It would be nice if a future firmware update would allow the option of automatically correcting exposure when the TC is engaged.