Would a Ec-CIV focusing screen from a 1DMkIII work on a 1dMkIIn that normally uses a Ec-CIII screen without any issues? I know that there is a custom function setting within the 1D that you are able to choose your focusing screen in but this is where my confusion comes in.
On the 1DMkIIn menu it does not have an option for the CIV.
On the 1DMkIII menu it has an option for the CIV and it is a separate option from the CIII screen.
What sort of issues would I experience if I used the CIV in the 2n?